Part 1
Introduction
Why have a medicinal forest garden? In this introduction I explain the nature of a forest garden and explore the great potential of cultivating a medicinal forest garden. There is a compelling case for growing more medicinal plants sustainably, especially woody plants such as trees and shrubs. This case is supported from both economic and environmental perspectives. I provide an overview of increasing demands for medicinal plants worldwide and outline the threats to medicinal plant supplies due to habitat loss, climate change and overharvesting. At the end of this introduction, there is information about the structure of this book which may be helpful if you are deciding which parts of this book to read first.
The nature of forest gardens
The term ‘forest garden’ has been in use since the 1990s1 although some writers have used other terms since, such as the ‘woodland garden’ and ‘food forest’.2 A forest garden is not just a collection of trees. Rather, it is the way in which these plants are brought together and managed that is characteristic of a forest garden. A forest garden can take many forms but is essentially ‘a garden modelled on the structure of young natural woodland’.3 To fully understand the nature of a forest garden, there are three key aspects to consider. First, the form of the forest garden draws on natural growth patterns, particularly in having multi-layered or ‘stacked’ plant species which are integrated in various ways. Second, the forest garden is managed to a greater or lesser extent, particularly in terms of promoting soil health and diversity, and the management approach often draws on natural regenerative processes. Third, productivity in the forest garden is achieved in a sustainable way, primarily through ongoing supplies of foods that are harvested from a wide variety of plants.
The forest garden provides an environment that benefits soil organisms, perennial roots, fertility and availability of nutrients, and water management.4As leaves die off and accumulate as a mulch, and as roots die back, decomposition by micro-organisms provides nitrogen and other nutrients for the soil. Benefits from a forest garden style of cultivation include increased productivity, shade, improved soil management, pest and disease control, increased biodiversity and pollination, microclimate modification, water management and carbon sequestration.5 Many writers on forest gardens refer to a classical model of seven layers, from the upper canopy to the understorey and lower levels of shrubs, herbaceous plants, ground cover plants, roots and climbers. This level of categorisation can be much further subdivided, indeed ‘the opportunities to fill every niche are endless’.6 The forest garden has been described as ‘a deliberately designed, high yielding, perennial plant system’ for human sustenance.7 A frequently used term is ‘food forest’, reflecting the primary focus on food crops such as leaves, fruit and nuts produced from a multi-layered woodland project.
What is a medicinal forest garden?
At Holt Wood, we started to use the phrase ‘medicinal forest garden’ because it so aptly describes the diversity and many layers of healing plants that have flourished since planting the medicinal woodland in 2005. My working definition has evolved for this book as:
A medicinal forest garden is a natural or designed space including multi-layered plant species which is managed ethically and sustainably with potential for promoting health through a range of activities including harvest of medicinal plants.
This definition is deliberately broad in scope, in order to recognise that there can be many varied contexts for healing plants, from cottage gardens and parks to agroforestry and woodland. There is no ‘one size fits all’ medicinal forest garden! Medicinal plants, especially trees and shrubs, are often multifunctional and can co-exist within a forest garden having a wider range of purposes. Since health and diet are so closely intertwined, many food plants are recognised to have general health-promoting potential through their nutritional benefits (see Case Study: The Forest Garden).
case study: The Forest Garden – food & medicine together
Name: The Forest Garden
Location: Near Falmouth, Cornwall, UK
Activity: Founder of The Forest Garden, Simon Miles is knowledgeable about herbal medicine, having trained as a Master Herbalist. He also has a background in horticulture. This well-established forest garden, of just over three acres, is near the coast in Cornwall, in south west England. The forest garden has been designed to efficiently produce tasty food, and supplies from medicinal and other useful plants. Many of the plants have both nutritional and medicinal effects, and are used by Simon in his clinical practice. The planting setup reflects the range of plants that grow best in a maritime climate where there is a salty wind, although there are less frequent frosts. Experience has shown which plants are most likely to succeed including the top fruit of selected Cornish apple, Asian pear, almond and other nut trees. Alongside these trees are many perennial bushes and herbs that can be used as companion plants to form multiple layers in a low maintenance design. Edible landscape design advice is available on perennial plants to suit particular requirements, and is supported by education through courses, as well as supplies of some hard-to-find plants.
