Tubular plant cover and use thereof for pre-cultivation and planting of forest and fruit trees

Abstract

A tubular plant cover (10) for pre-cultivating and planting forestry and fruit trees has an opening at each of its opposite ends and, in between along a longitudinal axis (16), a wall (18) made of biodegradable material, which, with an inner circumferential surface, defines a cavity for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the plant cover. The wall comprises first and second wall sections (24, 26) a) of different wall thicknesses, which alternate along the longitudinal axis between the openings and / or in a direction radial to the longitudinal axis and / or in a circumferential direction around the longitudinal axis, as seen in section, or b) of different materials that biodegrade at different rates.The smaller wall thickness - or the faster biodegradable material - ensures target decomposition points (25), at which wall breakthroughs (35) first occur during the biodegradation of the plant cover, while the larger wall thickness - or the slower biodegradable material - stiffens the plant cover.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to a tubular planting sleeve for pre-cultivating and planting forestry and fruit trees, which has an opening at each of its opposite ends and, in between along a longitudinal axis, a wall made of biodegradable material, which, with an inner circumferential surface, defines a cavity for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the planting sleeve, according to the preamble of patent claim 1. In particular, the invention relates to such a planting sleeve as is intended for mass use in tree nurseries for forestry and fruit trees. Furthermore, the invention relates to the use of such a tubular planting sleeve for pre-cultivating and planting forestry and fruit trees. BACKGROUND OF THE INVENTION AND STATE OF THE ART

[0002] Maintaining the productivity of forest areas and expanding forest cover through reforestation of previously forest-free areas is considered to be of great importance for the Earth's carbon dioxide balance. In addition to natural regeneration combined with the sowing of deciduous trees in open-growing areas, the planting of drought-resistant, thermophilic, and economically valuable tree species is important for this.

[0003] Currently used standard forestry planting practices utilize a one- or multi-year pre-culture in a nursery to produce seedlings. The development of the seed or germ into a productive, fast-growing, competitive plant takes place under controlled and optimized conditions, thus avoiding the significant risks associated with direct sowing—desiccation of seedlings and seed consumption by birds and mammals. The seed savings associated with planting are also of great importance, for example, for sessile oaks and English oaks, since sufficient seed quantities for establishing stands by seed are only available in years with good fruiting for these species.

[0004] In recent decades, pre-cultivated container plants have increasingly been used for forest stand establishment. Reusable pallets of substrate-filled, hard-walled plastic containers, such as those described in the publication DE 36 38 312 A1, have proven effective for their cultivation.

[0005] In addition, various so-called "soft-wall containers" made of textile fabric, plastic plant pots, and substrate-filled foil bags are used for the pre-cultivation of agricultural, horticultural, or forestry plant material. When the plants are planted in the soil with these pre-cultivation containers, i.e., the pre-cultivation containers remain in the forest soil, for example, the pre-cultivation containers are increasingly made of compostable thermoplastics to avoid plastic waste.

[0006] In this context, WO 2022 / 253782 A1, which forms the preamble of patent claim 1, discloses a container for pre-cultivating and planting forest trees, which container is formed from a pipe segment. This container is intended to provide optimal growth conditions for the plant germ until a vital main root forms and is to be used immediately after the pre-cultivation phase for planting the plants in the open field, for example, when establishing a forest stand. The design of a plantable pre-cultivation container as an elongated pipe segment enables the root of the young plant to already have a considerable depth extension upon planting.

[0007] More specifically, the vessel disclosed in WO 2022 / 253782 A1 is formed from a biodegradable, preferably isodiametric, and open-ended pipe segment, has a stable wall impermeable to liquid water, and has a length of between 25 and 40 cm and a width of between 4 and 7 cm. The vessel is filled with a three-phase, low-solids, water-storing substrate in the form of a viscoelastic, moist particle mass, which has a water-binding particle content of over 50 percent by volume and an air content of at least 15 percent by volume, with an adhesive water content of at least 50 percent by volume.

[0008] As a preferred, specific embodiment, this prior art proposes a compostable tube segment in the form of a commercially available cylindrical shipping sleeve made of hard paper, which is combined with a film tube section made of a thin-walled, compostable, thermoplastic material. The film tube section is guided through the shipping sleeve and then pulled over the outer side of the shipping sleeve on both sides of the shipping sleeve, so that the hard paper wall of the shipping sleeve is covered inside and out, and the two ends of the film tube section overlap on the outer side of the hard paper wall.With such a design of the pipe segment, the cylindrical shipping sleeve made of hard paper ensures sufficient stability of the pipe segment during pre-culture, while the film tube section is intended to protect the shipping sleeve made of hard paper against penetrating water and to seal the wall of the pipe segment from the inside and outside.

[0009] Although this type of tube segment design appears to be entirely suitable for research and testing purposes, it does pose certain risks if the tube segment is to be used on an industrial scale, for example, in the semi-automated cultivation of large quantities of seedlings. If, for example, the enveloping film tube section is damaged during filling or transport of the tube segment, there is a risk that the hard paper shipping sleeve will absorb water and subsequently soften earlier than planned, possibly even collapsing, meaning it is no longer sufficiently mechanically strong or rigid. Upright transport and / or mechanical planting of the seedlings in the tube segment would then no longer be possible.A similar problem can be expected if the pipe segment is accidentally filled and stored the wrong way round, i.e., with the end of the film tube section overlapping the outside of the pipe segment facing upwards. In this case, too, irrigation water, for example, could penetrate unhindered through the collar formed by the outer end of the film tube section and soften the hard paper shipping sleeve.

[0010] Similar containers and the problems associated with them are also known from document EP 0 097 735 A1. This prior art proposes so-called “plant stumps”, i.e. essentially cylindrical casings made of a material that dissolves in the soil, such as paper, plastic film or the like, which are filled with soil, peat or a substrate that enables and / or promotes growth and in which a seed is embedded. In order to address the problem already identified in this prior art of plant stumps no longer being stable when moist, the stumps are combined directly to form a package of several plant stumps, in which the plant stumps are tied together tightly and thus support one another. These plant stump packages can also be used upright for cultivation in the greenhouse when the walls of the individual plant stumps are no longer able to support themselves.

[0011] Since with this state of the art it is not possible to control when and where the walls of the individual planting stumps will dissolve, it is further proposed that a shim, intermediate layer or similar made of a non-dissolving material be inserted between planting stumps grouped together in a package at the points where premature dissolution of the planting stumps is to be prevented. This barrier, which is to be removed later, i.e. before planting, is also intended to prevent the individual root balls of adjacent planting stumps from "felting" together during the pre-cultivation, i.e. from growing into one another and thus forming a single root ball. With this state of the art, after the planting stumps have been separated, for which the shim, intermediate layer or similar has to be removed with a certain amount of effort, it can be assumed that the walls of the planting stumps are no longer mechanically stable after the pre-cultivation and are also no longer suitable for retaining water.In addition, the rather mushy or doughy consistency of the individual, already partially decomposed plant stumps makes them difficult to handle during transport and planting. TASK

[0012] Compared to the described prior art, the object of the invention is to create a tubular plant cover for pre-cultivation and planting of forest and fruit trees that can be mass-produced as cost-effectively as possible and with a comparatively low material expenditure, which generally addresses the disadvantages of the prior art described above and specifically has a wall that is sufficiently stable for a standing pre-culture, a subsequent standing transport and the application into the planting soil, which is also optimized with regard to the formation of a preferably vital root structure from a plant germ and whose decomposition behavior can be easily adjusted depending on the application (plant species, degree of pre-cultivation), climate and soil conditions of the location.The task is also to form a main root that is as vital as possible from a plant germ that is embedded in a substrate contained in the tubular plant cover. DESCRIPTION OF THE INVENTION

[0013] The above objects are achieved by a tubular plant cover having the features of patent claim 1 and the use thereof for pre-cultivating and planting forest and fruit trees according to patent claim 15. Advantageous embodiments of the invention are the subject of the dependent patent claims.

[0014] In the case of a tubular planting sleeve for the pre-cultivation and planting of forest and fruit trees, which has an opening at each of the opposite ends and, in between along a longitudinal axis, a wall made of biodegradable material, which, with an inner circumferential surface, defines a cavity for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the planting sleeve;According to the invention, the wall comprises first and second wall sections made of different materials which are biodegradable at different rates, or of different wall thicknesses, which alternate along the longitudinal axis between the openings and / or in a radial direction relative to the longitudinal axis and / or in a circumferential direction around the longitudinal axis when viewed in section, wherein the more rapidly biodegradable material or a smaller wall thickness of the wall provides predetermined decomposition points at which breakthroughs in the wall first occur during the degradation of the plant cover, while the more slowly biodegradable material or a greater wall thickness of the wall stiffens the plant cover.

