Tubular planting sleeve and use of same for pre-cultivating and planting forestry and fruit plants

Abstract

A tubular planting sleeve (210) for forestry and fruit plants has an opening at each opposite end and therebetween, along a longitudinal axis, a wall (218) of biodegradable material, the inner circumferential surface of which delimits a hollow space which is suitable for receiving a plant germ embedded in a substrate, from which plant germ a vital main root is to form in the planting sleeve. The wall comprises first and second wall portions (224, 226) a) of different wall thicknesses, which alternate, as seen in cross-section, or b) of different materials which biodegrade at different speeds. The smaller wall thickness - or the material which biodegrades more quickly - provides predefined decomposition points at which, during biodegradation of the planting sleeve, holes first occur in the wall, while the larger wall thickness - or the material which biodegrades more slowly - reinforces the planting sleeve.

Description

[0001] Tubular plant cover and use thereof for

[0002] PRE-CULTIVATION AND PLANTING OF FORESTRY AND FRUIT TREES

[0003] TECHNICAL FIELD

[0004] The present invention relates generally to a tubular plant cover for forestry and fruit trees, which has an opening at each opposite end and a wall made of biodegradable material between them along a longitudinal axis, which wall defines a cavity with an inner circumferential surface which is suitable for receiving a plant germ embedded in a substrate, from which plant germ a vital main root is to be formed in the plant cover, wherein the wall comprises first and second wall sections, according to the preamble of patent claim 1. In particular, the invention relates to such a plant cover 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 plant cover for pre-cultivating and planting forestry and fruit trees.

[0005] BACKGROUND OF THE INVENTION AND STATE OF THE ART

[0006] Maintaining the productivity of forest areas and expanding forest areas 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 forests, the planting of drought-resistant, thermophilic, and economically valuable tree species is also important.

[0007] Currently used standard forestry planting practices utilize a one- or multi-year pre-culture in a tree nursery to produce planting material. 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 - seedling drying out and seed consumption by birds and mammals. The seed saving associated with planting is also of great importance for sessile oaks and English oaks, for example, since sufficient seed quantities for establishing a stand by seed are only available for these species in years with good fruiting.

[0008] In recent decades, pre-cultivated container plants have been increasingly used for forest stand establishment. Reusable pallets of substrate-filled, hard-walled plastic containers, such as those described in publication DE 36 38 312 A1, have proven effective for their cultivation.

[0009] 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.

[0010] In this context, a container for pre-cultivating and planting forest trees is known from the publication WO 2022 / 253782 A1, which container is formed from a pipe segment. This container is intended to provide optimal growth conditions for the plant germ until the formation of a vital main root and is to be used immediately after the pre-cultivation phase for planting the plants in the open, 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 at the time of planting.

[0011] More precisely, the vessel disclosed in the document WO 2022 / 253782 A1 is made of a biodegradable, preferably isodiametric pipe segment that is open on both sides, has a stable wall that is 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 that has a proportion of water-binding particles of more than 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.

[0012] 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 outside 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 outside of the hard paper wall.With this type of design of the pipe segment, the cylindrical shipping sleeve made of hard paper ensures that the pipe segment is sufficiently stable during pre-cultivation, while the film tube section protects the shipping sleeve made of hard paper against water penetration and seals the wall of the pipe segment from the inside and outside. Even though this type of design of the pipe segment appears to be entirely suitable for research and testing purposes, it does entail certain risks if the pipe segment is to be used on an industrial scale, for example in the semi-automated cultivation of large quantities of young plants. If the enclosing film tube section is damaged during filling or transport of the pipe segment, there is a risk that the shipping sleeve made of hard paper will absorb water and subsequently soften, possibly even before it has been planned.even collapsed, i.e. is no longer sufficiently mechanically strong or rigid. Upright transport and / or mechanical planting of the young plant in the pipe segment would then no longer be possible. A similar problem can be expected if the pipe segment is accidentally filled and put down 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 via the collar formed by the outer end of the film tube section and soften the hard paper shipping sleeve.

[0013] Similar containers and the problems associated with them are also known from the 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 provided with a filling of soil, peat or a substrate that enables and / or promotes growth, 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 latter 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.

[0014] Since with this state of the art it is not possible to control when and where the walls of the individual planting stumps dissolve, it is further proposed that a layer, 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 neighbouring planting stumps from becoming matted 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, where the layer, intermediate layer or similar...Since removing them requires 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 period and are no longer suitable for retaining water. Furthermore, the rather mushy or doughy consistency of the individual, already partially decomposed planting stumps makes them difficult to handle during transport and planting.

[0015] Furthermore, from the document DE 10 2022 113 773 A1, which forms the preamble of patent claim 1, a tubular root protection sleeve for forest trees is known, which has an opening at each opposite end and a wall made of biodegradable material in between along a longitudinal axis. The wall delimits a cavity with an inner circumferential surface, which is suitable for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the sleeve. More precisely, this sleeve has a substantially circular, oval, rectangular, square or polygonal cross-section and has a tubular structure and a length of more than 5 cm. The wall thickness of the sleeve is in a range between 0.3 mm and 5 mm, preferably in the range from 1 mm to 3 mm. The material of the sleeve consists of a home or.Earth-degradable plastic which contains a predetermined proportion of natural fibres, preferably sunflower shell fibres, wherein this proportion of natural fibres in the total proportion is preferably higher than 10%, e.g. 10% to 70%.

