Chapter 1

The Medicinal Uses of Trees and Shrubs

This chapter underpins the important role of medicinal trees and shrubs in the wider context of herbal medicine. Many of these woody healing plants are in use today as part of traditional systems around the world. This chapter provides an overview of research into traditions of use of herbal medicines, particularly trees and shrubs, as well as the practices of herbal medicine today. The study of individual plant constituents has increased our understanding of the actual and potential uses of plants in health and disease. You may already have come to know plants around you through cultivation or spending time out with nature, and will readily recognise aromas, colours and tastes that reflect some of a plant’s constituents. Here, the medicinal actions of key herbal constituents are briefly outlined with indications of medicinal plant uses, with examples in preventative health, antibiotics, cancer and ageing treatments. There is considerable evidence for the wider health benefits of trees in the environment, contributing to both mental and physical health. Finally, I look at how some of the actions of plant constituents may be useful in aid for common ailments. The chapter ends with a quick access listing providing a guide to 40 trees and shrubs which are described in much more detail in Part 2 of this book.

Medicinal plants and traditional uses

An incredible range of medicinal plants can be found in many different contexts. From gardens of all kinds: cottage, botanic, hospice and parks, to agricultural, forestry and wilder environments: fields, marshes, moors, mountains and woods, there are plants at every level from ground to overstorey that have traditional uses for health. Many of these plants are trees and shrubs. For the purpose of this book, a tree is generally a plant with a woody stem having branches at some distance from the ground whereas a shrub has multiple stems arising from the ground and is smaller than a tree.1 Many of these healing plants can now be identified as containing key constituents which often explain not only some of their traditionally observed actions, but also indicate further possibilities for use.²

Quercus robur (and related species) has astringent tannin-rich bark

Some examples of past use of tree preparations for medicinal purposes can give an idea of the range of complaints that were treated. Externally, alder (Alnus glutinosa) bark was used as a decoction for bathing swellings and was traditionally used for sore throat and ague. Few folklore records are reported of the use of this tree, although the ripe cones were drunk in tea for gout on the Somerset-Dorset border, and the leaves were crushed and laid on burns in Norfolk.³ Another tree, elder (Sambucus nigra), provided leaves that when bruised could be rubbed on the skin or worn in a hat to repel flies, and they were traditionally used to make a ‘green ointment’ used for piles, tumours and swellings. A longstanding remedy was oak (Quercus robur or ­petraea). According to Richard Elkes in 1651, the advice given to an old soldier was to boil oak bark for stomach upsets:

Carrie in your Knap-sacke a piece of steele to heat red hot, and quench it in your beer, water, or milke, and as you travel gather the leaves and barke of the Oake, and the leaves of the black-Thorn, a bagge of Salt and Oatmeale, that if the Flux should take you, you might helpe your selfe.⁴

Oak bark does have some antiseptic effect. These remedies could have been effective although we now know that the particular type of tannin found in oak bark means that it should not be used internally for long periods.

Of course, the use of plants for healing purposes is nothing new, since the medical uses of plants have been explored in many traditions throughout the world for centuries. Ethnobotany is the systematic study of traditional knowledge and customs of people and their relationships with plants. Started as a discipline in the later nineteenth century, ethnobotany began by collecting data about plant uses, particularly in countries of northern and southern Americas, Asia⁵ and Africa.⁶ Later studies were carried out in Europe,⁷ and in the twenty-first century the focus has turned towards reaping ideas for pharmaceutical drug discovery rather than recording traditional practices.⁸ Ethnobotanical studies provide us with examples of the kinds of preparations used by indigenous peoples, but some of these preparation methods may have fallen out of use. For example, the use of fire on tree parts such as bark, leaves, flowers and cones, is not often seen for medicinal purposes: the Inuktitut of Canada once burned and inhaled the smoke of alder (Alnus viridis) to treat rheumatism and as an insecticide against mosquitoes, the Antrim of Ireland inhaled the smoke and smouldering twigs of ash (Fraxinus excelsior) as a worm treatment, and in the Ubage Valley of France, elder (Sambucus nigra) flowers were used to provide smoke for fumigating eye problems.⁹