[0015] When "forestry and fruit trees" are mentioned in connection with the present invention, this particularly includes oaks, beeches, chestnuts, Douglas firs, pines and black walnut trees as forestry trees, and apple, cherry, pear and plum trees as fruit trees. Furthermore, a "plant germ" within the meaning of the present invention is generally understood to mean a "seed", such as an apple core, a chestnut or an acorn. However, depending on the degree of pre-cultivation of the respective plant, the term plant germ should also include "seedlings", i.e. already germinated seeds, such as a germinated acorn, "seedlings", i.e. seedlings that have formed their first leaf shoots, and "saplings", which, compared to seedlings, already have further leaf shoots.

[0016] The tubular plant casing according to the invention is generally adaptable and suitable for the cultivation of seedlings from smaller seeds, such as apple seeds, from larger seeds, such as acorns, beechnuts or chestnuts, as well as from sprouts and seedlings. Furthermore, the tubular plant casing according to the invention is also fundamentally adaptable and suitable for the cultivation of seedlings from "cuttings", which are therefore also intended to be included in the term "plant germ". By definition, cuttings are parts of plant shoots that are cut off for the purpose of vegetative propagation and inserted into a culture substrate filled into the tubular plant casing to develop their own roots. The tubular plant casing according to the invention can therefore advantageously be used in a variety of ways for the pre-cultivation and planting of forestry and fruit trees.

[0017] With regard to the "substrate", i.e. the filling of the tubular planting casing with a mixture of sphagnum thalli, hemp shives, etc. with or without the addition of lime or potassium bicarbonate, as well as the actual process for growing the seedling from the plant germ, reference is expressly made at this point to the generic document WO 2022 / 253782 A1, since the present invention is primarily concerned with the structure and function of the tubular planting casing as such.

[0018] In other words, a basic idea of ​​the invention is to form the wall of the tubular plant cover from mutually different wall sections, of which the first wall section is intended to promote the formation of desired decomposition sites with resulting breakthroughs over time, while the second wall section primarily serves to stiffen the wall. In the context of the present invention, "desired decomposition sites" in / on the first wall section are understood to mean wall areas where a decomposition attack is desired and where, due to the local formation of the wall or its material properties, very good starting conditions for a decomposition attack exist.

[0019] The second wall section of the tubular planting sleeve, on the other hand, is advantageously designed to be mechanically stable, strong, or rigid enough that the tubular planting sleeve has a sufficiently stable wall, allowing for easy upright pre-cultivation, upright transport (even after pre-cultivation), and / or mechanical planting of the young plant contained in the tubular planting sleeve into the planting soil. It is consciously accepted that the planting sleeve decomposes more slowly in the area of ​​the second wall section than in the area of ​​the first wall section, and consequently, parts of the second wall section remain in the planting soil or are detectable longer than parts of the first wall section.

[0020] Since the mechanical stability of the tubular plant cover is largely ensured by the second wall section, the first wall section can be optimized so that wall breakthroughs occur at the desired decomposition points in a controlled manner at the right time with regard to the life cycle of the tubular plant cover. Apart from the ends of the tubular plant cover, the decomposition attack on the wall initially only occurs in a radial direction, i.e. predominantly perpendicular to the wall from the inside out and from the outside in. The breakthroughs in the wall that first occur at the desired decomposition points in the first wall section then mean that the decomposition attack on the wall also occurs in the surface extension directions of the wall, with decomposition attack components parallel and circumferential with respect to the longitudinal axis of the tubular plant cover.As a result, the wall in the wall areas adjacent to the openings is no longer only attacked from two opposite sides, but also “from the direction of the opening”.

[0021] Because the first wall section and the second wall section alternate, viewed in section, along the longitudinal axis between the openings and / or in a radial direction relative to the longitudinal axis and / or in a circumferential direction around the longitudinal axis, a defined distribution of the target decomposition sites on the wall is advantageously achieved. Compared to a plant cover with a homogeneously formed wall, this results in a better controllable, possibly more uniform, and more efficient decomposition attack on the wall of the tubular plant cover. This is particularly conducive to good adjustability of the decomposition behavior of the tubular plant cover, depending on the respective application specifications and conditions (plant species, degree of pre-cultivation, climate, soil conditions at the site of use, etc.).

[0022] Depending on the type of plant to be grown in the tubular plant cover and / or the environmental conditions expected at the later location, it may also be advantageous if small openings are created in the wall during the pre-cultivation and / or if the wall of the tubular plant cover is specifically perforated for the pre-cultivation - hereinafter also referred to as openings for the sake of simplicity.

[0023] The perforations in the wall of the tubular plant cover promote better root growth of the respective plant during its pre-cultivation in two ways: Firstly, the perforations promote good permeability and aeration of the substrate in the tubular plant cover, allowing growth-promoting bacteria to provide more nutrients to the plant. Secondly, the perforations significantly improve root quality.

[0024] More precisely, the seedling first forms a taproot which grows downwards towards the open end of the tubular planting cover and comes into contact with the ambient air upon emerging from the tubular planting cover. This is where a process known as “air pruning” occurs, during which the end of the taproot exposed to the air dehydrates, stopping vertical root growth and encouraging branching of the taproot towards the seedling. When the new branches extending from the sides of the taproot then encounter the perforations in the wall, the branching is once again stopped in the particularly well-ventilated areas and encouraging the formation of further sub-branches. This process is repeated with each new root which finds its way to a perforation, so that the plant quickly develops a vital root structure with a mass extending outwards or inwards.downward-directed, fibrous roots with many more root tips.

[0025] Through these root tips, the plant can then absorb more nutrients and water, which stimulates faster growth. Furthermore, the root structure, consisting of numerous straight branches, facilitates the establishment of the seedling after planting. If the lower opening of the tubular planting sleeve and the openings in the wall are covered with soil at this stage, the fine root tips can pass through the lower opening or the increasingly widening openings directly toward the surrounding soil.

[0026] Thus, the tubular plant cover according to the invention can also be advantageously optimized with regard to the formation of a vital root structure from a plant germ by a corresponding structural design of the first and second wall sections.

[0027] To achieve the functions of the two wall sections discussed above, the invention provides two structural alternatives: In the first structural alternative of the invention, the wall has alternating first and second wall sections that have different wall thicknesses. Due to the smaller wall thickness of the first wall section, the perforations occur first at the intended decomposition points without jeopardizing the mechanical stability of the tubular plant cover. In the second structural alternative of the invention, however, alternating first and second wall sections made of different materials are provided, which biodegrade at different rates, whereby the previously described effect can also be achieved.

[0028] The two structural alternatives mentioned above can be realized cost-effectively and with a comparatively low material expenditure, so that a tubular planting cover predestined for mass production is created for the pre-cultivation and planting of forest and fruit trees.

[0029] The above-mentioned second structural alternative of the invention, according to which a more rapidly biodegradable material is combined with a more slowly biodegradable material in the tubular plant cover, is particularly suitable when, for example, the desired mechanical properties cannot be achieved with a material preferred in terms of decomposition behavior due to wall sections of different wall thicknesses. In this second structural alternative, the wall is preferably formed by a profile co-extruded from the various materials, which is wound helically and overlappingly around the longitudinal axis of the tubular plant cover at longitudinal edges that are essentially wedge-shaped when viewed in cross-section, wherein the second wall section made of the more slowly biodegradable material is fully or at least partially embedded in the first wall section made of the more rapidly biodegradable material.In another, equally conceivable embodiment of this second structural alternative, the second wall section made of the more slowly biodegradable material can also be wound over or onto the first wall section made of the more quickly biodegradable material for reinforcement and glued or welded to it, which is, however, less preferred with regard to the most efficient and cost-effective production of the tubular plant cover.

[0030] To form the above-mentioned first structural alternative of the invention, in which the wall has first and second wall sections which have different wall thicknesses, the three variants described in more detail below are preferred, which differ fundamentally from one another with regard to the manufacturing process.