[0016] In this state of the art, the wall can comprise first and second wall sections. Thus, in one variant, the root protection casing can have uneven wall thicknesses along its length and / or circumference. This can be achieved, for example, by - in the words of this publication - "the root protection casing is developed from a wall material which is wound up into a root protection casing, whereby in the overlapping area, i.e. where the superimposed strips touch (and can be connected to one another in a known manner, e.g. glued), the wall thickness is twice that of the area where no such overlap occurs."

[0017] Furthermore, from the publication AT 523044 A4, a plant protection cover is known which comprises at least one layer of cardboard and, on its outer side, at least one layer of bioplastic. The cardboard layer can be a helically wound strip of cardboard, with openings being provided between the individual turns of the cardboard strip, which are covered by the layer of bioplastic arranged at least on the outer side of the protective cover. The bioplastic should be translucent or transparent so that the plant to be protected can be supplied with sufficient light through the openings.

[0018] This is therefore a protective covering designed to protect the above-ground part of a plant. The cardboard spiral, which generally decomposes more quickly, serves to stiffen the protective covering, while the bioplastic is intended to protect it from the elements: "The bioplastic, which is provided particularly on the outside of the cardboard, protects the cardboard from the elements. As a result, the protective covering is well-resistant to the weather and does not dissolve in rain, etc. " However, the plant protection covering known from this state of the art is neither intended nor suitable for use as a protective covering in the root area of ​​a plant.

[0019] In addition, the document DE 10 2009 003 164 A1 shows a plant sleeve, in particular for protecting cultivated plants during the growth phase, with a wall made of at least one wall material and a lumen, wherein it is intended to have biostatic and / or biocidal properties due to its physical properties and / or its chemical composition.

[0020] Finally, WO 2013 / 019105 A2 discloses a plant tray for propagating plants, comprising a plurality of cups for receiving a plant growth medium and a seed, a cutting, and / or a plant that is at least partially embedded in the plant growth medium. Each cup has a bottom structure that is penetrable by a downwardly growing plant root. Furthermore, the tray comprises spacers that extend downward beyond the bottom structure of the cups and are intended to prevent the cups with their bottom structure from standing on established soil. OBJECTIVE

[0021] Compared to the described prior art, the object of the invention is to create an alternative tubular plant cover for forestry and fruit trees that can be mass-produced as cost-effectively as possible and with comparatively low material expenditure, which generally also addresses the disadvantages of the prior art described above and specifically has a wall that is sufficiently stable for a standing pre-culture, subsequent standing transport and 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 type, degree of pre-cultivation), climate and soil conditions at the location of use.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 held in the tubular plant cover.

[0022] PRESENTATION OF THE INVENTION

[0023] 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.

[0024] In a tubular plant cover for forestry and fruit trees, which has an opening at each of the opposite ends and a wall made of biodegradable material therebetween along a longitudinal axis, which wall defines a cavity with an inner circumferential surface which is suitable for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the plant cover, wherein the wall comprises first and second wall sections;According to the invention, the first and second wall sections consist of different materials which biodegrade at different rates (hereinafter also referred to as the first structural alternative), or the wall is formed from second wall sections which are radially inner and radially outer with respect to the longitudinal axis and have a greater wall thickness and extend essentially parallel to the longitudinal axis, as well as first wall sections which have a smaller wall thickness and extend essentially radially with respect to the longitudinal axis and connect the second wall sections to one another (second structural alternative), the more rapidly biodegradable material or the smaller wall thickness of the wall providing target decomposition points at which breakthroughs in the wall first occur during the degradation of the plant cover, while the more slowly biodegradable material or the greater wall thickness of the wall stiffens the plant cover.

[0025] 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. The tubular plant cover according to the invention is generally suitable for growing seedlings from smaller seeds, such as e.g.Apple seeds, from larger seeds, such as acorns, beechnuts, or chestnuts, as well as from sprouts and seedlings. Furthermore, the tubular planting sleeve according to the invention is also fundamentally adaptable and suitable for growing seedlings from "cuttings," which are therefore also intended to be included in the term "plant germ." Cuttings are, by definition, parts of plant shoots that are cut off for the purpose of vegetative propagation and inserted into a culture substrate filled into the tubular planting sleeve to develop their own roots. The tubular planting sleeve according to the invention can therefore advantageously be used in a variety of ways for the pre-cultivation and planting of forest and fruit trees.

[0026] With regard to the "substrate", i.e. the filling of the tubular plant 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 document WO 2022 / 253782 A1 discussed at the beginning, since the present invention is primarily concerned with the structure and function of the tubular plant casing as such.

[0027] 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 has the function of stiffening the wall. In the context of the present invention, "desired decomposition sites" in / on the first wall section are to be understood as wall regions 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.

[0028] The second wall section of the tubular planting casing, on the other hand, is advantageously designed to be mechanically stable, strong and rigid such that the tubular planting casing has a sufficiently stable wall, whereby upright pre-cultivation, upright transport, even after pre-cultivation, and / or mechanical spreading of the young plant in the tubular planting casing into the planting soil is possible without any problems. In this case, it is consciously accepted that the planting casing 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 longer or are detectable than parts of the first wall section.