New plant introductions

There are also many examples of introduced plants, including shrubs and trees, that have medicinal value. In the past, knowledge about plants for medicinal use travelled widely across continents and many plants, including trees, were transported to new areas as exotic introductions.¹⁰ For example, plants brought to the UK from Europe and Asia, some attributed to the Romans, included sweet chestnut, walnut and mulberry.¹¹ By the end of the sixteenth century,¹² there were over 100 foreign trees and shrubs in cultivation in the UK, including some North American introductions such as arbor vitae (Thuja occidentalis). Many more introductions were made in the seventeenth century, when botanic gardens were being established in the UK including Oxford (1621), Chelsea Physic Garden (1674) and Edinburgh (1680). In the nineteenth and twentieth centuries, more plants were collected from China, Japan, South America and the Himalayas.¹³ Many introduced plants, once claimed to provide medicinal actions, nowadays are more highly regarded for their ornamental value.

Herbal medicine today – practitioners and remedies

Worldwide, there are numerous traditional systems of healthcare still in existence, and the World Health Organization (WHO) has recognised the importance of such provision, whether known as traditional medicine or complementary medicine. Four development objectives for traditional medicine have been identified by the WHO:

• to develop policy to integrate traditional medicine,
• to promote the knowledge base supporting safety, efficacy and quality,
• to increase availability and affordability,
• to promote rational therapeutic use of traditional medicine.

In 2013, the progress in achieving these objectives was reviewed, and the WHO sought more action from member states.¹⁴ Despite these efforts, recognition of traditional medicine practitioners continues to vary considerably throughout the world. While traditional Chinese medicine and Ayurvedic practitioners are well integrated and supported to some extent within national medical systems, there are many barriers to traditional practices in other countries of Europe and North America. In these Western contexts where ­evidence-based medicine holds sway, the use of traditional or complementary medicine approaches is largely denigrated even where there is research evidence for positive outcomes. Clinical complementary medicine practitioners have formed professional bodies and sought to provide self-regulation based on training, standards and ethical guidelines.¹⁵ Practitioners of herbal medicine are trained to use holistic approaches to treatment alongside knowledge of orthodox clinical approaches and the pharmacological actions of plants. Rather than providing over-the-counter remedies and symptomatic treatment, the clinical herbal practitioner takes a detailed case history and aims to identify underlying issues that may be treated with combinations of medicinal herbs and diet.

The use of herbal remedies is dependent on knowledge about plants, which is usually formulated in herbal monographs providing details of constituents, actions, preparations and indications alongside research and traditional uses. There is a process for recognition in the European Union of herbal remedies with evidence of longstanding traditional use, and monographs are compiled. In the US, Europe and UK there have been extensive efforts to establish accurate and detailed monographs to help improve standards of supplies of herbs. Safety and efficacy issues, rightly, have come to the fore and handbooks with pharmacopoeia standards help to clarify any possibilities of adverse effects or other considerations.¹⁶ However, where herbal monographs are based solely on ‘evidence-based’ studies, they do not always benefit from associated historical information such as traditional experience with safe forms of use and dosage.

Synergy and the approach of herbal medicine

Many research studies into the actions of medicinal plants continue to try to isolate single active constituents. But some researchers have pointed out the advantages of plant combinations and whole plant extracts.¹⁷ Containing many constituents, the whole plant extract shows synergy with enhancements of activity enabled by different constituents. Synergistic effects can make whole plant extracts more effective, for example by enabling greater absorption. Some lipophilic plant constituents readily dissolve in fats or oils and are able to cross cell walls to produce antimicrobial effects. Other constituents, such as flavonoids, are able to inhibit DNA synthesis or energy metabolism in microbial cells and further undermine the spread of disease.¹⁸ A study on treatments for dry eye found that natural extracts of bilberry fruit were more effective than purified anthocyanins: the plant constituents were acting together synergistically for greater effect.¹⁹ However, research into herbal medicines continues to suffer from lack of support. Reviews may point towards efficacy but call for more studies, and lack of funding prevents further detailed investigation unless a commercial prospect is seen.