Key point: Herbal medicine and food can work well together in forest gardening layers.
Info: www.theforestgarden.co.uk
Simon Miles in his Forest Garden, Cornwall, UK
The Forest Garden has medicinal plant layers
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Resilience and forest gardening
A particular benefit claimed for forest gardening is increased resilience. The forest garden is likely to have greater biodiversity (range of species) and be designed with varied environments (range of light levels and soil characteristics), thus leading to greater resilience to climate extremes.8 Biodiverse planting may also prove beneficial in combatting climate breakdown in large-scale tree planting. An example from China has shown that the ‘richness’ (i.e. greater range) of plantation species strongly increases productivity, and more complex plots increase biomass production and accumulate more carbon, nearly twice as much over an eight-year period compared to monocultures.9 These results from research studies should encourage further multispecies forestry management strategies like forest gardening.
Threats to medicinal plant supplies
A significant threat is loss of habitat. Forests are particularly affected especially in tropical areas, and the range of threats includes increases in agriculture and settlements, fires and invasive plants, disturbances from war and mining.10 In 2015, almost 4 billion hectares (30.6%) of the land area in the world was covered by forests. Of this total forested area, between 1990 and 2015, the areas of planted forest increased from 4% to 7%, but primary forest areas decreased, particularly tropical forested areas, and these are areas of irreplaceable biodiversity.11 Actions to restore the planet’s trees include the Reduced Emissions from Deforestation and Forest Degradation (REDD+) initiatives as part of global climate protection, originally proposed in 1997. These initiatives provide financial incentives to developing countries for reducing emissions related to conversion of forests to other uses.12 REDD+ incorporates additional elements to focus on sustainable management and enhancement of forests, but full-scale implementation is yet to be achieved. The loss of habitat is a major source of concern in relation to medicinal plants. According to the State of the World’s Plants 2017,13 over a thousand important plant areas are under threat in Europe and the South Mediterranean, due to development and abandonment, agricultural intensification and inappropriate forest management. Tourism development is one of the most significant threats, due to disturbance and trampling or resort development with high impact in 136 locations.
Forests are also significantly affected by climate breakdown, not only by disruptive events of disturbances of heat, drought and storms but also by steady changes in the nature of climate.14 In the Atlantic coastal zone of Europe, forest productivity may be increasing in some mountain areas as temperatures rise but decreasing in areas prone to drought stress. Insect and fungal population increases may cause substantial losses.15 In the Continental zone of Europe, rising temperatures may mean greater productivity where sufficient water is available for trees to grow, but tree vitality will suffer in drier sites, especially where more wind, insect attacks and fungi are also likely. In the Mediterranean region, increasing carbon dioxide levels will enhance photosynthesis, perhaps increasing growth by 30-50% for young broadleaved trees.16 Overall, the distribution of tree species is likely to alter as trees become vulnerable to the changes.