[0031] In a first manufacturing variant, the wall of the tubular plant cover preferably consists of a strip or profile of predetermined width, which is wound helically and partially overlapping around the longitudinal axis, wherein the strip or profile forms the second wall section of greater wall thickness in the area of ​​overlap and the first wall section of smaller wall thickness adjacent to it. The helical overlap area with double wall thickness gives the tubular plant cover its mechanical stability, so that a wall of the tubular plant cover wound in this way advantageously has high flexural and torsional rigidity while being lightweight. Furthermore, such a wall can be manufactured as a continuous product with lengths of 3 to 4 meters per minute using a relatively fast process that is easily implemented on an industrial scale.In this process, the mechanical properties of the wall of the tubular plant cover and its decomposition rate can be easily and effectively adjusted by varying the width of the band or profile, the wall thickness of the band or profile and the width of the overlap.

[0032] A further advantage of this first manufacturing variant is that when the tape or profile is wound over the inside of the tubular plant cover, a helical groove is created which forms a receiving space for the filling of the tubular plant cover, which advantageously leads to a claw or positive engagement of the filling with the wall, so that the filling is held in the tubular plant cover in a virtually slip-resistant manner.

[0033] With a view to achieving the most efficient, continuous production possible, it is preferred if, in the area of ​​overlap with respect to the longitudinal axis, an outer side of the strip or profile is glued or welded to an inner side of the strip or profile - which also applies to the area of ​​overlap in the above-discussed profile of the second structural alternative, which is co-extruded and wound from materials of different biodegradability. One advantage of such a material-to-material connection is its potential impermeability, so that no water can escape through the wall of the tubular plant cover, which consequently does not have to be bound or retained in the substrate. For materials that are not suitable for direct welding - e.g.While conventional methods (e.g., using the residual heat of the extrudate during winding) are suitable, bonding, in which a biodegradable adhesive is introduced into the overlap area during winding, offers a viable alternative to welding on an industrial scale. Designs are also conceivable in which the wall cohesion is achieved by means of adhesion or a positive fit, whether in a "macrogeometric" sense - e.g., through steps in the wall material created by a fixed angle of the strip or profile, through an additional component such as a thread during sewing, etc. - or in a "microgeometric" sense - for example, through mechanical clamping or "velcro" in the overlap area if the surface of the wall material is sufficiently rough.

[0034] Tests on tubular plant covers with an outer diameter of approximately 50 mm, which are particularly suitable for reforestation, have shown that the ratio of the width of the second wall section of greater wall thickness, which runs helically around the longitudinal axis, to the width of the first wall section of smaller wall thickness, which runs helically around the longitudinal axis, should preferably be in a range between 1 / 16 and 12 / 1. A ratio of 1 / 16 represents the smallest possible overlap, while the first wall section of smaller wall thickness is at its maximum width - and vice versa for a ratio of 12 / 1. In principle, the smaller the overlap, the faster the tubular plant cover decomposes, but the more fragile the tubular plant cover is. Rapid decomposition is, for example,This is advantageous when cultivating shallow-rooted plants - as opposed to tap-rooted plants - because the more roots break through the wall of the tubular planting cover, the faster they can grow radially out. In contrast, the narrower the first wall section with a smaller wall thickness, the longer the decomposition takes, but the more stable the tubular planting cover is. While the increased stability associated with the greater overlap reduces the likelihood of larger breaks occurring in the wall of the tubular planting cover, this type of tubular planting cover retains water better and is suitable for longer-term pre-cultivation. Ultimately, a suitable compromise must be found depending on the application (plant species, degree of pre-cultivation), climate, and soil conditions at the location.

[0035] In specific, expedient embodiments of the tubular plant cover, it can be provided, for example, that the width of the first wall section running helically around the longitudinal axis, measured in the width direction of the wound strip or profile, is between 1.5 mm and 20.0 mm and / or that the width of the second wall section running helically around the longitudinal axis, measured in the width direction of the wound strip or profile, is between 0.5 mm and 9.0 mm.

[0036] In a second manufacturing variant of the first structural alternative of the tubular plant cover, which can advantageously be produced particularly quickly on an industrial scale, the wall of the tubular plant cover can have a substantially rectangular wave-shaped contour when viewed in a longitudinal section, which is formed from a tubular base body by means of a blow molding process, so that radially inner and radially outer, second wall sections of greater wall thickness are formed with respect to and substantially parallel to the longitudinal axis, which are connected to one another via first wall sections of smaller wall thickness, which extend in a substantially radial direction with respect to the longitudinal axis.

[0037] In the blow molding manufacturing process, a heated, plastically deformable preform or a not yet solidified, tubular extrudate made of a base material with a wall that is of equal thickness at every point in the circumferential and longitudinal directions is introduced into a tool that forms a negative contour and can be divided into at least two halves. Pressurized from the inside by means of a gas, e.g. air, such that the preform or extrudate expands under the pressure, comes into contact with the negative contour of the tool and thereby reproduces or molds it. After solidification, the tool can be divided and the tubular plant cover removed.

[0038] With this general preface to blow molding processes, various process variants can be used to produce the tubular plant cover in terms of effort and throughput. In the process variant, which is simpler in terms of equipment and therefore more cost-effective for smaller batch sizes, individual blow molds can be used as tools to produce individual, essentially closed hollow bodies as semi-finished products. In a subsequent step, these hollow bodies are then trimmed at both ends transversely to the longitudinal axis to achieve the tubular shape of the plant cover.

[0039] In the more complex process variant, a so-called "corrugator" can be used to manufacture continuous products. In the corrugator process, a tube is first extruded and calibrated, which is then immediately formed between the tools into an endless, tubular semi-finished product. The tools for this are designed as endlessly circulating chains with mold jaws / mold halves that travel with the tube. In a subsequent step, the solidified, endless semi-finished product is cut to length to form the tubular plant sleeves. This latter process variant is particularly predestined for industrial-scale production, as speeds of 6 to 10 meters of semi-finished product per minute can be achieved, which is conducive to the very economical mass production of tubular plant sleeves.

[0040] In these blow molding processes, the desired wall thicknesses of the first and second wall sections—and thus indirectly the decomposition rate and stability of the tubular plant cover—can be achieved by appropriately selecting the wall thickness of the base material and the geometry of the negative contour of the tool, which in turn results in defined expansions of the base material during blow molding. While the radially outer second wall sections are pushed and displaced outward during blow molding—with a wall thickness that remains essentially constant compared to the radially inner second wall sections—the first wall sections connecting the second wall sections to one another stretch, stretching the base material in a direction essentially radial to the longitudinal axis.With increasing radial expansion of the first wall sections, their thickness decreases, the first wall sections therefore taper accordingly, which ensures predetermined decomposition points of the tubular plant cover, at which, according to the invention, breakthroughs in the wall first occur.

[0041] Compared to the wound first production variant discussed above, the blow-molding production of the tubular plant cover according to the second production variant is, of course, associated with a higher investment requirement in terms of equipment, so that the second production variant generally requires higher quantities in terms of its economic efficiency.

[0042] In specific, expedient embodiments of the blow-molded second production variant, for example for tubular plant covers with an outer diameter of approximately 50 mm, the ratio of the height of the first wall sections with a smaller wall thickness in the direction transverse to the longitudinal axis to the length of the second wall sections with a greater wall thickness in the direction of the longitudinal axis can be between 1 / 2 and 2 / 1. The basic rule is: the higher the first wall sections with a smaller wall thickness in the direction transverse to the longitudinal axis and / or the shorter the second wall sections with a greater wall thickness in the direction of the longitudinal axis, the faster the tubular plant cover decomposes. In contrast, the lower the first wall sections with a smaller wall thickness in the direction transverse to the longitudinal axis and / or the longer the second wall sections with a greater wall thickness in the direction of the longitudinal axis, the more stable the tubular plant cover is.Here, too, a suitable compromise must be found for the tubular plant cover to be mass-produced, depending on the application (plant species, degree of pre-cultivation), climate and soil conditions of the site.

[0043] In a third manufacturing variant of the first structural alternative of the tubular plant cover, which is again easier to adapt with regard to the dimensions of the plant cover and its decomposition rate, the wall is rolled from at least one sheet of biodegradable material around the longitudinal axis to form a substantially cylindrical cavity or a substantially frustoconical cavity, wherein overlapping, interconnected sheet edge regions form at least one second wall section of greater wall thickness, to which at least one first wall section of smaller wall thickness adjoins in the circumferential direction around the longitudinal axis.