[0029] 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 occurs predominantly perpendicular to the thickness direction of the first wall section, both from the inside outwards and from the outside inwards in relation to the wall. The breakthroughs in the wall that first occur at the desired decomposition points of the first wall section then mean that the decomposition attack on the wall also occurs in the surface extension directions of the first wall sections with decomposition attack components in further directions with regard 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".

[0030] Because the first wall section and the second wall section alternate in cross-section, a defined distribution of the desired decomposition points on the wall is advantageously achieved. This results in a better controllable, possibly more uniform and more efficient decomposition attack on the wall of the tubular plant cover, compared to a plant cover with a homogenously formed wall. This is particularly beneficial for a good adjustability of the decomposition behavior of the tubular plant cover, according to the respective application specifications and conditions (plant species, degree of pre-cultivation, climate, soil conditions at the application site, etc.).

[0031] Depending on the type of plant that is to be grown in the tubular plant cover and / or the environmental conditions that are to be expected at the later location, it may also be advantageous if small openings are made 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.

[0032] The perforations in the wall of the tubular planting sleeve promote better root growth of the respective plant during its pre-culture in two ways: Firstly, the perforations encourage good permeability and aeration of the substrate in the tubular planting sleeve, so that growth-promoting bacteria can provide more nutrients for the plant. Secondly, the perforations significantly improve root quality. More precisely, the seedling first forms a taproot, which grows downwards towards the open end of the tubular planting sleeve and comes into contact with the ambient air upon exiting the tubular planting sleeve. This then results in a so-called "air pruning", in which the end of the taproot exposed to the air dehydrates, stopping vertical root growth of the taproot and encouraging branching of the taproot towards the seedling.When the new branches branching out from the taproot to the sides encounter the perforated wall, the branches are again stopped in the particularly well-ventilated areas and stimulated to form further sub-branches. This process is repeated with each new root that finds its way to a perforation, so that the plant quickly develops a vital root structure with a mass of outward-directed, or downward-directed, fibrous roots with many additional root tips.

[0033] 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, at this stage, the lower opening of the tubular planting sleeve and the openings in the wall are covered with soil, the fine root tips can pass through the lower opening and the increasingly widening openings directly toward the surrounding soil.

[0034] Thus, the tubular plant covering according to the invention can also be advantageously optimized with regard to the formation of a root structure that is as vital as possible from a plant germ by means of an appropriate structural design of the first and second wall sections. In order to achieve the functions of the two wall sections discussed above, two structural alternatives are provided according to the invention: In the second structural alternative of the invention, the wall has alternating first and second wall sections which have different wall thicknesses. Due to the smaller wall thickness of the first wall section, the breakthroughs occur first at the intended decomposition points without endangering the mechanical stability of the tubular plant covering.In the first structural alternative of the invention, however, alternating first and second wall sections made of different materials are provided, which are biodegradable at different rates, whereby the previously described effect can also be achieved.

[0035] Because in the second structural alternative of the invention the wall is formed by the second wall sections of greater wall thickness, which extend - radially inward and radially outward with respect to the longitudinal axis - substantially parallel to the longitudinal axis, and the first wall sections of smaller wall thickness, which extend in a substantially radial direction with respect to the longitudinal axis and connect the second wall sections to one another, the first wall sections are essentially horizontal in the functional or installed position of the tubular plant cover, while the second wall sections are essentially vertical. This creates horizontal planes in the tubular plant cover on which water can collect. On the one hand, this promotes the function of the tubular plant cover as a water reservoir.On the other hand, this promotes decomposition of the biodegradable material of the first wall section. Furthermore, due to the stepped design of the wall, the filling, i.e., the substrate and plant germ, is advantageously secured against slipping out during transport and handling of the tubular plant cover during planting.

[0036] The two structural alternatives mentioned above can be realized cost-effectively and with a comparatively low material expenditure, so that a tubular plant cover predestined for mass production for the pre-cultivation and planting of forest and fruit trees is created.

[0037] The above-mentioned first structural alternative of the invention, according to which a rather rapidly biodegradable material is combined with a rather slowly biodegradable material in the tubular plant cover, is particularly suitable when, for example, the desired mechanical properties cannot be achieved with a material that is preferred with regard to decomposition behavior due to wall sections of different wall thicknesses.

[0038] In this first structural alternative, the wall is preferably formed by a profile co-extruded from the various materials, which is wound helically and overlappingly at longitudinal edges which, viewed in cross-section, are essentially wedge-shaped around the longitudinal axis of the tubular plant cover, 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 quickly biodegradable material. In another, likewise conceivable embodiment of this first 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 can be glued or welded to it.This means that both wall sections are located at a point on the wall that is exposed to direct decomposition when the tubular plant cover is in the ground.

[0039] A tubular plant cover wall wound in this way advantageously exhibits high flexural and torsional rigidity while remaining 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 tubular plant cover wall and its decomposition rate can also be easily and effectively adjusted by varying the profile cross-sectional geometry and the profile wall thickness.

[0040] 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 profile is glued or welded to an inner side of the profile. One advantage of such a material-to-material connection is its potential tightness, 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. using the residual heat of the extrudate during winding - bonding, in which a biodegradable adhesive is introduced into the area of ​​the overlap during winding, offers an alternative to welding that is easily implementable on an industrial scale.Designs are also conceivable in which the cohesion of the wall is achieved by means of adhesion or a form fit, whether in a "macrogeometric" sense - e.g. by steps in the wall material created by a fixed angle of the profile, by an additional component such as a thread when sewing, etc. - or in a "microgeometric" sense - for example by mechanical clamping or "velcro" in the area of ​​the overlap if the surface of the wall material is sufficiently rough.