While habitat loss and climate breakdown are the most significant threats to medicinal plants, the possibility of overharvesting remains a concern. It has been estimated that over 28,000 plants have medicinal uses worldwide.17 According to Traffic International,18 between 60-90% of medicinal plants are collected from the wild, particularly in forests, and conservation status is unknown for at least 93% of these species. Some 1280 medicinal plants are listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The CITES Secretariat has recognised that the greatest use of non-timber forest products is related to medicinal trade, and much of this trade is carried out through online networks that are particularly hard to trace.19 Efforts to regulate use of medicinal non-timber forest products through certification are made more complex due to the wide range of herbal products, their seasonality, different end uses and insecure harvesting rights.20 Alternatives to wild-harvested plants may be possible through cultivation for sustainable supplies, especially significant where these plants are ‘destructively harvested for their bark, roots or the whole plant’.21 Cultivation can include simulation of natural woodland environments, such as in developments supported in the US by United Plant Savers. This may be a way forward to protect some endangered species (see Case Study: United Plant Savers Botanical Sanctuary). An advantage of cultivating plants in conditions similar to the wild is the sustainable harvest, and controls can be applied to ensure organic or other suitable standards are maintained.22
case study: Conserving natural habitats with medicinal plants in the US
Name: United Plant Savers Botanical Sanctuary
Location: Center for Medicinal Plant Conservation, Ohio, US
Activity: Founded in 1994, United Plant Savers exists to promote medicinal plant conservation in the US. In Ohio, the Goldenseal Botanical Sanctuary provides a haven for plant lovers and all interested in the conservation of medicinal plants. Based on a 379 acre plot of land, previously degraded by mining activities, much of the site has been carefully planted and a new visitor centre has been opened. Visitors can follow marked medicine trails in the restored woodland, seeing medicinal trees and other healing plants. The Sanctuary also hosts demonstrations of shade cultivation and examples of prairie plants such as Echinacea species. An internship programme runs each year which provides an opportunity for visitors to become involved in the maintenance and development of the sanctuary. United Plant Savers advises on sustainable cultivation methods, and also maintains a list of ‘at-risk’ plants including woodland plants such as ginseng and goldenseal.
Key point: Restoration of natural habitats provides real opportunities to learn about the conservation of medicinal plants in the US.
Info: www.unitedplantsavers.org
Visitors can follow a medicine trail at the United Plant Savers (UPS) Botanical Sanctuary
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Potential for cultivating medicinal plants including trees and shrubs
The growing of medicinal plants on a small scale has considerable potential for increasing the supply of medicinal and aromatic plants in response to rising demand. Small woodlands can have a key role to play. In 2004, a survey published by Plantlife in the UK made recommendations that included support for cultivation through partnerships with small-scale growers.23 A recent European study suggests a role for agroforestry or agriculture with trees:
With dwindling supplies from natural sources and increasing global demand, the MAPs [medicinal and aromatic plants] will need to be cultivated to ensure their regular supply as well as conservation. Since many of the MAPs are grown under forest cover and are shade tolerant, agroforestry offers a convenient strategy for promoting their cultivation and conservation.24
The possibilities of further commercially exploiting by-products of forestry have been well established in the US context.25 There are numerous possible connections between markets for non-timber forest products in areas such as floristry and cosmetics as well as health care.
Goldenseal (Hydrastis canadensis) plant from sustainable cultivation in woodland
In the US, the potential for valuable medicinal crops has benefitted from advice and support to farmers and woodland owners. Since 2004, Jeanine Davis and colleagues at North Carolina State University, US, have been working with local farmers to produce medicinal herbs for commerce. Funds were made available to farmers, so that they learned to grow, harvest, clean, dry and market a range of herbs including ginseng (Panax quinquefolius) and goldenseal (Hydrastis canadensis).26 These crops can be profitable but farmers were unfamiliar with them and needed more support, from practical information through to research and shared-use facilities for processing. In the UK, surveys have previously identified a buoyant market for medicinal herbs but a lack of home production for a variety of reasons.27 The potential problems of low prices for raw materials and high labour costs of harvesting could be counteracted by identification of more efficient cultivation methods, co-operative processing and organic premiums, with ways of combining cultivation with other activities to provide an economic return.