[0044] This third manufacturing variant, which is advantageously easy to implement with comparatively little equipment effort, is particularly suitable for very small series of tubular plant covers in special formats and / or with a special conical shape deviating from the cylindrical (standard) shape, which cannot be produced using the other manufacturing processes mentioned above, or can only be produced to a very limited extent. Tubular plant covers with special formats, especially those with a large diameter, can be easily manufactured by joining several sheets of biodegradable material. The rigidity of the tubular plant cover can also be easily adapted to specific requirements by using several sheets of biodegradable material.

[0045] A further advantage of the tubular plant sleeve in the third production variant is that it offers greater variability when it comes to filling the tubular plant sleeve with substrate and plant germ. This means that the plant sleeve can be filled either before or after the curved edge areas have been connected to the substrate and the plant germ. If, for example, a seedling with an already established root structure is to be introduced into the plant sleeve, its roots can first be carefully laid out together with the substrate on the sheet or sheets of biodegradable material and then - like tobacco in cigarette paper - rolled or wrapped into the sheet or sheets, only then are the curved edge areas connected. However, it is also possible to first form the cylindrical or truncated cone-shaped hollow body by rolling the sheet or sheets.of the arches of biodegradable material and connecting the arch edge areas and only then filling the tubular planting cover thus formed with substrate and plant germ, as in the other manufacturing variants described above.

[0046] In a preferred embodiment of the tubular plant cover according to the third manufacturing variant, an outer side of the arch can be glued or welded to an inner side of the arch in the area where the interconnected arch edge regions overlap with respect to the longitudinal axis. This is particularly easy to accomplish, in addition to the advantages of such a material connection already discussed above. Alternatively, the arch edge regions can also be joined by sewing, velcro, or similar methods, analogous to the joining techniques discussed above for the other manufacturing variants.

[0047] From the tests already mentioned above with tubular plant covers, in particular with an outer diameter of approximately 50 mm, the following absolute and relative design rules have proven to be practical and appropriate, and apply equally to all manufacturing variants of the tubular plant cover according to the first structural alternative: Particularly with regard to good decomposition behavior, the ratio of the smaller wall thickness of the first wall section of the wall to the average diameter of the inner peripheral surface of the wall should preferably be in a range of 1:250 to 1:25. Regarding the absolute values ​​of the wall thickness, the smaller wall thickness of the first wall section of the wall should be greater than or equal to 0.2 mm and less than or equal to 2.0 mm.

[0048] Furthermore, it has proven practical if the ratio of the smaller wall thickness of the first wall section to the larger wall thickness of the second wall section lies in a range of 1:1.1 to 1:3.0. Depending on the stability requirements of the respective application, a sufficient section modulus against bending and torsion can be set in this way; the area moment of inertia of the tube cross-section, which is relevant for buckling, can also be adjusted within this framework. In this case, the wall thicknesses for the larger ratio are more easily achieved with blow-molded tubular plant covers, while the wall thicknesses for the smaller ratio are feasible, for example, with glued versions of the first and third production variants, if the thickness of a layer of adhesive is added to the doubled smaller wall thickness.

[0049] For all embodiments, the wall surfaces of the tubular plant cover can, in principle, be smooth. However, particularly with regard to ensuring good adhesion of the substrate contained in the tubular plant cover, it is preferred if the average surface roughness on the inner circumferential surface of the wall is greater than or equal to 20 µm and less than or equal to 120 µm. Depending on the surface roughness, water can also adhere better to / at the wall of the tubular plant cover, which advantageously promotes decomposition of the biodegradable material of the wall.

[0050] To direct the growth of the root of the plant germ accommodated in the tubular plant casing in a substantially vertical direction, the tubular plant casing can optionally be configured such that at least two, preferably four, ribs are formed on the wall, projecting radially inward in the direction of the longitudinal axis and extending substantially parallel to the longitudinal axis. These ribs serve as root orientation aids for the vital main root to be formed. Such a measure advantageously hinders or prevents a circumferential "wandering movement" of the root on the inner circumferential surface of the tubular plant casing.

[0051] In all embodiments, such ribs in the biodegradable material of the wall can be formed in a simple manner, e.g., by means of a hot-stamping process, particularly after the plant cover has been formed into its tubular shape, whether by winding, blow molding, or rolling. In the blow-molded, tubular plant cover according to the second manufacturing variant, such ribs can also be formed from a tubular base body together with the essentially rectangular wave-shaped contour of the wall in a particularly simple and rapid manner by means of blow molding.

[0052] Depending on the manufacturing process and subsequent conditions of use, different requirements are placed on the materials to be selected for the wall of the tubular plant cover, which must be weighed against each other. Basically, the materials must first be suitable for the area of ​​application, e.g. they must not be toxic to the plants or the (forest) soil. In addition, low moisture permeability is desired, and decomposition or biological degradation should not occur too quickly or too slowly in the expected biological environment. Furthermore, the biodegradable material of the wall of the tubular plant cover should be selected so that the plant cover is sufficiently robust from the time the sphagnum is filled in until it is inserted into the (forest) soil. At the same time, the plant cover should have the lowest possible weight, also with regard to the costs incurred during production and transport.Particularly with a view to keeping production costs as low as possible, it is also desirable to minimize material usage during production, maintain relatively low material costs, and ensure good market availability. From a sustainability perspective, it also makes sense to maximize the proportion of bio-based components, as the plant covers are a single-use product that remains in the (forest) soil after planting and therefore cannot be recycled. Last but not least, the biodegradable material of the wall must be readily processable in the respective process used to manufacture the plant covers.

[0053] Therefore, when selecting the biodegradable material for the wall, it is important to find a compromise that meets a variety of requirements as best as possible. The tests conducted have shown it to be advantageous if the biodegradable material or materials for the wall are preferably selected from a group comprising the following materials: polybutylene succinate-co-butylene adipate (PBSA), polyhydroxyalkanoate (PHA), cellulose acetate, natural polymers such as starch, polylactic acid compounds (PLA compounds), and polybutylene adipate terephthalate (PBAT). In addition to these plastics, natural polymers without chemical conversion can also be used as biodegradable material for the wall of the tubular plant cover, such as those produced by Lactips SA., France, if the above-mentioned compromise that best meets the various requirements can be found with these materials.

[0054] In this context, the generic term “PHA” refers in particular to materials made from the following building blocks: Polyhydroxybutyrate (PHB, often abbreviated to P3HB), a linear thermoplastic polymer with very high crystallinity, which is, however, very brittle and is therefore rarely used in its pure form; Polyhydroxybutyrate-co-3-valerate (PHBV), in which, in addition to the butyrate, another building block, the valerate, is incorporated into the polymer at a low content, resulting in a polymer that is still very brittle and highly crystalline, but also forms a very good oxygen barrier; Polyhydroxybutyra-co-3-hydroxyhexanoate (PHBHHX), in which a significantly longer molecule, the hexanoate, is incorporated as the second PHA building block, which gives the material significantly greater flexibility and a wider processing window;Poly3-hydroxybutyrate-co-4-hydroxybutyrate (P3HB-4HB), whose two hydroxybutyrate building blocks differ in where the linkage takes place on the respective molecule, and with which a variety of properties can be adjusted - for example, in one material over 30% of the 4HB building block is used to produce amorphous and highly elastic PHAs.

[0055] Finally, it may be desirable under certain circumstances to influence the degradation behavior of the tubular plant casing by adding lime or potassium bicarbonate. In this context, tests were conducted with tubular plant casings made of different materials. Plant casings whose walls were made of certain thermoplastic compounds decomposed significantly more slowly under the influence of moist white peat or sphagnum substrates without the neutralizing addition of lime or potassium bicarbonate than with the aforementioned additives (e.g., PBSA). Thus, plant casings made of some of the materials tested retained their mechanical stability and external integrity in a pre-culture lasting up to 5 months, provided the pH did not exceed 5.5. This is important for the practical introduction of tubular plant casings.For example, the decomposition of the planting casings can be inhibited by a low pH value during planting production and activated after planting by raising the pH value. There are various ways to increase the pH in the planting casing substrate shortly before or after planting, or during planting production, for example, by sponge-in finely dispersed lime or by adding biodegradable plant residues with a high ash content.