[0041] A further manufacturing process is suitable for forming the above-mentioned second structural alternative of the invention, in which the wall has first and second wall sections which have different wall thicknesses. For example, for a tubular plant cover which can advantageously be produced particularly quickly on an industrial scale, the wall of the tubular plant cover can, seen in a longitudinal section, have a substantially rectangular wave-shaped contour which is formed by means of a blow molding process from a tubular base body which produces the radially inner and radially outer second wall sections of greater wall thickness with respect to and substantially parallel to the longitudinal axis, which second wall sections are connected to one another via the first wall sections of smaller wall thickness which extend in a direction substantially radial with respect to the longitudinal axis.

[0042] 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 the same 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 and is pressurized from the inside by means of a gas, e.g. air, so that the preform or the extrudate expands under the pressure, comes into contact with the negative contour of the tool and thereby reproduces or molds this. After solidification, the tool can be divided and the tubular plant cover removed.

[0043] Having said that, in general terms, blow molding is a prerequisite for the production of tubular plant covers, various process variants can be used in terms of effort and throughput. In the process variant, which is simpler in terms of equipment and thus 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 obtain the tubular shape of the plant cover.

[0044] In the more complex process variant in terms of equipment, 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 casings. This latter process variant is particularly ideal 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 casings.

[0045] 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 covering - can be achieved by suitable selection of the wall thickness of the base material and the geometry of the negative contour of the tool, from which defined expansion of the base material results during blow molding. While in blow molding the radially outer second wall sections are pressed and displaced outwards - and this with a wall thickness that remains essentially the same compared to the radially inner second wall sections - the first wall sections connecting the second wall sections to one another stretch with expansion of the base material in a direction that is essentially radial with respect 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 the desired decomposition points of the tubular plant cover, at which the openings in the wall first occur according to the invention.

[0046] Last but not least, these blow molding processes offer the advantage that the inner surface of the bias-formed tubular plant cover has a certain roughness due to the manufacturing process, which, in addition to the macrogeometric profiling of the wall, also leads to a microgeometric "interlocking" between the filled substrate and the wall when the tubular plant cover is in use.

[0047] In concrete, expedient embodiments of the blow molding process variants, for example for tubular plant covers with an outer diameter of approx. 50 mm, it can be provided that the ratio of the height of the first wall sections with smaller wall thickness in the direction transverse to the longitudinal axis to the length of the second wall sections with greater wall thickness in the direction of the longitudinal axis is between 1 / 2 and 2 / 1. The basic rule is: the higher the first wall sections with smaller wall thickness in the direction transverse to the longitudinal axis and / or the shorter the second wall sections with greater wall thickness in the direction of the longitudinal axis, the faster the tubular plant cover decomposes. On the other hand, the lower the first wall sections with smaller wall thickness in the direction transverse to the longitudinal axis and / or the longer the second wall sections with greater wall thickness in the direction of the longitudinal axis, the more stable the tubular plant cover is.Depending on the application (plant species, degree of pre-cultivation), climate and soil conditions of the site, a suitable compromise must be found for the tubular plant cover to be mass-produced.

[0048] From tests with tubular plant covers with an outer diameter of approximately 50 mm, which are particularly suitable for afforestation, the following absolute and relative design rules have proven to be practical and appropriate, and apply equally to all blow-molding process variants of the tubular plant cover according to the second structural alternative:

[0049] 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 circumferential surface of the wall should preferably be in a range from 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.

[0050] 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 from 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 pipe cross-section relevant for buckling can also be adjusted within this framework.

[0051] For all exemplary embodiments, the wall surfaces of the tubular plant cover can, in principle, be smooth, as far as technically feasible. 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 roughness of the surface, water can also adhere better to / on the wall of the tubular plant cover, which advantageously promotes decomposition of the biodegradable material of the wall.

[0052] 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 designed 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.

[0053] 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 given its tubular shape, whether by winding or blow molding. In the bias-formed, tubular plant cover, such ribs can also be formed together with the essentially rectangular wave-shaped contour of the wall in a particularly simple and rapid manner from a tubular base body by means of blow molding. The position and geometry of the ribs can be designed virtually freely; even undercuts can be realized in this way.

[0054] 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 ​​use, 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 for the wall of the tubular plant cover should be selected so that the plant cover has sufficient robustness from the time the sphagnum is filled in until it is introduced into the (forest) soil.At the same time, the plant cover should have the lowest possible weight with regard to the costs incurred during production and transport. In particular with regard to the lowest possible production costs, the lowest possible material use in production, relatively low material costs and good availability of the material on the market are desirable. From a sustainability perspective, it also makes sense to set the proportion of bio-based components as high as possible, since 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 easy to process in the respective process for producing the plant covers.

[0055] When choosing the biodegradable material for the wall, it is important to find a compromise that meets a variety of requirements as well as possible. The tests carried out 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 S.A., France, if the above-mentioned compromise which meets the various requirements as well as possible can be found with these materials.

