Method for removing harmful vegetation such as spartina alterniflora by using phenological characteristics

Abstract

The invention provides a method for removing and treating harmful vegetation such as spartina alterniflora by using phenological characteristics, and provides a natural-based solution (NbS) by using biological phenological characteristics in combination with actual growth conditions and engineering cases of the spartina alterniflora. On one hand, the control opportunity is accurately butted with the key phenological periods (such as a seedling period, an elongation period, a blooming period and a seed maturation period) of the spartina alterniflora, and on the other hand, the phenological difference between the spartina alterniflora and the reed of the same gramineae which is most likely to be mixed and difficult to distinguish is fully utilized, and the reed which is most fragile, most likely to kill and difficult to distinguish is selected. And intervention is carried out on a time window which has the minimum influence on an ecological system, so that the efficient, environment-friendly and sustainable treatment target is achieved.

Description

TECHNICAL FIELD

[0001] The present application mainly belongs to the technical field of agricultural plant protection, and specifically relates to an efficient and precise harmful vegetation removal method which fuses the principles of ecological phenology and precision agriculture technology, and selects the best prevention and control time by identifying the phenological differences between Spartina alterniflora and reed. BACKGROUND

[0002] Spartina alterniflora is listed as the first batch of invasive species in China, and its prevention and eradication has become an urgent task for ecological protection and restoration in coastal areas. At present, the removal methods of Spartina alterniflora mainly include physical method and chemical method. The physical method includes manual / mechanical mowing + deep burying, plowing / plowing, shading method, and waterlogging method. The chemical method mainly uses high-efficiency herbicides (such as high-efficiency fluazifop-butyl, imidazolinic acid, etc.) for spraying or shooting.

[0003] In the traditional prevention and control of Spartina alterniflora, the following problems exist: Blind application / operation: Generally, chemical or mechanical weeding is used on a regular basis and on a large scale, without considering the specific growth stage of weeds, resulting in poor effect or resource waste.

[0004] Environmental hazards: The use of broad-spectrum herbicides at non-optimal times not only kills Spartina alterniflora, but also harms crops, destroys soil microbial communities, and causes pesticide residues and environmental pollution.

[0005] Drug resistance: Continuous but imprecise use of drugs can easily select weed populations with drug resistance, making subsequent prevention and control more difficult.

[0006] “One-size-fits-all” model is ineffective: For weeds similar in shape to crops or with highly overlapping growth cycles, traditional methods are difficult to effectively distinguish, with high risk of injury.

[0007] At present, China has begun to carry out large-scale prevention and control of Spartina alterniflora, but due to the strong reproduction and spread of Spartina alterniflora, with the recovery of native vegetation reed, it will show the trend of continuous and scattered Spartina alterniflora and sporadic distribution mixed with reed on a large scale, and an efficient and precise removal method is urgently needed. SUMMARY

[0008] In view of the problems of poor effect, resource waste, environmental hazards, and drug resistance caused by the “one-size-fits-all” model in the process of Spartina alterniflora removal, the present application proposes a method for removing harmful vegetation such as Spartina alterniflora using phenological characteristics. The method is a natural-based solution (NbS) based on biological phenological characteristics, and the method includes the following steps: S1: Investigate the phenological characteristics of Spartina alterniflora and native symbiotic vegetation in the management area, determine the growth season, key phenological stage of Spartina alterniflora, and the phenological difference with native symbiotic vegetation, and measure and record the total biomass, aboveground biomass and underground biomass change data of the two in different months; S2: Based on the phenological characteristics and biomass data of S1, determine the removal window period of Spartina alterniflora; The window period needs to meet the physiological fragile period of Spartina alterniflora sensitive to removal measures, the stronger resistance period of native vegetation, and the higher discrimination degree with native symbiotic vegetation, that is, the time period when the biomass of Spartina alterniflora is lower than that of native symbiotic vegetation and has not entered the key reproduction period; S3: According to the distribution scale, density, mixed growth of Spartina alterniflora and the environmental sensitivity of the management area, select physical removal or chemical removal method; S4: In the removal window period determined in S2, implement the selected removal method to complete the removal of Spartina alterniflora; The operation parameters of physical removal or chemical removal need to match the phenological state of Spartina alterniflora at this period to ensure the removal efficiency and not to damage the native symbiotic vegetation.