[0056] On the other hand, plant casings tested, whose walls were made of other materials (e.g., polylactic acid compounds), showed significantly faster biodegradation when pre-cultured with a moist sphagnum substrate without added lime than when pre-cultured with added lime. This result can also be used in practice to inhibit biodegradation of the plant casings during the seedling production phase and their subsequent activation. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The invention will be explained in more detail below using preferred embodiments with reference to the accompanying, partially schematic drawings. Starting with the second embodiment, the reference numerals are assigned to the respective embodiment by their first digit ("1" for the second embodiment, "2" for the third embodiment, etc.), while the second and third digits denote identical or corresponding parts or sections with the same numbers as the first embodiment. The drawings show: Fig. 1 is a side view of a tubular plant cover according to a first embodiment of the invention, with a wall formed from a band wound helically and partially overlapping around a longitudinal axis, so that the wall has first and second wall sections of different wall thicknesses; Fig. 2 a (longitudinal) sectional view of the tubular plant cover according to the first embodiment according to Fig. 1 according to the section line II-II in Fig. 1; Fig. 3 an enlarged view of detail III in Fig. 2, which better illustrates the different wall thicknesses of the wall sections; Fig. 4 a side view of a tubular plant cover according to a second embodiment of the invention, with a wall which is formed from a tubular base body by means of a blow molding process, so that the wall has first and second wall sections of different wall thicknesses; Fig. 5 a (longitudinal) sectional view of the tubular plant cover according to the second embodiment according to Fig. 4 according to the section line VV in Fig. 4, to illustrate the essentially rectangular wave-shaped contour of the wall in section; Fig. 6 an enlarged view of detail VI in Fig. 5, which illustrates that radially inner and radially outer second wall sections of greater wall thickness are formed with respect to and substantially parallel to the longitudinal axis, which are connected to one another via first wall sections of smaller wall thickness; Fig. 7 a perspective view obliquely from the top right of a tubular plant cover according to a third embodiment of the invention, with a wall which, according to the second embodiment according to the Fig. 4 to 6 is formed from a tubular base body by means of a blow molding process, so that the wall not only has first and second wall sections of different wall thickness, but also four ribs projecting radially inwards in the direction of the longitudinal axis and extending substantially parallel to the longitudinal axis, which serve as root orientation aids; Fig. 8 a side view of the tubular plant cover according to the third embodiment according to Fig. 7; Fig. 9 a (longitudinal) sectional view of the tubular plant cover according to the third embodiment according to Fig. 7 according to the section line IX-IX in Fig. 8; Fig. 10 a (cross) sectional view of the tubular plant cover according to the third embodiment according to Fig. 7 according to the cutting line XX in Fig. 8; Fig. 11 an enlarged view of detail XI in Fig. 9, for a better illustration of the different wall thicknesses of the wall sections; Fig. 12 an enlarged view of detail XII in Fig. 10; Fig. 13 is a plan view of a tubular plant cover according to a fourth embodiment of the invention, with a wall which is rolled from a sheet of biodegradable material around the longitudinal axis to form a substantially cylindrical cavity, so that overlapping, interconnected sheet edge regions form a second wall section of greater wall thickness, which is adjoined by a first wall section of smaller wall thickness viewed in the circumferential direction around the longitudinal axis; Fig. 14 a side view of the tubular plant cover according to the fourth embodiment according to Fig. 13, with a view of the second wall section of greater wall thickness; Fig. 15 a (cross) sectional view of the tubular plant cover according to the fourth embodiment according to Fig. 13 according to the section line XV-XV in Fig. 14; Fig. 16 an enlarged view of detail XVI in Fig. 15, for a better illustration of different wall thicknesses at the first and second wall sections; Fig. 17 is a bottom view of a tubular plant cover according to a fifth embodiment of the invention, with a wall which is rolled from a sheet of biodegradable material to form a substantially frustoconical cavity around the longitudinal axis, so that the tubular plant cover has first and second wall sections of different wall thicknesses according to the fourth embodiment according to the Fig. 13 to 16; Fig. 18 a side view of the tubular plant cover according to the fifth embodiment according to Fig. 17; Fig. 19 a (cross) sectional view of the tubular plant cover according to the fifth embodiment according to Fig. 17 according to the section line XIX-XIX in Fig. 18; Fig. 20 an enlarged view of detail XX in Fig. 19, for a better illustration of different wall thicknesses at the first and second wall sections; Fig. 21 a side view of the tubular plant cover, broken up and down, according to the Fig. 1 to 3, which is shown in an upright position according to its intended use, for visualising a (partial) decomposition state of the plant cover, in which openings have already formed at the intended decomposition points of the wall on the first wall section with a smaller wall thickness; Fig. 22 is a (longitudinal) sectional view, broken off to the sides and downwards, of a tubular plant cover according to a sixth embodiment of the invention, with a wall having first and second wall sections made of different materials that are biodegradable at different rates; Fig. 23 a (longitudinal) sectional view, broken off to the sides and downwards, of a tubular plant cover according to a first variant of the sixth embodiment according to Fig. 22; and Fig. 24 a (longitudinal) sectional view, broken off to the sides and downwards, of a tubular plant cover according to a second variant of the sixth embodiment according to Fig. 22.

[0058] In all figures, the contents (substrate, plant germ, plant roots, depending on the degree of pre-cultivation) of the respective tubular plant cover have not been shown, because this is not necessary for understanding the structural design of the plant cover as such, which is the focus here. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] In the Fig. 1 to 3 and 21, a tubular planting sleeve for pre-cultivating and planting forest and fruit trees according to a first embodiment is generally designated by the reference numeral 10; in accordance with the above note, the tubular planting sleeve is provided with the reference numerals 110 (second embodiment), 210 (third embodiment), 310 (fourth embodiment), 410 (fifth embodiment) and 510 (sixth embodiment) in other embodiments shown in the further figures.

[0060] The tubular plant cover 10 has an opening 12, 14 at each of its opposite ends and, along a longitudinal axis 16, a wall 18 made of biodegradable material between them. The wall 18, with an inner circumferential surface 20, defines a cavity 22 for receiving a plant germ embedded in a substrate—both not shown in the figures, but already described in more detail above, also with reference to the prior art according to WO 2022 / 253782 A1, to which explicit reference is again made at this point—wherein a vital main root (also not shown) is to be formed from the plant germ in the tubular plant cover 10. Relevant details of the use of the tubular plant cover 10 for pre-cultivation and planting of forest and fruit trees can also be found in the cited prior art.

[0061] As best described in detail according to the Fig. 3, the wall 18 comprises, according to an important feature of the first embodiment, first and second wall sections 24, 26 of different wall thicknesses T1, T2, which in this embodiment alternate along the longitudinal axis 16 between the openings 12, 14 as seen in section. The smaller wall thickness T1 of the wall 18 provides for desired decomposition points 25 - see the Fig. 21, which shows a section of the tubular plant cover 10, broken off at the top and bottom, in its vertical functional position - at which openings 35 first appear in the wall 18 during the biodegradation of the plant cover 10. These openings 35, as already described at the beginning, not only cause a controlled decomposition of the plant cover 10, but also promote plant growth in the plant cover 10. Corresponding target decomposition points and openings are also provided for in the other exemplary embodiments, as will be explained in more detail below, or these arise there as a result of the biodegradation of the wall of the tubular plant cover, although this is not specifically shown in the associated figures to simplify the illustration. The greater wall thickness T2 of the wall 18, on the other hand, mechanically stiffens the plant cover 10 during pre-cultivation, during transport, and when planting the pre-grown young plant.

[0062] How best to Fig. 3, the wall 18 in the first embodiment consists of a band 28 (or profile) of predetermined width B, which in a first manufacturing variant is wound helically and partially overlapping (overlap 30) around the longitudinal axis 16. In the area of ​​the overlap 30, the band 28 forms the second wall section 26 of greater wall thickness T2 and, adjacent thereto, the first wall section 24 of smaller wall thickness T1. While the first wall section 24 of smaller wall thickness T1 has a width B1, the second wall section 26 has a width B2, as in Fig. 3 can be seen.

[0063] In this exemplary embodiment, an outer side 32 of the band 28 is welded to an inner side 34 of the band 28 in the area of ​​the overlap 30, as viewed with respect to the longitudinal axis 16. For this purpose, the band 28 made of the biodegradable material is drawn diagonally from a nozzle of an extruder by means of a rotating mandrel (device details not shown in the figures), whereby the hot, i.e. still thermoplastic material of the band 28 is deposited or applied in an overlapping manner on the mandrel under a contact pressure caused by the tensile stress such that it welds in the areas of the overlap 30 due to the residual heat of the material without any additional external energy supply. As an alternative, bonding with a suitable adhesive is of course also possible at this point.