[0056] In this context, the term "PHA" should be understood to mean materials made from the following building blocks: polyhydroxybutyrate (PHB, often abbreviated to P3HB) as 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 larger processing window;Poly3_-hydroxybutyrate-co-hydroxybutyrate (P3HB-4HB), whose two hydroxybutyrate building blocks differ in where on the respective molecule the linking takes place, 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.

[0057] Finally, it may be desirable under certain circumstances to be able to influence the degradation behaviour of the tubular plant casing by adding lime or potassium bicarbonate. In this context, tests were carried out with tubular plant casings made from different materials. Plant casings whose walls were made from certain thermoplastic compounds decomposed considerably more slowly under the influence of moist white peat or sphagnum substrates without the neutralising addition of lime or potassium bicarbonate than with the aforementioned additives (e.g. with PBSA). For example, plant casings made from 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 of importance for the introduction of the tubular plant casings in practice.For example, the decomposition of the planting casings can be inhibited by a low pH during planting production and activated after planting by raising the pH. 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.

[0058] On the other hand, plant covers 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 the biodegradation of plant covers during the seedling production phase and their subsequent activation. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] 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 according to the invention, the reference numerals are assigned to the respective embodiment by their first digit ("1" for the second embodiment, "2" for the third embodiment, and "5" for the fourth embodiment), while the second and third digits denote identical or corresponding parts or sections with the same numbers as in the first embodiment not according to the invention. In the drawings:

[0060] Fig. 1 is a side view of a tubular plant cover according to a first embodiment not according to 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;

[0061] Fig. 2 is a (longitudinal) sectional view of the tubular plant cover according to the first embodiment shown in Fig. 1 along the section line II-II in Fig. 1;

[0062] Fig. 3 is an enlarged scale view of detail III in Fig. 2, which particularly better illustrates the different wall thicknesses of the wall sections;

[0063] Fig. 4 is 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;

[0064] Fig. 5 is a (longitudinal) sectional view of the tubular plant cover according to the second embodiment shown in Fig. 4 along the section line VV in Fig. 4, to illustrate the substantially rectangular wave-shaped contour of the wall in section;

[0065] Fig. 6 is an enlarged scale view of detail VI in Fig. 5, illustrating 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;

[0066] Fig. 7 is 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 is formed from a tubular base body by means of a blow molding process in accordance with the second embodiment according to Figs. 4 to 6, so that the wall not only has first and second wall sections of different wall thicknesses, but can also have four ribs which project radially inwards in the direction of the longitudinal axis and extend essentially parallel to the longitudinal axis and serve as root orientation aids;

[0067] Fig. 8 is a side view of the tubular plant cover according to the third embodiment shown in Fig. 7; Fig. 9 is a (longitudinal) sectional view of the tubular plant cover according to the third embodiment shown in Fig. 7 along the section line IX-IX in Fig. 8;

[0068] Fig. 10 is a (transverse) sectional view of the tubular plant cover according to the third embodiment shown in Fig. 7 along the section line XX in Fig. 8;

[0069] Fig. 11 an enlarged view of the detail

[0070] XI in Fig. 9, for a better illustration of the different wall thicknesses of the wall sections;

[0071] Fig. 12 an enlarged view of the detail

[0072] XII in Fig. 10, illustrating details of a subsequently stamped rib;

[0073] Fig. 13 is a side view, broken up and down, of the tubular plant cover according to the first embodiment shown in Figs. 1 to 3, not according to the invention, which is shown in an upright position according to its intended use, for visualizing 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;

[0074] Fig. 14 is a (longitudinal) sectional view, broken off to the sides and downwards, of a tubular plant cover according to a fourth embodiment of the invention, with a wall which has first and second wall sections made of different materials which are biodegradable at different rates;

[0075] Fig. 15 is a longitudinal sectional view, broken off to the sides and downwards, of a tubular plant cover according to a first variant of the fourth embodiment according to the invention as shown in Fig. 14; and

[0076] Fig. 16 is a (longitudinal) sectional view, broken off to the sides and downwards, of a tubular plant cover according to a second variant of the fourth embodiment according to the invention as shown in Fig. 14.

[0077] 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.

[0078] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0079] In Figs. 1 to 3 and 21, a tubular planting cover for pre-cultivating and planting forest and fruit trees according to a first embodiment is generally designated by reference numeral 10; according to the above note, the tubular planting cover is provided with reference numerals 110 (second embodiment), 210 (third embodiment), and 510 (fourth embodiment) in other embodiments shown in the further figures.

[0080] The tubular plant cover 10 has an opening 12, 14 at each of its opposite ends and, in between along a longitudinal axis 16, a wall 18 made of biodegradable material. The wall 18, with an inner circumferential surface 20, defines a cavity 22 for receiving a plant germ embedded in a substrate - both of which are not shown in the figures, but have already been described in more detail at the beginning, also with reference to the prior art according to the document WO 2022 / 253782 A1, to which express reference is made again at this point - wherein a vital main root (likewise 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-cultivating and planting forestry and fruit trees can also be found in the cited prior art.

