Growing Medicinal Herbs in a Woodland Polyculture
Abstract: When individuals first learn about a new plant, many of them immediately are excited to have the plant in their landscape and look for a source of seeds and/or transplants to do so. What’s missing in many of these limitations is the fact that all plants grow in ecology of companion plants. The niche in which a species grows is filled with other plants that support it and the soil ecology. Taking a plant out of its natural environment and isolating it in pots or planting beds removes it from the supporting mechanisms that facilitate its growth. This is followed by reduced yields, disease, and reduction of the phytonutrients it might supply to its consumer. Cultivating these plants within a supporting ecology where all ecological functions are present and filled by plants with those functional roles may seem to reduce the yield, except for the fact that yields in aggregate of all the associated plants far exceeds that of the one.
Building a forest polyculture of any kind requires a considerable amount of planning and many sources of material to research the niche and species available to deliver human uses and ecological services. Keeping the final plant list to a minimum for the initial placement of the ecologically functioning species will help build a functional structure. After the initial 9 to 12 species are in place, including the over story, a number of shrubs, companion perennials, and a groundcover species, other plant species can be added.
Combining Chinese medicinal herbs into an existing ecological system of natural plant Associates increases the diversity of plant species, but also the disturbance regime frequency. If human harvesting is increased in the forest poly culture, ecologically supportive plants should also be increased. Nitrogen fixers, dynamic accumulators, and nurse plants will mitigate the removal of nutrients. It should be suggested that small patches of plants be implemented and studied prior to any large change in a forest ecosystem, that being said, the forest plants should be augmented with increased diversity, but still had a much smaller proportion than what already exists.
Thanks to the Natural Capital Plant Database, PFAF, USDA, and Changbin Chen, University of Minnesota
Woodland Medicinal Polycultures
The goal of this project is to augment agricultural forest woodland with ecologically functional plants and highly diverse sources of harvestable crops. The harvestable products from this forest garden will include food and medicinal crops[i] as well as increased ecological services and natural capital (E. Burkhart, 2007). A poly-culture design of associated species in a common niche will be based on high diversity and mutualistic mechanisms of facilitation. Plants will be placed in their proper niche relative to the partitions layers of the forest garden to be explained below. Not all the plants are perennials and some may need to be planted annually if not self-seeding.
The major resources are partitioned spatially and temporally to allow for extended growing periods and harvest. The major canopy plants will be dominated by existing trees in the growing space. The existing ecology is the design driver for selection of ecological analogues from available medicinal herbs. Using the available ecological functions and services within the plant patch, ecological requirements will be defined and used to select appropriate plants. Each plant selected will have one or more functional roles to contribute to the poly-culture. Priority will be given to plants that contribute to ecological function and have a medicinal use or harvest. Special consideration will be given to deciduous shrubs and perennials while low growing and ground cover plants may have limited human uses and be selected for soil health and production of organic material.
A literature review will be made of available research papers from the Agricola Database and other sources. Sources online from Cornell University and Ohio State[ii] have shown the incorporation of ginseng and ginger to existing hardwood forests. The motivation for this institutional research has been expansion of revenue-generating acreage in farming. It focuses on developing secondary and low maintenance crops within an existing ecology requiring little input or maintenance.
The structure, placement, density, and plant type(s) will be developed prior to species selection. This ensures that the functional roles required for successful poly culture will be defined and appropriate species will be found to fill those roles. Special attention will be made to effectively partition the resources of each niche and fill all layers of the forest structure.
The 1st layer is the tall tree canopy, the over story, the highest and tallest sun loving plants that begin to create shade. The canopy trees are the long term over story and for this project have been well established for many years in a healthy woodland. Care must be taken to not disturb the ecological services previously existing in the planting area or to cause stress to the trees involved. Long-term over story trees may consist of nut producing deciduous trees and or conifers such as Korean Nut Pine. In this case the major over story is Sugar Maple[v] which provides excellent ecological services for the production of Ginseng[vi]. Over story canopy can be as low as 5 feet or as high as 80 feet. The positioning of the plants in the forest layers are relative to its height, however ground-level layers have fewer extremes in mature height. Some large shrubs can be pruned to a tree form.