[0064] In this way, continuous production of the wall 18 is possible; the finished tubular plant covers 10 are then obtained by cutting the solidified (continuous) wall 18 into (tubular) pieces of, for example, 300 mm in length. As a result, the band 28 in this exemplary embodiment forms a first wall section 24 extending helically or spirally around the longitudinal axis 16 and a second wall section 26 also extending in the form of a cylindrical spiral around the longitudinal axis 16, wherein the width B1 of the first wall section 24 plus twice the width B2 of the second wall section 26 corresponds to the total width B of the band 28.

[0065] The relative dimensions of the tubular plant cover 10 are selected such that the ratio of the width B2 of the second wall section 26, which extends helically around the longitudinal axis 16, to the width B1 of the first wall section 24, which extends helically around the longitudinal axis 16, measured in the width direction of the wound band 28 (or profile), generally lies in a range between 1 / 16 and 12 / 1. In the specific embodiment, this ratio is 1 / 2.15.

[0066] As far as the relative wall thicknesses are concerned, the tubular plant cover 10 is dimensioned such that the ratio of the smaller wall thickness T1 of the first wall section 24 of the wall 18 to the average diameter D (see Fig. 2) of the inner peripheral surface 20 of the wall 18 generally lies in a range of 1:250 to 1:25. In the illustrated embodiment, this ratio is 1:100.

[0067] Finally, the ratio of the different wall thicknesses to each other, i.e. the ratio of the smaller wall thickness T1 of the first wall section 24 to the larger wall thickness T2 of the second wall section 26, is generally in a range from 1 : 1.1 to 1 : 3.0. Fig. In the tubular plant cover 10 shown in Figures 1 to 3 and 21, this ratio is specifically 1:2.

[0068] Of course, these dimensions also depend on the biodegradable material used for the wall 18, as well as on the method by which the tubular plant cover 10 is manufactured. The specified ranges were determined in experiments in which the materials already explained in more detail above were tested as biodegradable material for the wall 18 of the tubular plant cover 10.

[0069] As far as the absolute dimensions of the tubular plant cover 10 are concerned, it can be stated that the width B1 of the first wall section 24, which runs helically around the longitudinal axis 16, measured in the width direction of the wound strip 28 (or profile), is generally between 1.5 mm and 20.0 mm. In the specific exemplary embodiment, in which a compound of PBSA, PBAT, and fillers was used as the material, the first wall section 24 is 7.5 mm wide. The width B2 of the second wall section 26, which runs helically around the longitudinal axis 16, measured in the width direction of the wound strip 28 (or profile), in contrast, is generally between 0.5 mm and 9.0 mm, here approximately 3.5 mm. Finally, the smaller wall thickness T1 of the first wall section 24 of the wall 18 is generally greater than or equal to 0.2 mm and less than or equal to 2.0 mm. In the embodiment shown, the first wall section 24 is approximately 0.5 mm thick.

[0070] Regarding the surface quality of the wall 18 of the tubular plant cover 10, it should be noted at this point that the average roughness depth Rz on the inner circumferential surface 20 of the wall 18 is greater than or equal to 20 µm and less than or equal to 120 µm; in one of the tested tubular plant covers 10, namely the exemplary embodiment shown here, it was, for example, 70 µm. These surface qualities (RZ) should also be maintained in the other exemplary embodiments.

[0071] The further embodiments will be described below only insofar as they differ significantly from the above with reference to the Fig. 1 to 3 and 21 described first embodiment.

[0072] The second and third embodiments according to the Fig. 4 to Fig. 6 or 7 to 12 is initially common that - as best seen in the Fig. 6 and Fig. 11 - the wall 118, 218 surrounding the cavity 122, 222 comprises first and second wall sections 124, 126, 224, 226 of different wall thickness T1, T2, which alternate along the longitudinal axis 116, 216 between the openings 112, 114, 212, 214 and in a radial direction relative to the longitudinal axis 116, 216, as seen in section. The smaller wall thickness T1 of the wall 118, 218 provides the above-mentioned target decomposition points (not shown here), at which breakthroughs (also not shown) first occur in the wall 118, 218 during the degradation of the plant cover 110, 210, while the larger wall thickness T2 of the wall 118, 218 stiffens the plant cover 110, 210, analogously to the first embodiment.

[0073] More precisely, the wall 118, 218 of the tubular plant cover 110, 210 according to the second embodiment, as well as according to the third embodiment, is configured such that the wall 118, 218, viewed in a longitudinal section, has a substantially rectangular wave-shaped contour 136, 236, which, in a second manufacturing variant, is formed from a tubular base body using a blow molding process. Here, radially inner and radially outer second wall sections 126, 226 of greater wall thickness T2 are formed with respect to and substantially parallel to the longitudinal axis 116, 216, which have a length L2 (radially outer) and L2' (radially inner), respectively. The second wall sections 126, 226 are connected to one another via first wall sections 124, 224 of smaller wall thickness T1, which extend with a height H1 in a substantially radial direction with respect to the longitudinal axis 116, 226.

[0074] The different wall thicknesses T1, T2 on the walls 118, 218 are created in these two embodiments during blow molding, either in individual blow molds or in rotating blow molds using the corrugator process, as already described above. Accordingly, the radially outer second wall sections 126, 226—which are somewhat longer (length L2) in these embodiments—are pushed outward and displaced by internal pressure on the wall 118, 218 relative to the radially inner second wall sections 126, 226—which are held in the respective blow mold by contact—and are somewhat shorter (length L2') in the embodiments. The wall thickness T2 of these second wall sections 126, 226 remains essentially the same, stiffening the structure of the tubular plant cover 110, 210.At the same time, the first wall sections 124, 224 connecting the second wall sections 126, 226 to one another stretch to the height H1, with expansion of the base material in a direction substantially radial to the longitudinal axis 116, 216. With increasing radial expansion of the first wall sections 124, 224, their wall thickness T1 decreases, and the first wall sections 124, 224 therefore taper accordingly, as shown in FIGS. Fig. 6 and Fig. 11. This creates the aforementioned decomposition sites at these locations, where the perforations in the wall 118, 218 first occur during the biodegradation of the tubular plant cover 110, 210.

[0075] In light of the tests carried out with the above-mentioned materials, it appears expedient to select the relative dimensions of the tubular plant covers 110, 210 according to the second and third embodiments such that the ratio of the height H1 of the first wall sections 124, 224 with smaller wall thickness T1 in the direction transverse to the longitudinal axis 116, 216 to the length L2 of the second wall sections 126, 226 with greater wall thickness T2 in the direction of the longitudinal axis 116, 216 is between 1 / 2 and 2 / 1. Fig. For the tubular plant covers 110, 210 shown in Figures 4 to 12, this ratio is specifically 1: 1.125.

[0076] As far as the relative wall thicknesses are concerned, the tubular plant covers 110, 210 shown here are dimensioned such that the ratio of the smaller wall thickness T1 of the first wall sections 124, 224 of the wall 118, 218 to the average diameter D (see Fig. 6 or 10) of the inner circumferential surface 120, 220 of the wall 118, 218 is specifically approximately 1:208, i.e., in the above-mentioned range from 1:250 to 1:25. Finally, in these exemplary embodiments, the ratio of the smaller wall thickness T1 of the first wall section 124, 224 to the larger wall thickness T2 of the second wall section 126, 226 is specifically 1:2, i.e., also in the above-mentioned range from 1:1.1 to 1:3.0. The following also applies here: Ultimately, these dimensions also depend on which biodegradable material is used for the wall 118, 218, as well as on the detailed design of the respective blow molding process.

[0077] With regard to the absolute dimensions, it can finally be noted for the tubular plant covers 110, 210 according to the second and third embodiments that the smaller wall thickness T1 of the first wall section 124, 224 of the wall 118, 218 here is approximately 0.25 mm, accordingly lying in the range between 0.2 mm and 2.0 mm already mentioned above.

[0078] A special feature of the third embodiment according to the Fig. 7 to 12 compared to the second embodiment according to the Fig. 4 to 6 is that at least two - here four - ribs 238 are formed on the wall 218, projecting radially inwards in the direction of the longitudinal axis 216 and extending essentially parallel to the longitudinal axis 216 (best in the Fig. 7, Fig. 10 and Fig. 12). These ribs 238 serve as root orientation aids for the vital main root of the young plant to be formed in the cavity 222 of the tubular plant cover 210. The ribs 238 can be formed in the biodegradable material of the wall 218 after its formation as a hollow body, e.g., by means of a hot stamping process, which is also possible in principle in all other embodiments.