[0009] As a preferred solution, in step S1, the phenological characteristics of Spartina alterniflora are as follows: The growth season is from April to November, the return green period is from April to May, the jointing period is from May to July with rapid growth, the flowering period is from July to August, the new rhizome has the ability of vegetative reproduction after August, the seed formation period is in September, the seeds mature in October, and the plants gradually wither after November; The native symbiotic vegetation is Phragmites australis, and its phenological characteristics are as follows: The growth season is from March to November, the return green period is from March to April, the vegetative growth period is from April to June, the jointing and earing period is from July to August, the flowering period is from August to September, the seeds mature from October to November, and the plants gradually wither in December.

[0010] As a preferred solution, in step S2, the removal window period is determined by the following biomass difference: Mechanical deep plowing window period: March, at this time, the biomass of Spartina alterniflora and Phragmites australis is the lowest, and Phragmites australis develops earlier than Spartina alterniflora, the aboveground morphology is obviously distinguished, and the Phragmites australis seedlings can be avoided from being damaged; Mowing window period: early August, at this time, Spartina alterniflora has not completed vegetative growth, its vegetative growth is completed after mid-August, and it avoids the peak period of Phragmites australis biomass in July, which can reduce the damage to Phragmites australis; Chemical application window period: July (first time), August (second time), and September (supplement), in July, the tolerance of Phragmites australis to chemical agents is significantly higher than that of Spartina alterniflora, in August, the underground biomass of Spartina alterniflora grows fast and the drug absorption efficiency is high, and in September, the aboveground biomass of Spartina alterniflora is the highest and has the maximum discrimination degree with Phragmites australis.

[0011] As a preferred solution, in step S3, the selection criteria for the physical control method are: When Spartina alterniflora is distributed in patches, the management area is an ecologically sensitive area or has protection requirements for indigenous vegetation, the physical control method is selected. The physical control method includes mowing + plowing and deep burying, and the operation time is strictly matched with the phenological window period determined in S2.

[0012] As a preferred solution, the specific operation parameters of the physical control are set based on the phenological period: Mowing: implemented in early August, stubble height ≤10 cm; Plowing and deep burying: implemented in March (Spartina alterniflora withering period, underground rhizome activity decreases), plowing depth 30-50 cm, after removing visible rhizomes, surface soil with residual rhizomes is deeply buried ≥150 cm, and surface layer is covered with soil ≥50 cm.

[0013] As a preferred solution, in step S3, the selection criteria for the chemical control method are: When Spartina alterniflora is sporadically distributed, mixed with reed, the environmental sensitivity of the management area is low, and there are no special protection requirements, the chemical control method is selected. The application time of the chemical control is strictly limited to the 7-9 month window period determined in S2, and the application time needs to avoid the sensitive phenological period of reed (reed biomass starts to decrease after July, but the tolerance is still strong).

[0014] As a preferred solution, the specific operation of the chemical control is matched based on the phenological period and the characteristics of the pesticide: Pesticide selection: 25% imidazole nicotine acid aqueous solution or 10.8% high-efficiency fluazifop-butyl preparation, and the area with Halodule pinifolia distribution prefers to use 10.8% high-efficiency fluazifop-butyl; Application amount: 25% imidazole nicotine acid aqueous solution is 1000-1500 ml / acre, and 10.8% high-efficiency fluazifop-butyl preparation is 120-180 ml / acre; Application method: using plant protection unmanned aerial vehicle or artificial backpack sprayer, when using unmanned aerial vehicle, add 1-2 kg / acre (high-efficiency fluazifop-butyl) or 40-80 kg / acre (imidazole nicotine acid) water, and add organic silicon spreading agent; the application needs to be carried out under the condition that the exposed beach time is ≥6 hours after the ebb tide and the wind force is ≤4 levels, and it is ensured that there is no precipitation or tidal disturbance within 6 hours after spraying; Application frequency: 25% imidazole nicotine acid aqueous solution is applied 1-2 times in a growing season, and 10.8% high-efficiency fluazifop-butyl is applied 3 times in a growing season, and the supplementary application time is selected in September (when the above-ground biomass of Spartina alterniflora is the highest, the adsorption rate of the pesticide is high).