Agroforestry and permaculture
Changing agricultural practices have brought rising interest in the potential of agroforestry. Part of the renaissance of such new approaches has been due to the success of permaculture design principles in creating productive sites, by drawing on examples from nature, and moving away from monocrop styles of growing. There is also an important ethical basis inherent in seeking to achieve more sustainable ways of growing and living. This can be seen in the three ethical principles associated with permaculture developments: they should be good for the planet (earth care), good for people (people care), and ensure that surplus produce is fairly used (fair shares). The transformational approach of permaculture is well adapted to fostering resilience as well as flexibility in response to change.28
St John’s wort (Hypericum perforatum) is sold over the counter as an antidepressant
Quality control and medicinal plants
An advantage of cultivation over wild-harvesting is the potential for producing top quality herb products. There have been concerns regarding the quality and provenance of herb supplies and products that are sold over the counter. In the UK, a study of St John’s wort (Hypericum perforatum) products, which used high performance thin layer chromatography alongside spectroscopy, found that over one-third (36%) of the products were adulterated.29 As in previous studies on ginkgo products, the commercial products of the highest quality were those with European traditional herbal registration licences rather than unlicensed products.30 In North America, a study based on DNA barcodes, including elder, ginkgo and walnut, found that only two out of 12 suppliers had products without plant substitution, use of fillers or contamination.31 If the costs of testing for purity could be reduced then such DNA testing could be used more widely to provide authentication of herbal products both in cultivation and wild-harvesting.32
Demand for medicinal plants worldwide
Although medicinal plants are used worldwide, just 12 countries make up 80% of world trade by value in medicinal plants, and the US, Germany and Hong Kong are the most important trade centres.33 The main exporters of medicinal plants are China, exporting over 1.3 billion kg in 2013, as well as India, Canada, Germany and the US. Most of the source countries, where herbs are harvested, export botanicals after little processing, dried and packed into large containers. The main importers by value are Hong Kong, China, the US, Germany and Japan.34 However, detailed statistics are not easy to come by for trade in the world herbal market, mainly because import and export data are poorly defined.35 A few plant species are specifically recorded in the data, such as liquorice and ginseng, but most of the remaining plants are categorised together as ‘medicinal and aromatic’ plants.
Even though the statistics may not be itemised in terms of individual medicinal plants, growth of interest in traditional and complementary medicine worldwide has become increasingly well documented in both industrialised and developing countries.36 In Europe, demand for herbal medicinal products has been rising: statistics published in March 201737 showed that retail sales in Germany in 2015 had increased 5.9% from the previous year, reaching 1.6 billion Euros. The top three categories of herbal remedies were products for coughs, respiratory tract diseases, and colds and flu, and altogether these three product categories accounted for over half of sales.38 Sales of some herbal supplements continue to be popular in the US, whether through supermarkets, health-food stores or mail order online. For example, supermarket sales of extracts of elderberry (Sambucus nigra) increased by 34.7% from 2016 to 2017.39
Demand for traceability and sustainability
Apart from over-the-counter herbal remedies for common complaints, medicinal and aromatic plants also feature strongly in personal care products. The global organic personal care market was estimated at US$10.16 billion in 2015, and rising consumer awareness is expected to drive further growth in sales of organic products.40 Growth potential in the market is evident for skin care, hair care, oral care and, particularly, anti-ageing products. Ironically, new innovations such as forest-derived health-related products and services, may contribute to growing the market in Western countries but may be damaging for the survival of some plants in the wild.41 Wild-harvesting is the main way in which these medicinal and other plants for health supplements and cosmetics worldwide are sourced for trade. This wild-harvesting trade can provide an important source of income for poor or disadvantaged people in rural communities, particularly women who rely on forest products.42 However, since demand for medicinal plants is likely to continue to rise, this will increase pressure on wild-harvested sources.43 Amongst consumers there is greater interest in provenance of ingredients in products,44 and growing numbers of people making as well as using natural remedies.45 This interest in sustainability is encouraging the natural products industry to improve the traceability of botanical supplies, making the supply chain more transparent.46 Progress is being made in reporting on sustainability by forward-looking herbal businesses such as Pukka Herbs and Weleda.47
Medicinal elder (Sambucus nigra) berries are in demand
About this book
This book is in two main parts. Part 1 consists of seven chapters that deal with general principles and advice, from designing with medicinal trees to harvest and use, with many practical examples. Chapter 1 provides a backdrop of how herbal medicines work, especially trees and their phytochemistry. At the end of Chapter 1 there is a quick access listing of the 40 trees and shrubs detailed in Part 2. If you want to design a medicinal forest garden then go straight to Chapter 2. If you are keen to focus on practical aspects of establishing and maintaining a medicinal forest garden then jump to Chapter 3. Propagation and sourcing of plants is covered in Chapter 4. For details of best practices in harvesting and making herbal preparations then see Chapters 5 and 6. Finally, Chapter 7 provides some suggestions regarding scaling up to a higher level of growing, including commercial possibilities. Part 2 provides a concise A to Z listing by Latin name of individual profiles of 40 trees and shrubs suitable for a temperate climate. Each profile entry provides details of the species relevant to successful cultivation, as well as advice on parts for harvesting, possible indications for use, and relevant research examples and other key information.