[0079] In the blow-molded third embodiment, however, it is advantageous with regard to the highest possible efficiency in production if the ribs 238 are formed together with the substantially rectangular wave-shaped contour 236 of the wall 218 from the tubular base body by means of the blow molding process. As can be seen from the detailed illustration according to Fig. 12, the wall thickness of the ribs 238 expands radially outwardly, viewed in section, over a corner against which the wall 218 initially rests in the blow mold. At these corners, where the roots forming in the tubular planting sleeve 210 are redirected from circumferential growth to longitudinal growth along the ribs 238, a further thin-walled region is thus created with the aforementioned target decomposition sites, where the perforations in the wall 218 first form during the biodegradation of the tubular planting sleeve 210.

[0080] The one in the Fig. 13 to 20, is that the wall 318, 418 comprises first and second wall sections 324, 326, 424, 426 of different wall thicknesses T1, T2, which alternate in a circumferential direction around the longitudinal axis 316, 416, as seen in section. Here, the smaller wall thickness T1 of the wall 318, 418 again creates predetermined decomposition points (not shown), at which breakthroughs (also not shown) first occur in the wall 318, 418 during the biodegradation of the plant cover 310, 410. At the same time, the greater wall thickness T2 of the wall 318, 418 stiffens the plant cover 310, 410.

[0081] More precisely, in a third manufacturing variant of the tubular plant cover 310, 410, the wall 318, 418 is rolled around the longitudinal axis 316, 416 from at least one sheet of biodegradable material to form a substantially cylindrical cavity 322 delimited by the inner circumferential surface 320, 420 and open at the openings 312, 314, 412, 414 in the case of the fourth embodiment or a substantially frustoconical cavity 422 in the case of the fifth embodiment. In this case, overlapping, interconnected curved edge regions 340, 341, 440, 441 form at least one second wall section 326, 426 of greater wall thickness T2, to which at least one first wall section 324, 424 of smaller wall thickness T1 adjoins in the circumferential direction around the longitudinal axis 316, 416.

[0082] How best to Fig. 16 and Fig. 20, in the area of ​​the overlap 330, 430 of the interconnected sheet edge regions 340, 341, 440, 441 with respect to the longitudinal axis 316, 416, an outer side 332, 432 of the sheet is welded or glued to an inner side 334, 434 of the sheet.

[0083] Regarding the relative and absolute dimensions of the tubular plant covers 310, 410 according to the fourth and fifth embodiments, reference can first be made to the preferred ranges already indicated above for the other embodiments with regard to the materials examined. Fig. 13 to 16 and 17 to 20, the ratio of the smaller wall thickness T1 of the first wall sections 324, 424 of the wall 318, 418 to the average diameter D (see the Fig. 13, Fig. 16 or 17, Fig. 20) of the inner circumferential surface 320, 420 of the wall 318, 418 is specifically approximately 1:125 (fourth embodiment) or 1:105 (fifth embodiment). Finally, in these embodiments, the ratio of the smaller wall thickness T1 of the first wall section 324, 424 to the larger wall thickness T2 of the second wall section 326, 426 is specifically approximately 1:2 due to the doubling of material at the overlap 330, 430, with the larger wall thickness T2 in the area of ​​the overlap 330, 430 being somewhat smaller during welding and somewhat larger during gluing. The smaller wall thickness T1 in the illustrated embodiments is absolutely 0.4 mm, with an average diameter of approximately 50 mm for the cylindrical tubular plant cover 310 and approximately 42 mm for the conical tubular plant cover 410.

[0084] In the Fig. Finally, the fourth and fifth embodiments shown in Figures 13 to 20 each represent—also for the sake of simplicity—the simplest design with only one sheet of biodegradable material wound around the longitudinal axis 316, 416. It will be apparent to those skilled in the art that, if necessary, the use of multiple sheets connected to one another in an overlapping manner at the respective sheet edge regions can advantageously be used to variably adjust the rigidity and also produce various special sizes of the tubular plant cover 310, 410.

[0085] The Fig. 22 to 24 finally show a sixth embodiment of the tubular plant cover 510 in a basic form ( Fig. 22) and two variants ( Fig. 23 and Fig. 24). A special feature of the sixth exemplary embodiment compared to the previously described first to fifth exemplary embodiments is that the wall 518 comprises first and second wall sections 524, 526 made of different materials, namely materials that biodegrade at different rates, which alternate along the longitudinal axis 516 between the openings (not shown here) of the tubular plant cover 510 and in a radial direction relative to the longitudinal axis 516, as seen in section. The more rapidly biodegradable material of the first wall section 524 provides the desired decomposition points (not shown) of the wall 518, at which the openings (also not shown) first form in the wall 518 during the biodegradation of the plant cover 510, while the more slowly biodegradable material of the second wall section 526 of the wall 518 stiffens the plant cover 510.

[0086] Specifically, in the sixth exemplary embodiment in its various variants, the wall 518 surrounding the cavity 522 of the tubular plant cover 510 and delimiting the cavity 522 with its inner circumferential surface 520 is formed by a profile 528 coextruded from the various materials with a profile width B, which is wound helically around the longitudinal axis 516 and overlaps at longitudinal edges that are essentially wedge-shaped (wedge angle α) when viewed in cross-section, analogously to the first exemplary embodiment. The second wall section 526 made of the more slowly biodegradable material is embedded in the first wall section 524 made of the more rapidly biodegradable material. In this embodiment, too, in the region of the overlap 530 with respect to the longitudinal axis 516, an outer side 532 of the band-like profile 528 is integrally welded or glued to an inner side 534 of the profile 528, likewise corresponding to the first embodiment.

[0087] The Fig. 22 to 24 finally also illustrate how, by specific shaping and dimensioning of the second wall section 526 - elliptical in cross section with a major axis length d1 and a minor axis length d2 according to Fig. 22 or round with a diameter d according to the Fig. 23 and Fig. 24 - as well as the axial and radial position of the second wall section 526 within the first wall section 524 in the profile 528 with respect to the longitudinal axis 516, in a simple manner - namely by suitable design of the nozzle for coextrusion of the profile 528 - not only the mechanical strength of the second wall section 526 and thus of the tubular plant cover 510 as a whole, but also the effective thickness t of the first wall section 524 and thus indirectly also the decomposition behavior of the tubular plant cover 510 can be influenced according to the respective requirements.

[0088] A tubular planting sleeve for pre-cultivation and planting of forest and fruit trees has an opening at each opposite end and, in between along a longitudinal axis, a wall made of biodegradable material, which, with an inner circumferential surface, defines a cavity for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the planting sleeve. The wall comprises first and second wall sections a) of different wall thicknesses, which alternate along the longitudinal axis between the openings and / or in a direction radial to the longitudinal axis and / or in a circumferential direction around the longitudinal axis, as seen in section, or b) made of different materials that biodegrade at different rates.The smaller wall thickness - or the faster biodegradable material - ensures target decomposition points where wall breakthroughs first occur during the biodegradation of the plant cover, while the larger wall thickness - or the slower biodegradable material - stiffens the plant cover. LIST OF REFERENCE SYMBOLS 10 plant covers 12 Opening 14 Opening 16 Longitudinal axis 18 wall 20 inner circumferential surface 22 Cavity 24 first wall section 25 target decomposition sites 26 second wall section 28 band or profile 30 Overlap 32 Outside 34 Inside 35 breakthroughs 110 Plant cover 112 Opening 114 Opening 116 Longitudinal axis 118 wall 120 inner circumferential surface 122 cavity 124 first wall section 126 second wall section 136 rectangular wave contour 210 Plant cover 212 Opening 214 Opening 216 Longitudinal axis 218 wall 220 inner circumferential surface 222 Cavity 224 first wall section 226 second wall section 236 rectangular wave contour 238 Rib 310 Plant cover 312 Opening 314 Opening 316 Longitudinal axis 318 wall 320 inner circumferential surface 322 cavity 324 first wall section 326 second wall section 330 Overlap 332 Outside 334 Inside 340 sheet edge area 341 Sheet edge area 410 Plant cover 412 Opening 414 Opening 416 Longitudinal axis 418 wall 420 inner circumferential surface 422 Cavity 424 first wall section 426 second wall section 430 Overlap 432 Outside 434 Inside 440 sheet edge area 441 Sheet edge area 510 Plant Cover 516 Longitudinal axis 518 wall 520 inner circumferential surface 522 cavity 524 first wall section 526 second wall section 528 Profile 530 Overlap 532 Outside 534 Inside α wedge angle on the profile d Diameter (cross-section of 2nd wall section) d1 main axis length (cross-section of 2nd wall section) d2 minor axis length (cross-section of 2nd wall section) t effective thickness (1st wall section) B Width of the strip or profile B1 Width (1st wall section) B2 Width (2nd wall section) D Diameter of the inner peripheral surface H1 Height (1st wall section) L2 Length (2nd wall section, radially outside) L2' Length (2nd wall section, radially inside) Rz roughness depth T1 Wall thickness (1st wall section) T2 wall thickness (2nd wall section) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 36 38 312 A1