Some medicinal trees that fill this layer are:
5.Punica granatum (Pomegranate)
6.Terminalia chebula (16ºC Limit, Puerto Rico)
7.Sophora japonica (USDA 5b, N.Illinois, S. Iowa)
The 2nd layer is the low tree layer, trees that are tolerant of partial shade and fit under the over story canopy. Many times these are fruit trees or slow-growing over story trees that will extend higher after a disturbance or an opening in the canopy. Mulberry is an example of an understory tree, which tolerates partial shade, grows quickly, and produces well.
Medicinal trees for the partial shade tree layer include:
2.Eugenia caryophyllata (Cloves)
4.Morus rubra (Natural)
Next is the shrub layer, the 3rd layer of the forest garden. The shrub layer consists of deciduous and coniferous plants which are shorter in stature and fit beneath the canopy layers. The plants in the shrub layer consist of full sun, partial shade, and shade tolerant plants. It should be noted that although light tolerance is specified for many plants, it may also be a requirement for other plants. Some plants require full sun or require full shade. Other plants can tolerate full sun but may thrive and produce a higher-quality harvest in partial shade. It is important to place plants in their most optimized ecological niche. The 3rd layer may also include taller perennials such as Cup Plant and Anise Hyssop.
The 3rd layer is shrubs plants, medicinals include:
4.Morus rubra (Shaped)
The 4th layer is the herb layer. At this point the diversity and density of plants increases filling in the sunlit and shaded gaps between the trees and shrubs. Many of the ecological functions and services are provided by the herb layer as it supplies beneficial habitat and alternative food sources to beneficial insects. Each layer in the forest garden has opportunities for medicinal harvest, however the great diversity of the herbaceous layer supplies the largest share of medicinal and food crops. The herbaceous layer can be planted to a high density, some plants will be removed at harvest and others will remain to fill in the gaps. A managed succession may also be implemented to propagate plants.
The selection for plants in the low herb layer is vast. These are some perennials and annuals[vii].
1.Panax quinquefolius L. (P)
2.Agastache rugosa (A)
3.Artemisia annua - L. (A)
4.Astragalus mongholicus - Bunge. (P)
5.Codonopsis pilosula (P)
6.Cuscuta chinensis (P)
7.Glycyrrhiza uralensis (P)
8.Rehmannia glutinosa (P)
9.Salvia multiorrhiza (P)
10. Sesamum indicum (A)
11. Stachys affinis (P)
12. Vigna unguiculata cylindrical (A, NF)
The ground cover[viii] layer is the 5th layer in the forest garden. These are the shortest plants whose main function is to cover the soil spreading laterally. It is easily integrated with the herbaceous layer, as the plants will expand themselves in and around all the other plants and trees. As opposed to the herbaceous, shrub, or tree layers this is the 1st layer with grasses, but since grasses compete for resources with all the other plants, densities are minimum[ix] and they are used for beneficial habitat in clumps.
1.Rheum officinale (P)[x]
The 6th layer moves vertically back towards the canopy. This is the vine layer where plants rely on the structure of trees and other plants to move themselves into the sunlight. The vine layer is supported primarily by the trees filling a niche along their trunks and branches. Integration of vines into the forest canopy requires some management over time to ensure the vine does not compete with its host plant. There are many vines to choose from with varying growth habits and ecological functions. Some vines may also be ground cover and spread laterally. Many vine crops in annual gardens actually came from the forest edge which was their native niche. Growers may choose to integrate annual crops with the forest guard to increase its production. Curcubits such as squash and cucumbers grow well under these conditions a partial shade.
Vine crops are valued since they take little space and extend the growing area.