Rosemary (Rosmarinus officinalis) contains antibacterial essential oils

Using plants in health and disease

Preventative health care and plants

Plants may be considered not only for treating disease but are also key contributors to many aspects of preventative health. The benefits of plant-rich diets are widely recognised. For example, berry fruits are often considered as ‘superfoods’ due to their high content of vitamins, fibre and phenolic compounds. The bright colours of many berries, from blackberries and raspberries (Rubus species) to bilberries (Vaccinium species) and chokeberries (Aronia melanocarpa), blackcurrants (Ribes nigrum) and elderberries (Sambucus nigra) are due to anthocyanins. Studies show that the leaves of these plants are also rich in these phenolic constituents, and these by-products could be used rather than wasted when berries are harvested.²⁰ Not only can individual plants contribute to health but also the diverse range of plant species helps to promote health. The existence of forests has been shown to contribute to child health overall, through beneficial effects on children’s diets. When forest access and children’s diet were reviewed in 27 developing countries, the greatest dietary diversity was found for households living within 3km of a forested area with 40% tree cover. This diversity was significant in providing micronutrients such as vitamin A and iron, showing that forest conservation can have a direct impact on health and mortality.²¹

Plants that fight bacteria

Many of the trees and shrubs mentioned in this book have powerful antibacterial effects. Coniferous trees such as the Douglas fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris) and juniper (Juniperus com­munis) all contain antiseptic essential oils. Other aromatic trees include eucalyptus (Eucalyptus species), sweet bay (Laurus nobilis) and sweet gum (Liquidambar styraciflua). A number of woody shrubs considered as ornamentals are also useful in this respect, having antiseptic properties, such as forsythia (Forsythia suspensa) and myrtle (Myrtus communis). Some bacterial challenges to human health have outstripped the resources available and threaten catastrophe, such as the spread of methicillin-resistant Staphylococcus aureus (MRSA), which appears to defy modern antibiotics. It is possible that new treatments may be found from natural sources, such as the use of isoflavonoids from plants as anti­microbials.²² Other studies of extracts of common plants, such as nettle (Urtica dioica) and rosemary (Rosmarinus officinalis), also show high antibacterial potential.²³

Fresh clippings of yew (Taxus baccata) are a source of taxol

Using plants to beat cancer

Cancer accounted for 8.8m deaths globally in 2015.²⁴ Natural products have attracted attention as pos­sible aides to cancer treatment, either in direct use or as leads for further drug development. Extracts from the yew (Taxus species) are used in a range of cancers. Paclitaxel (known in commerce as taxol) was originally extracted from the bark of the Pacific yew (Taxus brevifolia) though it can now be made from precursors in the needles of yew family members such as common yew (T. baccata). This drug targets β tubulin to prevent proper mitotic spindle assembly, so causing the death of replicating cancer cells. Various formulations have been developed to direct the paclitaxel in the body to a tumour location, and further synthetic derivatives such as docetaxel and cabazitaxel have now been developed for clinical use.²⁵ A range of other plant constituents are being investigated for possible use in cancer treatments. One example is betulinic acid, a triterpene which can be obtained from birch (Betula pendula) bark. Betulinic acid appears to be cytotoxic in a wide range of cancer types; the mechanism of action includes causing mitochondrial collapse in cells and other effects including limiting the blood supply and speed of metastasis. Syn­er­gistic effects with other anticancer drugs have also been found. Betulinic acid is slightly soluble in water, and research is under way to find methods of use or derivatives which are readily available to the body.²⁶ Another example, berberine, has also been suggested to have considerable potential in cancer treatments. Berberine is found in plants such as barberry (Berberis vulgaris) and Oregon grape root (Berberis aquifolium). It has been shown that berberine exhibits preferential selectivity for human pancreatic cancer cells compared to other cells.²⁷