[0081] As can best be seen in the detail according to Fig. 3, the wall 18 comprises first and second wall sections 24, 26 of different wall thicknesses T1, T2, which in this exemplary embodiment alternate in section along the longitudinal axis 16 between the openings 12, 14. The smaller wall thickness T1 of the wall 18 ensures intended decomposition points 25 - see Fig. 13, which shows a section of the tubular plant casing 10 broken off at the top and bottom in its vertical functional position - at which openings 35 first form in the wall 18 during the biodegradation of the plant casing 10. These openings 35 not only bring about a controlled decomposition of the plant casing 10, but also promote plant growth in the plant casing 10. Appropriate decomposition points and breakthroughs have also been taken into account in the other embodiments, as will be explained in more detail below.These arise there as a result of the biodegradation of the wall of the tubular plant cover, which, however, is not specifically shown in the associated figures to simplify the illustration. These target decomposition points 25 and openings 35 can in fact be most easily and best visualized using the first exemplary embodiment, because they are particularly clearly visible in the side view according to Fig. 13. 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.

[0082] As is also best illustrated in Fig. 3, the wall 18 in the first exemplary embodiment consists of a band 28 (or profile) of predetermined width B, which in a first production variant is wound around the longitudinal axis 16 in a helical manner and partially overlapping (overlap 30). In this case, the band 28 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 TI. While the first wall section 24 of smaller wall thickness TI has a width B1, the second wall section 26 has a width B2, as can be seen in Fig. 3.

[0083] 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 in relation to the longitudinal axis 16. For this purpose, the band 28 made of the biodegradable material is drawn off diagonally from a nozzle of an extruder by means of a rotating mandrel (device details not shown in the figures), wherein 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 in such a way that it is welded in the areas of the overlap 30 due to the residual heat of the material without any additional energy supply from the outside. As an alternative to this, bonding with a suitable adhesive is of course also possible at this point.

[0084] In this way, an endless production of the wall 18 is possible; the finished tubular plant covers 10 are then obtained by cutting the solidified (endless) 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 which runs helically or spirally around the longitudinal axis 16 and a second wall section 26 which also runs in the form of a cylindrical spiral around the longitudinal axis 16, the width B1 of the first wall section 24 plus twice the width B2 of the second wall section 26 corresponding to the total width B of the band 28.

[0085] 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 extending helically around the longitudinal axis 16 to the width B1 of the first wall section 24 extending 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 exemplary embodiment, this ratio is 1 / 2.15.

[0086] 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 TI of the first wall section 24 of the wall 18 to the average diameter D (see Fig. 2) of the inner circumferential surface 20 of the wall 18 generally lies in a range from 1:250 to 1:25. In the illustrated embodiment, this ratio is 1:100.

[0087] Finally, the ratio of the different wall thicknesses to one another, i.e. the ratio of the smaller wall thickness TI of the first wall section 24 to the greater wall thickness T2 of the second wall section 26, is generally in a range from 1:1.1 to 1:3.0. In the case of the tubular plant cover 10 shown in Figs. 1 to 3 and 13, this ratio is specifically 1:2. Of course, these dimensions also depend on which biodegradable material is used for the wall 18, as well as on the manner in which the tubular plant cover 10 is manufactured. The specified ranges were determined in experiments in which the materials already explained in more detail at the beginning were tested as the biodegradable material for the wall 18 of the tubular plant covers 10.

[0088] Regarding the absolute dimensions of the tubular plant cover 10, it can be stated that the width Bl of the first wall section 24, which extends 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 extends 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 TI 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.

[0089] 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 pm and less than or equal to 120 pm; in one of the tested tubular plant covers 10, namely the exemplary embodiment shown here, it was, for example, 70 pm. These surface qualities (RZ) should also be maintained in the other exemplary embodiments. The other exemplary embodiments will be described below only insofar as they differ significantly from the first exemplary embodiment described above with reference to Figs. 1 to 3 and 13.

[0090] The second and third exemplary embodiments according to Fig. 4 to Fig. 6 and 7 to 12 have in common that - as can best be seen in Fig. 6 and 11 - the wall 118, 218 surrounding the cavity 122, 222 comprises first and second wall sections 124, 126, 224, 226 of different wall thicknesses TI, 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 when viewed in section. The smaller wall thickness TI of the wall 118, 218 ensures 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.

[0091] 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 designed such that the wall 118, 218, viewed in 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 TI, which extend with a height Hl in a substantially radial direction with respect to the longitudinal axis 116, 226.

[0092] The different wall thicknesses T1, T2 on the wall 118, 218 are produced in these two exemplary embodiments during blow molding either in individual blow molds or in rotating blow molds in the corrugator process, as already described at the beginning. Accordingly, the radially outer second wall sections 126, 226 - which are somewhat longer (length L2) in these exemplary embodiments - are pressed outwards and displaced by internal pressure on the wall 118, 218 with respect to the radially inner second wall sections 126, 226 - which are held in contact in the respective blow mold and are somewhat shorter (length L2') in the exemplary embodiments. The wall thickness T2 of these second wall sections 126, 226 remains essentially the same, stiffening the structure of the tubular plant covering 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 stretching of the base material in a direction essentially radial to the longitudinal axis 116, 216. With increasing radial stretching of the first wall sections 124, 224, their wall thickness TI decreases, and the first wall sections 124, 224 therefore taper accordingly, as can be clearly seen in Figs. 6 and 11. As a result, the aforementioned desired decomposition points are created at these locations, at which the breakthroughs in the wall 118, 218 first occur during the biodegradation of the tubular plant covering 110, 210. In other words, the height of the cross-sectional profile of the wall 118, 218 allows the thickness of the first wall sections 124, 224 and thus the decomposition behavior of the tubular plant cover 110, 210 to be easily and effectively adjusted according to the respective requirements.In light of the tests conducted 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 a 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 a greater wall thickness T2 in the direction of the longitudinal axis 116, 216 is between 1 / 2 and 2 / 1. For the tubular plant covers 110, 210 shown in Figs. 4 to 12, this ratio is specifically 1:1.125.