[0015] As a preferred solution, the method is also applicable to the treatment of harmful vegetation in the field of agriculture, wherein step S1 is replaced by: establishing a database of phenological characteristics of harmful vegetation and crops in the target area, recording the germination period, seedling period, rapid growth period, flowering period, fruiting period and yellowing period of both, and measuring and recording the total biomass, aboveground biomass and underground biomass change data of both in different months; step S2 is replaced by: determining the overlapping time period of "harmful vegetation in the seedling stage / initial rapid growth stage (vulnerable period), crops in the strong tolerance growth period (safe period), harmful vegetation before flowering (propagation blocking period)" as the treatment window period.

[0016] As a preferred solution, the method also includes a post-treatment phenological monitoring step: During the growth season of Spartina alterniflora (April-November), the recurrence of Spartina alterniflora (plant height, density) and the growth status of reed in the treatment area are monitored every month. If Spartina alterniflora is found to have recurred, the corresponding treatment measures are selected according to the current phenological period: manual removal is used during the greening period (April-May), additional mowing is used during the jointing period (May-July), and additional pesticide application is used before the flowering period (July).

[0017] As a preferred solution, in step S4, the treatment operation also needs to match the tidal phenology of the treatment area: mechanical deep plowing and plowing for deep burial are implemented during the ebb tide period to ensure that the work is completed within one tidal cycle; Chemical pesticide application is selected to be implemented 4-6 hours before the high tide to avoid loss of the pesticide due to washing by the tidal water, and the withered and fallen plant matter on the Spartina alterniflora plants needs to be removed before pesticide application to ensure that the pesticide directly contacts the living plants.

[0018] The beneficial effects of the present application are: The present application precisely connects the treatment opportunity with the key phenological periods of Spartina alterniflora (such as the seedling stage, the jointing stage, the flowering peak period, and the period before seed maturation), selects the "time window" when it is most vulnerable, most easily killed, and has the least impact on the ecological system, and thus achieves the goal of efficient, environmentally friendly, and sustainable treatment. The present application has the following advantages: (1) Dimensional improvement from "space" to "space-time": traditional precision agriculture mainly focuses on spatial variation (where the harmful grass is), and the present patent introduces temporal variation (when is the best time to control weeds), achieving two-dimensional space-time precision management; (2) High targeting: "time-dependent pesticide application" and "grass-dependent strategy" are achieved, significantly improving the killing efficiency; (3) Environmentally friendly: the use amount and frequency of chemical pesticides are greatly reduced, and the pollution risk to the ecological environment and agricultural products is reduced; (4) Economically efficient: improving the control effect means reducing repeated work, saving manpower, material resources and financial resources; (5) Strong sustainability: by blocking reproduction, it can control the population number of harmful vegetation from the source, which is an effective way to achieve ecological sustainable management; (6) Solve problems: especially suitable for preventing and controlling those malignant weeds that have long symbiotic period with crops and similar morphology. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The figure is the seasonal variation of the biomass of reed and Spartina alterniflora.

[0020] Figure 2 The figure is the process photo of the first sample plot in the physical control area.

[0021] Figure 3 The figure is the process photo of the second sample plot in the physical control area.

[0022] Figure 4 The figure is the process photo of the third sample plot in the physical control area.

[0023] Figure 5 The figure is the process photo of the fourth sample plot in the physical control area.

[0024] Figure 6 The figure is the process photo of the first sample plot in the chemical control area.

[0025] Figure 7 The figure is the process photo of the second sample plot in the chemical control area.

[0026] Figure 8 The figure is the process photo of the third sample plot in the chemical control area.

[0027] Figure 9 The figure is the process photo of the fourth sample plot in the chemical control area. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below according to the drawings and specific examples.

[0029] The implementation area of the present application is the Spartina alterniflora control project in the beach shore section of Chongming region in Shanghai. The distribution characteristics of Spartina alterniflora in the project control area are divided into physical control area and chemical control area.