Alder buckthorn (Frangula alnus) contains anthraquinones such as emodin

Ageing, anti-oxidants and healing plants

Anti-oxidant and anti-inflammatory effects are widespread in plant extracts, and can contribute to slowing the effects of the ageing process. In particular, research is being carried out to develop ways to use plants to treat some of the diseases associated with neurological ageing. For example, Alzheimer’s disease is known to involve abnormal clumping together of Tau proteins in a way that disrupts the neurons in the brain. These proteins collect together to form paired helical filaments which are a hallmark of Alzheimer’s disease. One study looked at 200,000 compounds to see if any would stop or alter this aggregation. Using various tests the study showed that several types of plant anthraquinones were able to inhibit the formation of the paired helical filaments and these included emodin, daunorubicin and adriamycin.²⁸ Emodin is a widely found constituent in plants as diverse as alder (Alnus glutinosa), alder buckthorn (Frangula alnus) and rhubarb (Rheum officinale).²⁹

Ginkgo (Ginkgo biloba) can tolerate urban pollution

Trees and health in the environment

Green infrastructure

Wider ecosystems and human health are related in many ways, and biodiversity, in forests and elsewhere, remains crucial for the health of a large proportion of the world population.³⁰ Trees are a significant component of the ‘green infrastructure’ of parks, gardens, forests, farmland and open spaces, ‘an interconnected network of green space that conserves natural ecosystem values and functions and provides associated benefits to human populations’.³¹ Ecosystem services have been identified in four categories to which trees contribute:

• provisioning (food, medicine and water),
• regulating (climate, flood control, soil fertility, pollination, disease modulation),
• cultural (recreation, spiritual and mental health)
• supporting (soil formation, nutrient and water cycling).

Trees are good for the urban environment too. This was recognised by John Evelyn in earlier times, writing about trees in 1661. He wrote of how ‘a mass of sweet smelling trees, bushes and plants would be planted to surround and vivify London’.³² Today, we understand better the mechanisms of health improvement in urban areas through trees which include shading in heat, reduction of ultraviolet radiation, reduction of wind speed, reduction of air pollution, encouraging physical activity in green space, and reduction of stress and noise levels.³³

The benefits of trees in urban areas

In the urban context of Toronto, people living in neighbourhoods with a higher density of street trees reported significantly fewer cardio-metabolic conditions (hypertension, high blood sugar, obesity, high cholesterol, heart disease, stroke and diabetes).³⁴ In real terms, after adjusting for income and other factors, this study showed that 10 more trees in a city block equated to being seven years younger, and the equivalent of $10,000 per annum extra income. Overall, urban trees provide more benefits than cost in planting and maintenance, yet the need for these trees is not readily understood.

Sweet gum trees form a living cathedral in Porto, Portugal

Forest bathing

A forest environment can provide measurable benefits for individual health – ranging from speedier physical recovery from illness to improvement of mental health, reductions of stress and mortality to improving outcomes in pregnancy.³⁵ Shinrin-yoku or ‘experiencing the forest atmosphere’ has become popular for its therapeutic effect: physical changes have been identified, such as an improved immune system arising from forest visits.³⁶ Forest bathing or walking in woods research studies have shown recognisable health benefits for depression and hypertension.³⁷ A randomised controlled trial with women aged over 60 years old in Korea showed that just one hour of walking around a forested area improved arterial stiffness and pulmonary function.³⁸ A review of 20 trials found that both diastolic and systolic blood pressure in the forest environment were significantly lower than in a non-forest environment, particularly in older people.³⁹ Further reviews are needed to confirm the positive effects of forest therapy in circulatory conditions, inflammation, stress, anxiety and depression.⁴⁰ In addition to supporting physical health, trees in formal arrangements can provide cathedral-like spaces for reflection and restoration of mental health.