[0093] 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 TI 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 range of 1:250 to 1:25 already mentioned above. Finally, in these exemplary embodiments, the ratio of the smaller wall thickness TI of the first wall section 124, 224 to the larger wall thickness T2 of the second wall section 126, 226 is specifically 1:2, thus also within the range of 1:1.1 to 1:3.0 already mentioned above. Here, too, these dimensions ultimately 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.

[0094] With regard to the absolute dimensions, it can finally be noted for the tubular plant covers 110, 210 according to the second and third exemplary embodiments that the smaller wall thickness TI of the first wall section 124, 224 of the wall 118, 218 is approximately 0.25 mm here, and accordingly lies in the above-mentioned range between 0.2 mm and 2.0 mm. A special feature of the third exemplary embodiment according to Figs. 7 to 12 compared to the second exemplary embodiment according to Figs. 4 to 6 is that at least two - here four - ribs 238 are formed on the wall 218, which project radially inwards in the direction of the longitudinal axis 216 and extend essentially parallel to the longitudinal axis 216 (best seen in Figs. 7, 10 and 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, for example by means of a hot stamping process, which is illustrated in Fig. 12 and is in principle also possible in all other embodiments according to the invention.

[0095] In the bias-formed third embodiment, however, it is advantageous with regard to the highest possible efficiency in production if the ribs 238 are formed from the tubular base body by means of the blow molding process together with the substantially rectangular wave-shaped contour 236 of the wall 218.

[0096] As can be seen from the detailed illustration in Fig. 12, in a subsequently embossed rib 238, the wall thickness of the ribs 238 expands radially outwards over a corner when viewed in section. This would be the opposite with a bias-formed rib, the wall thickness of which would taper radially outwards before the rib again merges into the rest of the wall over corners. At these corners, at which the roots forming in the tubular plant casing 210 are redirected from growth in the circumferential direction to growth in the longitudinal direction along the ribs 238, a further thin-walled region is thus created with the aforementioned desired decomposition points, at which the openings in the wall 218 first form during the biodegradation of the tubular plant casing 210.

[0097] Figs. 14 to 16 finally show a fourth exemplary embodiment of the tubular plant cover 510 in a basic form (Fig. 14) and two variants thereof (Figs. 15 and 16). A special feature of the fourth exemplary embodiment in comparison to the previously described first to third 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 when viewed 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) in the wall 518 first occur 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.

[0098] Specifically, in the fourth 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 co-extruded from the different materials and having a profile width B, which is wound around the longitudinal axis 516 in a helical manner and overlaps at longitudinal edges which, viewed in cross-section, are essentially wedge-shaped (wedge angle α), similar 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 quickly biodegradable material. As an alternative to this, the two wall sections made of different materials can also lie on top of or next to one another (not shown here), without one material being completely surrounded by the other material, which can also be done, for example,by coextrusion. 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 welded or glued to an inner side 534 of the profile 528, likewise corresponding to the first embodiment.

[0099] 14 to 16 finally also illustrate how, by means of a specific shape and dimension of the second wall section 526 - elliptical in cross-section with a major axis length dl and a minor axis length d2 according to Fig. 14 or round with a diameter d according to Figs. 15 and 16 - 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, not only the mechanical strength of the second wall section 526 and thus of the tubular plant casing 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 casing 510 can be influenced in a simple manner according to the respective requirements - namely by means of a suitable design of the nozzle for coextrusion of the profile 528.

[0100] A tubular plant cover for forestry and fruit trees has an opening at each end and, in between along a longitudinal axis, a wall made of biodegradable material which, with an inner circumferential surface, defines a cavity suitable for receiving a plant germ embedded in a substrate from which a vital main root is to form in the plant cover. The wall comprises first and second wall sections a) of different wall thicknesses which alternate when viewed in section, or b) made of different materials which biodegrade at different rates. The smaller wall thickness - or the more quickly biodegradable material - creates target decomposition points at which wall breakthroughs first occur during the biodegradation of the plant cover, while the greater wall thickness - or the more slowly biodegradable material - stiffens the plant cover.