Sources used
Throughout this book there are reference sources, provided in the endnotes, and there is a selected bibliography. The Plant List hosted by Kew Gardens provides up-to-date accepted scientific plant names.48 Online sources such as the Plants for a Future database49 and North American horticultural information sites have provided much cultivation information. For clinical and scientific studies, keyword searches in PubMed have identified additional examples of published research in a range of disciplines from forestry to medicine and phytochemistry.50 This book focuses on the northern temperate climate for growing medicinal plants. The temperate zones have distinct summer and winter seasons, and native temperate forests are diverse, including conifers and deciduous trees. I have included several trees and shrubs which are almost hardy in these temperate areas if given some protection. These semi-hardy medicinal plants may have increasing potential for cultivation in a warming climate. I have excluded species that are more suitable for boreal, southern or tropical climates. All measurements are given in metric and there is a conversion table for metric and imperial measurements in Appendix 1. A glossary is provided in Appendix 2. Towards the end of the book are further useful appendices on herbaceous medicinal plants (Appendix 3), climate zones (Appendix 4 and 5) and links to organisations and other resources (Appendix 6).
1 Hart R. (1991) Forest Gardening, Bideford: Green Books.
2 Whitefield P. (2002) How to Make a Forest Garden, East Meon, Hampshire: Permanent Publications.
3 Crawford M. (2010) Creating a Forest Garden: Working with Nature to Grow Edible Crops, Totnes, Devon: Green Books, p17
4 Jacke D and Toensmeier E. (2005) Edible Forest Gardens: Ecological Design and Practice for Temperate Climate Permaculture, White River Junction, VT: Chelsea Green Publishing.
5 Smith J, Pearce BD and Wolfe MS. (2013) Reconciling productivity with protection of the environment: Is temperate agroforestry the answer? Renewable Agriculture and Food Systems 28: 80-92; Woodland Trust. (2018) Agroforestry in England: benefits, barriers and opportunities,www.woodlandtrust.org.uk/publications/2018/06/agroforestry-in-england/ (accessed 25 March 2019).
6 Weiseman W, Halsey D and Ruddock B. (2014) Integrated Forest Gardening: The Complete Guide to Polycultures and Plant Guilds in Permaculture Systems, White River Junction, VT: Chelsea Green Publishing, p13.
7 Weiseman et al. (2014) p11.
8 Crawford (2010) pp33-37 outlines the effects of climate change; The environmental challenges for individual trees are outlined in Hirons AD and Thomas PA. (2018) Applied Tree Biology, Hoboken, NJ: John Wiley, pp351-384.
9 Huang Y, Chen C and Castro-Izaguirre N. (2018) Impacts of species richness on productivity in a large-scale subtropical forest experiment. Science 362: 80-83.
10 Conway P. (2001) Tree Medicine: A Comprehensive Guide to the Healing Power of Over 170 Trees, London: Piatkus, pp91-92.