The final and 7th layer is the root layer. This layer is many times ignored by growers, but has the biggest effect on all the other plants relative to how it is used. Root crops also build the soil, breaking it up for water and oxygen infiltration. Some of the most nutritious and densest crops are root crops that can grow in partial shade, be stored in the ground, and harvested when needed. The root layer is partitioned between the plants so that competition for resources is minimized. With all the other plants of the other layers, their root type must be managed as it fills the three-dimensional space underground. Some of the roots may be fibrous and run close to the surface while others are Roots that run narrow and deep into the soil bringing up minerals. Tuberous roots and bulbs can be left to grow for years in some cases, while others must be picked frequently to ensure plant health. Understanding the type of roots and their spatial relationships within the polyculture will help place them for optimum use of the soil. It should be noted that even though a plant might be a member of one of the layers, it may also have an effect on or take space in other layers. Many of the perennial and herbaceous plants will have root crops harvested from the root layer and products for human uses from above the ground.
Once the existing structure of the forest garden is understood and the original condition in which new plants will be integrated is observed, plant selection can begin. In this ginseng polyculture, a sugar maple ecology has been found to be well suited by its ecological characteristics which parallel the Ginseng requirements. Along with Ginseng however, a list of other medicinal may be planted to fill the niche with diverse species. This builds resilience in the ecology as weather, seasons, and climate change. Intra-species competition and disease requires that ginseng be planted with wide dispersion (R.C.Vaughn, 2011).
The subsequent designs below reflect the diversity of plants to fit the partitioned resources available while protecting the soil and returning nutrients to the ecology. A majority of the plants are suitable to USDA Growing Zone 7 or above, but may be used as annual plants or in protected micro-climates.
The spatial displacement is relative to the required photoperiod as stated above in the layers. Sun tolerant or requiring plants may be on the edge of the layer, while shade tolerant or requiring plant can be the deep understory taking advantage of humidity and moist soils.
[i] D. Hosack, Organic Production and Marketing of Forest Medicinals: Building and Supporting a Learning Community Among Growers, 2008, Rural Action, P.O. Box 157, Trimble, OH Sustainable Agriculture Research and Education (SARE) program, which is funded by the U.S. Department of Agriculture
[ii] Colin Donohue, Sustaining Farms and Biodiversity through Woodland Cultivation of High-Value Crops, 2000, Conservation-Based Development Director, Rural Action Sustainable Forestry
1. Hankins, Andy, Producing and Marketing Wild Simulated Ginseng in Forest and Agroforestry Systems, 2000. Virginia Cooperative Extension Publication number 354-312, (currently posted at http://www.ext.vt.edu/pubs/forestry/354-312/354-312.html
2. Adam, Katherine L., ATTRA publication number IP115, Ginseng, Goldenseal and Other Native Roots,
October 2004. (posted at http://attra.ncat.org/attra-pub/ginsgold.html)
3. Carroll, Chip and Dave Apsley, Ohio State University Extension Fact Sheet F-56-04, Growing American
Ginseng in Ohio: An Introduction. (http://ohioline.osu.edu/for -fact/0056.html)
[iii] (B. Mollison, Permaculture, A Designers Manual, 1998, Kagari Publishing, Melbourne, AU
[iv] R. A. De J. Hart, Forest Gardening: Cultivating an Edible Landscape, 1998 Green Books, White River Junction, Vermont
[v] C.Campbell, L.Staats, and B. Beyfuss, Ginseng Research Projects, 1998, Uihlein Sugar Maple Field Station, Cornell Cooperative Extension
[vi] E. Burkhart ,Opportunities from Ginseng Husbandry in Pennsylvania, 2007, Pennsylvania State University,
112 Agricultural Administration Building, University Park, PA
[vii] R. C.Vaughan, Growing American Ginseng (Panax quinquefolius) in Forestlands, 2011, Forest Resources and Environmental Conservation, Virginia Tech
[viii] D. Sliwa, An Evaluation of Interplanted / Mulched Orchard Rows, 2002
Sustainable Agriculture Research and Education (SARE) program, which is funded by the U.S. Department of Agriculture
[ix] R. C.Vaughan, Growing American Ginseng (Panax quinquefolius) in Forestlands, 2011, Forest Resources and Environmental Conservation, Virginia Tech
[xi] C. Marsh, Plants For A Future, 1996 – 2007 Priory Park Road, Dawlish, Devon EX7 9LX (http://www.pfaf.org/user/default.aspx)