[0004] WO 2022 / 253782 A1 [0006, 0007, 0017, 0060] EP 0 097 735 A1

[0010]

Claims

[1] Tubular planting cover (10, 110, 210, 310, 410, 510) for pre-cultivation and planting of forest and fruit trees, which has an opening (12, 14; 112, 114; 212, 214; 312, 314; 412, 414) at opposite ends and in between along a longitudinal axis (16, 116, 216, 316, 416, 516) a wall (18, 118, 218, 318, 418, 518) made of biodegradable material, which has an inner peripheral surface (20, 120, 220, 320, 420, 520) a cavity (22, 122, 222, 322, 422, 522) for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the plant cover (10, 110, 210, 310, 410, 510), characterized bythat the wall (18, 118, 218, 318, 418, 518) comprises first and second wall sections (24, 26; 124, 126; 224, 226; 324, 326; 424, 426; 524, 526) made of different materials that are biodegradable at different rates, or of different wall thicknesses (T1, T2), which alternate along the longitudinal axis between the openings and / or in a radial direction relative to the longitudinal axis and / or in a circumferential direction around the longitudinal axis, seen in section, wherein the more rapidly biodegradable material or a smaller wall thickness (T1) of the wall (18, 118, 218, 318, 418, 518) provides for desired decomposition points (25) at which, during the degradation of the plant cover (10, 110, 210, 310, 410, 510) firstly openings (35) are created in the wall (18, 118, 218, 318, 418, 518), while the slower biodegradable material or a greater wall thickness (T2) of the wall (18, 118, 218, 318, 418, 518) stiffens the plant cover (10, 110, 210, 310, 410, 510). [2] Tubular plant cover (10, 510) according to claim 1, characterized by , that the wall (18) consists of a band (28) or profile of predetermined width (B) which is wound helically and partially overlapping around the longitudinal axis (16), wherein the band (28) or profile forms the second wall section (26) of greater wall thickness (T2) in the region of the overlap (30) and, adjacent thereto, the first wall section (24) of smaller wall thickness (T1), or the wall (518) is formed by a profile (528) coextruded from the different materials, which is wound around the longitudinal axis (516) in a helical manner and overlapping at longitudinal edges which, when viewed in cross-section, are essentially wedge-shaped, wherein the second wall section (526) made of the more slowly biodegradable material is embedded in the first wall section (524) made of the more quickly biodegradable material. [3] Tubular plant cover (10, 510) according to claim 2, characterized by that in the region of the overlap (30, 530) with respect to the longitudinal axis (16, 516) an outer side (32, 532) of the band (28) or profile (528) is glued or welded to an inner side (34, 534) of the band (28) or profile (528). [4] Tubular plant cover (10) according to claim 2 or 3, characterized by that the ratio of the width (B2) of the second wall section (26) running helically around the longitudinal axis (16) to the width (B1) of the first wall section (24) running helically around the longitudinal axis (16), measured in the width direction of the wound strip (28) or profile, lies in a range between 1 / 16 and 12 / 1. [5] Tubular plant cover (10) according to one of claims 2 to 4, characterized by , that the width (B1) of the first wall section (24) extending helically around the longitudinal axis (16) is between 1.5 mm and 20.0 mm, measured in the width direction of the wound strip (28) or profile, and / or that the width (B2) of the second wall section (26) running helically around the longitudinal axis (16) is between 0.5 mm and 9.0 mm, measured in the width direction of the wound strip (28) or profile. [6] Tubular plant cover (110, 210) according to claim 1, characterized byin that the wall (118, 218), seen in a longitudinal section, has a substantially rectangular wave-shaped contour (136, 236) which is formed from a tubular base body by means of a blow-molding process, so that radially inner and radially outer, second wall sections (126, 226) of greater wall thickness (T2) are formed with respect to and substantially parallel to the longitudinal axis (116, 216), which are connected to one another via first wall sections (124, 224) of smaller wall thickness (T1) which extend in a substantially radial direction with respect to the longitudinal axis (116, 226). [7] Tubular plant cover (110, 210) according to claim 6, characterized by that the ratio of the height (H1) of the first wall sections (124, 224) with smaller wall thickness (T1) in the direction transverse to the longitudinal axis (116, 216) to the length (L2, L2') of the second wall sections (126, 226) with greater wall thickness (T2) in the direction of the longitudinal axis (116, 216) is between 1 / 2 and 2 / 1. [8] Tubular plant cover (310, 410) according to claim 1, characterized by in that the wall (318, 418) is rolled from at least one sheet of biodegradable material around the longitudinal axis (316, 416) to form a substantially cylindrical cavity (322) or a substantially frustoconical cavity (422), wherein overlapping, interconnected sheet edge regions (340, 341; 440, 441) form at least one second wall section (326, 426) of greater wall thickness (T2), to which at least one first wall section (324, 424) of smaller wall thickness (T1) adjoins in the circumferential direction around the longitudinal axis (316, 416). [9] Tubular plant cover (310, 410) according to claim 8, characterized bythat in the region of the overlap (330, 430) of the interconnected sheet edge regions (340, 341; 440, 441) with respect to the longitudinal axis (316, 416), an outer side (332, 432) of the sheet is glued or welded to an inner side (334, 434) of the sheet. [10] Tubular plant cover (10, 110, 210, 310, 410) according to one of the preceding claims, characterized by , that the ratio of the smaller wall thickness (T1) of the first wall section (24, 124, 224, 324, 424) of the wall (18, 118, 218, 318, 418) to the average diameter (D) of the inner circumferential surface (20, 120, 220, 320, 420) of the wall (18, 118, 218, 318, 418) is in a range from 1:250 to 1:25 and / or that the smaller wall thickness (T1) of the first wall section (24, 124, 224, 324, 424) of the wall (18, 118, 218, 318, 418) is greater than or equal to 0.2 mm and less than or equal to 2.0 mm and / or that the ratio of the smaller wall thickness (T1) of the first wall section (24, 124, 224, 324, 424) to the larger wall thickness (T2) of the second wall section (26, 126, 226, 326, 426) is in a range from 1 : 1.1 to 1 : 3.0 and / or that the average surface roughness (Rz) on the inner circumferential surface (20, 120, 220, 320, 420, 520) of the wall (18, 118, 218, 318, 418, 518) is greater than or equal to 20 µm and less than or equal to 120 µm. [11] Tubular plant cover (210) according to one of the preceding claims, characterized by that at least two, preferably four, ribs (238) are formed on the wall (218) which project radially inwards in the direction of the longitudinal axis (216) and extend substantially parallel to the longitudinal axis (216), said ribs serving as root orientation aids for the vital main root to be formed. [12] Tubular plant cover (210) according to claim 11, characterized bythat the ribs (238) are formed in the biodegradable material of the wall (218) by means of a hot stamping process. [13] Tubular plant cover (210) according to claims 6 and 11 or 7 and 11, characterized by that the ribs (238) together with the substantially rectangular wave-shaped contour (236) of the wall (218) are formed from a tubular base body by means of a blow molding process. [14] Tubular plant cover (10, 110, 210, 310, 410, 510) according to one of the preceding claims, characterized by that the biodegradable material or materials of the wall (18, 118, 218, 318, 418, 518) are selected from a group comprising the following materials: polybutylene succinate-co-butylene adipate (PBSA); Polyhydroxyalkanoate (PHA); Cellulose acetate; natural polymers such as starch; Polylactic acid compounds (PLA compounds); Polybutylene adipate terephthalate (PBAT). [15] Use of a tubular plant cover (10, 110, 210, 310, 410, 510) according to one of the preceding claims for pre-cultivation and planting of forest and fruit trees.

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