[0101] LIST OF REFERENCE SYMBOLS

[0102] Plant cover

[0103] Opening

[0104] Opening

[0105] Longitudinal axis

[0106] wall

[0107] inner circumferential surface

[0108] Cavity first wall section

[0109] Should decompose second wall section

[0110] Band or profile

[0111] overlap

[0112] outside

[0113] inside

[0114] Breakthroughs

[0115] Plant cover

[0116] Opening

[0117] Opening

[0118] Longitudinal axis

[0119] wall

[0120] inner circumferential surface

[0121] Cavity first wall section second wall section rectangular wave-shaped contour

[0122] Plant cover

[0123] Opening

[0124] Opening

[0125] Longitudinal axis

[0126] wall

[0127] Inner circumferential surface 222 cavity

[0128] 224 first wall section

[0129] 226 second wall section

[0130] 236 rectangular wave-shaped contour

[0131] 238 Rib

[0132] 510 Plant cover

[0133] 516 Longitudinal axis

[0134] 518 wall

[0135] 520 inner circumferential surface

[0136] 522 cavity

[0137] 524 first wall section

[0138] 526 second wall section

[0139] 528 Profile

[0140] 530 Overlap

[0141] 532 Outside

[0142] 534 Inside a Wedge angle on the profile d Diameter (cross-section of 2nd wall section) dl Major axis length (cross-section of 2nd wall section) d2 Minor axis length (cross-section of 2nd wall section) t Effective thickness (1st wall section)

[0143] B Width of the strip or profile

[0144] Bl width (1st wall section)

[0145] B2 width (2nd wall section)

[0146] D Diameter of the inner peripheral surface

[0147] Hl height (1st wall section)

[0148] L2 Length (2nd wall section, radially outside)

[0149] L2 ' Length (2nd wall section, radial inside)

[0150] Rz roughness depth

[0151] TI wall thickness (1st wall section)

[0152] T2 wall thickness (2nd wall section)

Claims

PATENT CLAIMS:

1. Tubular plant cover (110, 210, 510) for forestry and fruit trees, which has an opening (112, 114; 212, 214) at each of the opposite ends and a wall (118, 218, 518) made of biodegradable material in between along a longitudinal axis (116, 216, 516), which wall, with an inner circumferential surface (120, 220, 520), defines a cavity (122, 222, 522) which is suitable for receiving a plant germ embedded in a substrate, from which a vital main root is to be formed in the plant cover (110, 210, 510), wherein the wall (118, 218, 518) has first and second wall sections (124, 126; 224, 226; 524, 526), ​​characterized in that the first and second wall sections (124, 126; 224, 226; 524, 526) consist of different materials that are biodegradable at different rates, or the wall (118, 218) is formed from radially inner and radially outer second wall sections (126,226) of greater wall thickness (T2) which extend substantially parallel to the longitudinal axis (116, 216), and first wall sections (124, 224) of smaller wall thickness (TI) which extend substantially radially with respect to the longitudinal axis (116, 226) and connect the second wall sections (126, 226) to one another, wherein the more rapidly biodegradable material or the smaller wall thickness (TI) of the wall (118, 218, 518) provides predetermined decomposition points at which, during the degradation of the plant cover (110, 210, 510), breakthroughs first occur in the wall (118, 218, 518), while the more slowly biodegradable material or the greater wall thickness (T2) of the wall (118, 218, 518) degrades the plant cover (110, 210, 510).

2. Tubular plant cover (110, 210) according to claim 1, characterized in 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.

3. Tubular plant cover (110, 210) according to claim 2, characterized in that the ratio of the height (Hl) 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.

4. Tubular plant cover (110, 210) according to one of the preceding claims, characterized in that the ratio of the smaller wall thickness (TI) of the first wall section (124, 224) of the wall (118, 218) to the average diameter (D) of the inner circumferential surface (120, 220) of the wall (118, 218) is in a range from 1:250 to 1:

25.

5. Tubular plant cover (110, 210) according to one of the preceding claims, characterized in that the smaller wall thickness (TI) of the first wall section (124, 224) of the wall (118, 218) is greater than or equal to 0.2 mm and less than or equal to 2.0 mm.

6. Tubular plant cover (110, 210) according to one of the preceding claims, characterized in that the ratio of the smaller wall thickness (TI) of the first wall section (124, 224) to the larger wall thickness (T2) of the second wall section (126, 226) is in a range from 1:1.1 to 1:3.

0.

7. Tubular plant cover (510) according to claim 1, characterized in that the wall (518) is formed by a profile (528) co-extruded from the different materials, which is helically arranged and, viewed in cross section, Substantially wedge-shaped longitudinal edges are wound around the longitudinal axis (516) in an overlapping manner, 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 rapidly biodegradable material.

8. Tubular plant cover (510) according to claim 7, characterized in that in the region of the overlap (530) with respect to the longitudinal axis (516) an outer side (532) of the profile (528) is glued or welded to an inner side (534) of the profile (528).

9. Tubular plant cover (210) according to one of the preceding claims, characterized in that at least two 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.

10. Tubular plant cover (210) according to claim 9, characterized in that four ribs (238) are formed on the wall (218) which project radially inwards in the direction of the longitudinal axis (216) and extend parallel to the longitudinal axis (216).

11. Tubular plant cover (210) according to claim 9 or 10, characterized in that the ribs (238) are formed in the biodegradable material of the wall (218) by means of a hot stamping process.

12. Tubular plant cover (210) according to claims 9 to 11, as far as related to at least claim 2, characterized in 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.

13. Tubular plant cover (110, 210, 510) according to one of the preceding claims, characterized in that the average roughness depth (Rz) on the inner peripheral surface (120, 220, 520) of the wall (118, 218, 518) is greater than or equal to 20 pm and less than or equal to 120 pm.

14. Tubular plant cover (110, 210, 510) according to one of the preceding claims, characterized in that the biodegradable material or materials of the wall (118, 218, 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 (110, 210, 510) according to one of the preceding claims for pre-cultivation and planting of forest and fruit trees.

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