11 High Level Panel of Experts on Food Security and Nutrition. (2017) Sustainable forestry for food security and nutrition, Rome, Italy: Food and Agriculture Organization of the United Nations (FAO), summary p4, available at www.cifor.org/library/6549; A forest is defined by the FAO as land having trees over 5m tall, with at least 10% canopy cover and an area of more than 0.5 hectares; see FAO (2016) Global Forest Resources Assessment: How Are the World’s Forests Changing, Rome: FAO.
12 Kanninen M, Murdiyarso D, Seymour F, et al. (2007) Do Trees Grow on Money? The Implications of Deforestation Research for Policies to Promote REDD, Situ Gede, Indonesia: Centre for International Forestry Research.
13 Willis KJ. (2017) State of the World’s Plants 2017, Kew: Royal Botanic Gardens.
14 Spathelf P, Van Der Maaten E, Van Der Maaten-Theunissen M, et al. (2014) Climate change impacts in European forests: The expert views of local observers. Ann For Sci 71: 131-137.
15 Rothamsted Research. (2005) Climate Change and Land Management, Harpenden: Rothamsted Research.
16 Broadmeadow MSJ, Ray D and Samuel CJA. (2005) Climate change and the future for broadleaved tree species in Britain. Forestry 78: 145-161.
17 Willis (2017) p22.
18 Jenkins M, Timoshyna A and Cornthwaite M. (2018) Wild at Home: Exploring the Global Harvest, Trade and Use of Wild Plant Ingredients, Cambridge: Traffic International, available at www.traffic.org/site/assets/files/7339/wild-at-home.pdf (accessed 29 June 2019).
19 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Secretariat. (2018) Non-timber forest products: CITES implementation for medicinal plant species. Document submitted to the Seventieth Meeting of the Standing Committee, 1-5 October 2018. Available at: https://cites.org/sites/default/files/eng/com/sc/70/Inf/E-SC70-Inf-36.pdf (accessed 7 March 2019).
20 FAO. (2018) The State of the World’s Forests, 2018 – Forest Pathways to Sustainable Development, Rome: FAO, p500; Laird SA, McLain R and Wynberg RP. (eds) (2010) Wild Product Governance: Finding Policies that Work for Non-timber Forest Products, London: Earthscan.
21 Schippmann U, Leaman DJ and Cunningham AB. (2002) Impact of cultivation and gathering of medicinal plants on biodiversity: global trends and issues. Biodiversity and the Ecosystem Approach in Agriculture, Forestry and Fisheries. Satellite event on the occasion of the Ninth Regular Session of the Commission on Genetic Resources for Food and Agriculture. Rome, 12-13 October 2002, p8; Shackleton CM and Pandey AK. (2014) Positioning non-timber forest products on the development agenda. For Policy Econ 38: 1-7.
22 Schippmann et al. (2002).
23 Vines G and Behrens J. (2004) Herbal Harvests with a Future: Towards Sustainable Sources for Medicinal Plants, Salisbury: Plantlife International.
24 Rao MR, Palada MC and Becker BN. (2004) Medicinal and aromatic plants in agroforestry systems. Agroforestry Systems 61-62: 107-122. For organisations related to agroforestry in USA and Europe see Appendix 6(A).
25 Vance NC and Thomas J. (October 1997) Special Forest Products: Biodiversity Meets the Marketplace, Washington DC: US Department of Agriculture, Forest Service.
26 Davis JM. (2012) Assisting farmers to produce high-quality medicinal herbs. HortScience 47: 976-978.
27 Chamberlain JL, Bush R and Hammett AL. (1998) Non-timber forest products: The other forest products. Forest Products Journal 48: 10-19; Milliken W and Bridgewater S. (2001) Flora Celtica: Sustainable Development of Scottish Plants, Edinburgh: Edinburgh Development Consultants/ Royal Botanic Garden/ Scottish Executive Central Research Unit.
28 van Bemmel K, Grimm K, van der Maas S, et al. (2017) The Potential of Permaculture Principles in the Agrifood Transition, Den Bosch, The Netherlands: HAS Research Group: New Business Models for Agrifood Transition. For organisations related to permaculture see Appendix 6(E).