Trees and spiritual regeneration

Whilst we know that trees can contribute to physical and mental health, there is also an unescapable aspect of spirituality in the ways that we relate to them and nature. In some cultures, there are inbuilt connections to the land which provide an ongoing link with nature over generations. A great example of the living link with trees and forests can be seen in the ‘hytte’ of Norwegian culture. In the following Case Study you can see an example of this in practice.

case study: Forest bathing and deep relaxation in Norway

Name: Karen With is a hardworking educator and celebrant based in south west England. She is half-­Norwegian, and has access to a small cabin or ‘hytte’ in a wooded river valley, 20km from Oslo.

Location: Kjaglidalen, Norway, about 30km from Oslo

Activity: Karen says “Wider health benefits from trees include immersion/forest bathing. Central to Norwegian lives is the ‘hytte’, either by the sea, in the mountains or in the forest. My whole life has involved temporarily living immersed in nature. Seeing the natural world through these cultural lenses has enabled me to tune in and rejuvenate. Through reconnecting with self and forming intimate relationship with certain trees, the layers fall away and deep relaxation occurs. Living a more simple life off-grid is regenerating and soul-­enriching and such a tonic! A deeper connection occurs and the benefits of foraging and managing fuel for heating connects me to the cycle of life. What a gift such places/times are in our fragmented world, spending time in forest retreat offers wellbeing as well as a refreshing sense of renewal, whilst relating to the trees.”

Key point: Trees are an integral part of cultural engagement with nature, contributing to rejuvenation, reconnection and renewal.

A forest hytte for relaxation and renewal in Norway

* * *

Phytochemistry and plant constituents

Phytochemistry refers to the study of chemical constituents of plants, and often there are hundreds of chemicals involved in just one plant. Many key active constituents of medicinal plants are secondary metabolites, not essential to plant life but useful in defence, protecting from predators and environmental damage.⁴¹ The three main groups of secondary metabolites are phenols, terpenoids and alkaloids, and examples are shown in the table below.⁴² Many plant constituents can be fitted into more than one of the categories shown. Other significant groups of plant constituents include saponins, which produce a soap-like foam when shaken with water, and polysaccharides or sugar-like complexes that can be found as gums, mucilages and resins.

Examples of secondary metabolites in medicinal plants

Plant examples	Key constituents	Actions and possible effects
Oak (Quercus robur) Agrimony (Agrimonia eupatoria) Avens (Geum urbanum)	Polyphenolic tannins	External astringent drying effect to aid the healing of spots and wounds Internal soothing of sore throats
St John’s wort (Hypericum perforatum) Bilberry (Vaccinium species) Blackberry (Rubus fruticosus) Hawthorn (Crataegus monogyna)	Phenolic flavones and flavonoids e.g. quercitin, genistein, myricetin Also anthocyanins, widely found blue, purple or red pigments in fruits	Have anti-inflammatory effects and strengthen the circulatory system, helping to repair connective tissue and blood vessels
Alder buckthorn (Frangula alnus) Curled dock (Rumex crispus)	Anthraquinones	Laxative due to stimulation of intestinal muscle
Birch (Betula pendula) Pine (Pinus sylvestris) Snow gum (Eucalyptus pauciflora) Black peppermint (Mentha x piperita vulgaris)	Monoterpenes e.g. geraniol, limonene, menthol, camphor characteristic of aromatic volatile essential oils	Antiseptic and support the immune system Some terpenes are calming for digestion
Mugwort (Artemisia vulgaris) Myrtle (Myrtus communis)	Sesquiterpenes e.g. farnesol, artemisinin	Antimicrobial effects Can affect the nervous system
Barberry (Berberis vulgaris) Oregon grape root (Berberis aquifolium) Bittersweet (Solanum dulcamara)	Alkaloids e.g. ephedrine, berberine	Affect the nervous system, may be stimulant or depressant depending on plant
Marsh mallow (Althaea officinalis)	Mucilages, polysaccharides	Soothe and reduce inflammation
Liquorice (Glycyrrhiza glabra)	Saponins or soap-like substances	Can reduce inflammation and are somewhat emetic and used as expectorants