[0030] Example 1 (physical control area) Start time: March 2024.

[0031] The physical method is used to control Spartina alterniflora, and the significant difference feature time of the aboveground biomass of Spartina alterniflora and reed is mainly focused on as the window period. The operation time of mechanical deep plowing is selected when the biomass of Spartina alterniflora is the lowest, and at the same time, there is a clear distinction between reed. The mowing time should be before the completion of the vegetative growth of Spartina alterniflora, and at the same time, it should avoid the time when the biomass of reed is the highest.

[0032] According to Figure 1 It can be seen that the biomass of reed and Spartina alterniflora is the lowest in March, but reed sprouts earlier than Spartina alterniflora. In order to protect the growth of reed as much as possible, the operation time of mechanical deep plowing is selected in March when the difference in aboveground is more obvious. Only the area where reed sprouts have not yet emerged is mechanically deep plowed, and the area where reed sprouts have emerged is not mechanically deep plowed. The total biomass and aboveground biomass of reed are the highest in July, so it is recommended to avoid cutting in July; Spartina alterniflora completes vegetative growth in mid-August, so cutting is selected in early August.

[0033] Example 2 (chemical control area) Start time: July 2024 Chemical control of Spartina alterniflora is mainly based on the significant difference characteristics of total biomass, aboveground biomass and underground biomass of Spartina alterniflora and reed as the window period. The first application selects the time when the total biomass and underground biomass of reed are higher than those of Spartina alterniflora, and reed has stronger tolerance to chemical agents. The second application selects the time when the underground biomass and total biomass of Spartina alterniflora increase rapidly, which is the vegetative growth period of Spartina alterniflora. The supplementary application selects the time when the aboveground biomass of Spartina alterniflora is relatively high.

[0034] According to Figure 1 It can be seen that the total biomass of reed is higher than that of Spartina alterniflora in July, and there is a more obvious difference in tolerance to chemical agents, so July is selected as the first application time. In August, the underground biomass and total biomass of Spartina alterniflora increase rapidly, and the absorption of drugs is faster, so August is the best time for the second application. In September, the aboveground biomass of Spartina alterniflora is the highest, and the difference with reed is the most obvious at this time, which is easy to distinguish. At the same time, the higher aboveground part has better adsorption and absorption of drugs, so September is the best time for supplementary application.

[0035] Monitoring during the control process (1) Global range monitoring The unmanned aerial vehicle remote sensing technology uses unmanned aerial vehicles equipped with remote sensing cameras and other sensors to obtain and measure the distribution, growth and coverage area of Spartina alterniflora with high resolution, and provides detailed geographic spatial information, so as to better understand the distribution of Spartina alterniflora and its changes before and after application. By using unmanned aerial vehicle remote sensing technology, the control effect of Spartina alterniflora on the beach can be monitored quickly, in real time and efficiently, but the ability to identify individual Spartina alterniflora is weak due to the flight height when shooting full range images.

[0036] (2) Spot check of control effect The unmanned aerial vehicle remote sensing technology is used to arrange the sampling points and take photos in the treatment plot. The flight height is low, and the image is clear. Through the high-precision unmanned aerial vehicle remote sensing image, the single Spartina alterniflora plant in different sampling points of the treatment plot can be identified and located, providing specific and accurate treatment information for the managers.

[0037] The high-precision unmanned aerial vehicle photos are taken in the Spartina alterniflora treatment area to check the treatment situation. The DJI Sikong 2 platform is used to arrange the flight routes in the Spartina alterniflora mowing + plowing and deep burying (physical treatment) area, so that each flight route passes through the entire treatment area.

[0038] After the flight route is arranged, 5 squares of 15m x 15m are taken at equal intervals in the flight route, with an area of 225 square meters. The square is symmetrically arranged around the sample strip and has a north-south elevation change. The flight height of the unmanned aerial vehicle is 12 meters relative to the takeoff point, the overall flight speed is 3.6 meters per second, the lateral overlap rate is 70%, and the heading overlap rate is 80%. According to the flight angle, 25-30 photos are taken for each square to obtain the orthographic image of each sampling point. At present, the flight route in the North Lake physical treatment area is set to 8, with a total of 40 sampling points, covering an area of 9000 square meters, which covers the physical treatment area well.