29 Booker AAA, Frommenwiler DA, Scotti F, et al. (2018) St John’s wort (Hypericum perforatum) products – an assessment of their authenticity and quality. Phytomedicine 40: 158-164.
30 A list of products granted traditional herbal registration in the UK is at www.gov.uk/government/publications/herbal-medicines-granted-a-traditional-herbal-registration-thr (accessed 25 July 2019).
31 Newmaster SG, Grguric M, Shanmughanandhan D, et al. (2013) DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine 11: 222.
32 Palhares R, Drummond M, dos Santos Alves Figueiredo Brasil B, et al. (2015) Medicinal plants recommended by the World Health Organization: DNA barcode identification associated with chemical analyses guarantees their quality. PLoS One 10: e0127866.
33 Lange D. (2006) International trade in medicinal and aromatic plants: Actors, volumes and commodities. In: Bogers RJ, Craker LE and Lange D (eds) Medicinal and Aromatic Plants, Netherlands: Springer, pp155-170.
34 Jenkins et al. (2018).
35 The Standard International Trade Classification, first established in 1950, classifies most medicinal and aromatic plants as ‘Plants and parts of plants (including seeds and fruits) of a kind used primarily in perfumery, in pharmacy, or for insecticidal, fungicidal or similar purposes, fresh or dried, whether or not cut, crushed or powdered’. The code used is 292.4. The European Union uses another more recently introduced system of ‘Harmonized Commodity Description and Coding’. The code used is HS 1211.
36 Bodeker G, Ong CK, Grundy C, et al. (eds) (2005) WHO Global Atlas of Traditional, Complementary and Alternative Medicine, Kobe, Japan: WHO Centre for Health and Development.
37 International Trade Center (ITC). (March 2017) Market Insider for Medicinal Plants, Geneva, Switzerland: ITC.
38 Ressmann AK, Kremsmayr T, Gaertner P, et al. (2017) Toward a benign strategy for the manufacturing of betulinic acid. Green Chem 19: 1014-1022.
39 Smith T, Kawa K, Eckl V, et al. (2018) Herbal supplement sales in US increased 8.5% in 2017, topping $8 billion. HerbalGram 119: 62-71.
40 Grand View Research. (2019) Organic personal care market size, share and trends analysis report, www.grandviewresearch.com/industry-analysis/organic-personal-care-market (accessed 29 June 2019).
41 Karjalainen E, Sarjala T and Raitio H. (2010) Promoting human health through forests: Overview and major challenges. Environ Health Prev Med 15: 5.
42 Jenkins et al. (2018); Osemeobo GJ. (2005) Living on the forests: Women and household security in Nigeria. Small-scale Forest Economics, Management and Policy 4: 343-358.
43 Species at risk in Europe have been identified, Allen D, Bilz M, Leaman DJ, et al. (2014) European Red List of Medicinal Plants, Luxembourg: Publications Office of the European Union. For further sources of information see Appendix 6(B).
44 Schippmann et al. (2002) p10.
45 Self-help advice books have had a resurgence, for example see Wong J. (2009) Grow Your Own Drugs: Easy Recipes for Natural Remedies and Beauty Treats, London: Collins.
46 Smith et al. (2018).
47 Sustainability report for Pukka Herbs is at www.pukkaherbs.com/media/76571305/pukka-sustainability-report-2017.pdf; and for Weleda is at www.weleda.co.uk/content/files/pdfs/Weleda-Annual-Sustainability-Report2017.pdf (both accessed 19 July 2019).
48 The International Code of Botanical Nomenclature ensures that all plants are classified with the binomial system giving first the genus name and second the species name. The most up-to-date accepted list of binomial names is the Plant List found at www.theplantlist.org (accessed 29 June 2019).
49 The Plants for a Future database is at www.pfaf.org (accessed 29 June 2019).
50 PubMed is hosted at www.ncbi.nlm.nih.gov/pubmed and provides access to abstracts of published scientific research studies.