Phenols

Phenolic plant constituents contain aromatic hydrocarbon rings, such as the polyphenolic molecules known as tannins which are astringent and drying in their actions. One of the earliest and most well-known phenolic plant constituents to be chemically identified is salicin, a phenolic glycoside found in the leaves and bark of willow (Salix species) trees.⁴³ Willow bark has long been used to relieve fever, having anti-inflammatory and painkilling effects, a predecessor to commercial aspirin, acetylsalicylic acid, developed in the twentieth century as less irritating to the stomach.⁴⁴ A Cochrane systematic review assessed the effectiveness of herbal medicines for low back pain, including white willow (Salix alba) bark and found evidence of improvement.⁴⁵ Phenolic compounds can have other effects including anti-oxidant activity as well as antibacterial effects. A survey of phytoextracts of relevance in skin care, with emphasis on phenolic acids and flavonoids, found that many could be derived from tree barks including sweet chestnut (Castanea sativa), sea buckthorn (Elaeagnus rhamnoides), mulberry (Morus alba) and pomegranate (Punica granatum).⁴⁶ Extracts from a range of tree barks were evaluated for their radical-scavenging activity, and showed antibacterial effects on gram-positive Staphylococcus species, as well as other benefits to the skin.⁴⁷ Not only are new constituents constantly being identified, but also new uses have been proposed for parts of trees previously considered as waste, such as the knots in timber discarded in processing in forestry. A new polyphenolic lignan and stilbenoid mixture extracted from the knots of Scots pine (Pinus sylvestris) has shown promise for use in prostate cancer.⁴⁸

White willow (Salix alba) leaves and bark are rich in phenols with anti-inflammatory actions

Terpenes

Terpenes are unsaturated hydrocarbons and are widespread in plants, giving rise to terpenoids (also known as isoprenoids) in plant extracts, including the chemicals producing the aroma of essential oils. We are familiar with many of these essential oils in aromatic herbs such as mints, as well as sweet-smelling citrus and pine trees. Terpenes occur in various subclasses such as mono-terpenes, sesquiterpenes and diterpenes, and have important anti-inflammatory, anti-oxidant, antiviral and antibacterial properties. Artemisin is a sesquiterpene lactone used in malaria treatment, and it was originally derived from sweet wormwood (Artemisia annua) in the daisy family (Asteraceae). Terpenes can form the basis for steroid hormones, and some triterpenes are created by plants for defence against insects. These triterpenoid chemicals can mimic the hormones used by insect plant-eaters, and this disrupts moulting processes, so that their metabolism is seriously affected.⁴⁹

Douglas fir (Pseudotsuga menziesii) bark essential oils contain terpenes

Alkaloids

Alkaloids are best known as the nitrogen-­containing plant constituents that affect the nervous system, inclu­ding some important opiate drugs in the poppy or Papaveraceae family, and other active chemicals such as caffeine from coffee (Caffea arabica). Used with care, the alkaloids can have positive effects, and efforts to extract alkaloids from forestry residues are of continuing commercial interest.⁵⁰ Taxol, or paclitaxel, is an alkaloid derived from yew trees, or Taxus species. Some significant plant-based alkaloids are reported in the State of the World’s Plants 2017, including an extract of the alkaloid galantamine from snowdrops (Galanthus species) and daffodils (Narcissus species), which is used in treating Alzheimer’s disease.⁵¹ Berberine, also mentioned earlier, is an alkaloid found in many plants including the barberry and the ornamental Oregon grape (Berberis species), readily recognised by its bright yellow colour. The effects of this alkaloid include lowering of blood cholesterol and glucose, making it of interest in a range of metabolic disorders.⁵²