[0039] The unmanned aerial vehicle photos taken are spliced using the DJI mapping software to obtain the complete orthographic raster image of the sampling point. In Arcgis, a vector layer is created, the plane coordinates and datum projection are unified, and the Spartina alterniflora that has not been removed in the sampling point is manually checked in combination with the complete orthographic image and photos. The obtained patches are calculated for coordinates and area, and finally the partition removal rate and total removal rate are calculated.

[0040] After the mechanical deep plowing is completed in March 2024, the investigation is carried out, and the removal rate is 98.30%. After the mowing is completed in early August, the removal rate reaches 100.00% at the end of August when the work is completed and accepted.

[0041] After the second pesticide application is completed in August 2024, the investigation is carried out, and the Spartina alterniflora in the pesticide treatment area is removed as a whole, but there are still a small amount of Spartina alterniflora residues, with a removal rate of 99.70%. After the supplementary pesticide application is completed in September, the overall removal rate is 99.85%.

[0042] Combined with the results of remote sensing monitoring and plot investigation, as of August 2024, the removal rate in the Spartina alterniflora treatment area is more than 95%. In May and July 2025, two times of sampling are carried out to check the recurrence in the treatment area, and the overall recurrence rate is less than 5%.

Claims

1. A method for controlling harmful vegetation such as Spartina alterniflora by utilizing phenological characteristics, characterized in that, Includes the following steps: S1: Investigate the phenological characteristics of Spartina alterniflora and native symbiotic vegetation in the treatment area, clarify the growing season, key phenological stages of Spartina alterniflora and the phenological differences between it and native symbiotic vegetation, and measure and record the changes in total biomass, aboveground biomass and underground biomass of the two in different months. S2: Based on the phenological characteristics and biomass data of S1, determine the control window period for Spartina alterniflora; the window period should meet the following conditions: Spartina alterniflora is in a physiologically vulnerable period that is sensitive to control measures, native vegetation is in a period of strong resistance, and the difference between it and native symbiotic vegetation is high. Specifically, it is the time period when the biomass of Spartina alterniflora is lower than that of native symbiotic vegetation and has not entered the critical period of reproduction. S3: Select physical or chemical control methods based on the distribution scale, density, mixed growth of Spartina alterniflora and the environmental sensitivity of the treatment area; S4: Within the control window period determined in S2, implement the selected control methods to complete the control of Spartina alterniflora; among them, the operation parameters of physical or chemical control must be matched with the phenological state of Spartina alterniflora at that time to ensure control efficiency and without damaging native symbiotic vegetation.

2. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, In step S1, the phenological characteristics of Spartina alterniflora are specifically as follows: The growing season is from April to November. April to May is the greening period, May to July is the jointing period accompanied by rapid growth, July to August is the flowering period, after August the new rhizomes have the ability to reproduce asexually, September enters the seed formation period, October the seeds mature, and after November they gradually wither. The native symbiotic vegetation is reed, and its phenological characteristics are as follows: The growing season is from March to November. March to April is the greening period, April to June is the vegetative growth period, July to August is the jointing and booting period, August to September is the flowering period, October to November is the seed maturation period, and December is the gradual withering period.

3. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, In step S2, the treatment window period is determined by the following biomass differences: Mechanical deep tillage window period: March, when the biomass of both Spartina alterniflora and Phragmites australis is at its lowest, and Phragmites australis sprouts and develops earlier than Spartina alterniflora, with clear distinction in aboveground morphology, which can avoid damaging Phragmites australis seedlings. Cutting window: early August. At this time, Spartina alterniflora has not yet completed its vegetative growth. Its vegetative growth is completed after mid-August. Cutting should be done in July when the biomass of reeds is at its peak, which can reduce accidental damage to reeds. Chemical application windows: July (first application), August (second application), and September (supplementary application). In July, reeds showed significantly higher tolerance to chemical agents than Spartina alterniflora. In August, Spartina alterniflora experienced rapid underground biomass growth and high agent absorption efficiency. In September, Spartina alterniflora had the highest aboveground biomass and was most distinct from reeds.

4. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, In step S3, the selection criteria for the physical removal method are as follows: When Spartina alterniflora is distributed in large patches, or when the treatment area is an ecologically sensitive area or where there are requirements for the protection of indigenous vegetation, physical control should be chosen. The physical control method includes mowing and deep burial, with the operation time strictly matching the phenological window period determined by S2.

5. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 4, characterized in that, The specific operational parameters for the physical treatment are set based on the phenological period: Harvesting: to be carried out in early August, with a stubble height of ≤10cm; Deep tillage and burial: Implemented in March (when Spartina alterniflora withers and the activity of underground rhizomes decreases). Tillage to a depth of 30-50cm. After removing visible rhizomes, bury the topsoil with residual rhizomes to a depth of ≥150cm, and cover the surface with plain soil to a depth of ≥50cm.

6. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, In step S3, the selection criteria for the chemical treatment method are as follows: When Spartina alterniflora is sparsely distributed, severely mixed with reeds, and the treatment area has low environmental sensitivity and no special protection requirements, chemical control should be chosen. The application time for chemical control is strictly limited to the window period of July to September determined by S2, and the application should avoid the sensitive phenological period of reeds (after July, the biomass of reeds begins to decline, but their tolerance is still relatively strong).

7. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 6, characterized in that, The specific operation of the chemical control is based on matching the phenological period with the characteristics of the pesticide: Pesticide selection: 25% imidacloprid aqueous solution or 10.8% high-efficiency flupyridine formulation, with 10.8% high-efficiency flupyridine preferred in areas where Scutellaria barbata is distributed; Application rate: 1000-1500 ml / mu for 25% imidacloprid aqueous solution, and 120-180 ml / mu for 10.8% high-efficiency flupyradifurone formulation; Application method: Use plant protection drones or manual backpack sprayers. When applying with drones, dilute with 1-2 kg / mu (high-efficiency flupyridine) or 40-80 kg / mu (imidazolium nicotinic acid) and add organosilicon spreading agents. Application should be carried out after the tide has receded and the exposed beach time is ≥6 hours and the wind force is ≤4, and ensure that there is no precipitation or tidal interference within 6 hours after spraying. Application frequency: Apply 25% imidacloprid aqueous solution 1-2 times per growing season, and apply 10.8% high-efficiency flupyradifurone 3 times per growing season. The best time for supplementing is in September (when the biomass of Spartina alterniflora is at its highest and the pesticide adsorption rate is high).

8. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, The method is also applicable to the control of harmful vegetation in the agricultural field. In this case, step S1 is replaced by: establishing a phenological characteristic database of harmful vegetation and crops in the target area, recording the germination period, seedling period, rapid growth period, flowering period, fruiting period and withering period of both, and measuring and recording the changes in total biomass, aboveground biomass and underground biomass of both in different months; step S2 is replaced by: determining the overlapping time period of "harmful vegetation in the seedling stage / early stage of rapid growth (vulnerable period), crops in the growth period of strong tolerance (safe period), and harmful vegetation before flowering (reproduction blocking period)" as the control window period.

9. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, It also includes post-treatment phenological monitoring procedures: During the growing season of Spartina alterniflora (April-November), the recurrence of Spartina alterniflora (plant height, density) and the growth status of reeds in the treated area are monitored monthly. If Spartina alterniflora recurrence is found, corresponding control measures are selected according to the current phenological stage: manual removal is used during the greening stage (April-May), additional cutting is carried out during the jointing stage (May-July), and additional application of pesticides is carried out before the flowering stage (July).

10. The method for controlling harmful vegetation such as Spartina alterniflora using phenological characteristics according to claim 1, characterized in that, In step S4, the treatment operation also needs to be matched with the tidal phenology of the treatment area: mechanical deep plowing and deep burial should be carried out during the low tide period to ensure that the operation is completed within one tidal cycle; Chemical application should be carried out 4-6 hours before high tide to avoid the pesticide being washed away by the tide. Before application, withered and fallen leaves on the Spartina alterniflora plants should be removed to ensure that the pesticide comes into direct contact with the living plants.

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