Oregon grape (Berberis aquifolium) is rich in berberine, an alkaloid

Phytochemistry in action

Using plants in common ailments

Many plant constituents have desirable actions in providing immediate aid for common ailments (see table below). Knowledge of the phytochemistry of plants may be helpful in explaining the actions of individual plants, but is not essential for using them. If treatment of acute conditions is given then it must always be followed through, for example by keeping the person warm, accompanying them home, checking on how they are over the following 24 hours, and referring to a qualified clinical practitioner if symptoms do not resolve. Acute treatment provides short-term relief and encourages healing: it does not take the place of a full consultation with a medical practitioner or professional medical herbalist who will take a detailed case history in which medical history, medications, systems, diet etc. are considered. Immediate aid for minor complaints with herbal remedies may involve herbs offering anodyne pain relief. Further action may be anti-inflammatory providing reduction of swelling, redness and heat or antispasmodic to relax muscles and reduce tension. Other helpful actions would be to soothe irritation (demulcent or emollient) and also to provide some antiseptic or antimicrobial effect. As a general rule when dealing with cuts, bites, bruises, first make sure the area is clean. However, it is important to know your plants! Always seek advice from a qualified clinical practitioner if symptoms persist! Some conditions should always be referred for medical help, and these include trauma, severe bleeding, breathing difficulties, very high temperature (especially in children), eye problems and severe allergic response.

Herbal actions and some common ailments

Herbal action	Example of plant
Astringent – an action of plants that are rich in tannins which reduce secretions. The effect of the tannins is styptic, ideal for stopping blood flow.	Bramble (Rubus fruticosus) has both leaves and roots with astringent effects, used in folklore for many skin disorders from spots, sores to burns and boils. Yarrow (Achillea millefolium) is an example of a vulnerary herb that promotes wound repair. The effect of stopping a nosebleed was traditionally achieved by rolling up and inserting a leaf into the nose.
Anti-inflammatory – many plants contain compounds which have an anti-inflammatory action.	Meadowsweet (Filipendula ulmaria) contains natural aspirin-like chemicals in the flowering tops and can be used in a tea to reduce pain. Willow species (Salix alba, S. diaphnoides) contain substantial tannin and salicin in the bark and this can be used fresh or dried.
Antiseptic – an antiseptic action is especially found in plants containing aromatic oils or volatile ingredients.	Pine (Pinus species) and larch (Pinus larix) are sources of resin exuding from the bark, and this can be distilled to produce a powerful antiseptic essential oil. Wild garlic (Allium ursinum) contains pungent, volatile ingredients rich in sulphur, and the juice of the plant can be diluted with water and applied direct.
Antispasmodic – the antispas­modic action provides a reduction of pain and tension and can be a result of constituents such as alkaloids which relax muscles.	Cherry (Prunus species) bark has some antispasmodic effect for the relief of dry coughs. Cramp bark (Viburnum opulus) contains the bitter glucoside viburnine as well as valerianic acid and can be taken in a decoction for all kinds of cramps and spasms.

Medicinal plants to grow and use today

There are thousands of plants which have medicinal uses, far too many to list here. The many traditional uses of medicinal plants, including trees and shrubs, are being revealed through research evidence, though much more remains to be done in terms of clinical studies. Medicinal trees and shrubs provide a win-win outcome, since not only can they supply complex and efficacious remedies but they also help to improve the environment. In the following tables, you can see a quick access list of the 40 trees and shrubs which are fully detailed in the Part 2 Directory in this book. These trees and shrubs have been selected to provide a sample for possible inclusion in a medicinal forest garden. Listed alphabetically by common name, each plant is also identified by its Latin species name. The parts used with sample preparations and indications are given in Table A. In Table B cultivation details are provided for each plant including likely maximum height, climate zone, and soil and light preferences. If you turn to Appendix 3 you can see a further alphabetical list of 50 herbaceous plants summarising cultivation details and therapeutic uses, that may be grown and used alongside medicinal trees and shrubs.

Quick access listing of 40 trees and shrubs in Part 2 Directory

Table A: Parts used, sample indications and preparations

Common name Latin name	Parts used	Sample indications	Sample preparations
Alder buckthorn Frangula alnus	Bark, berries	Constipation	Powder, tincture
Arbor vitae Thuja occidentalis	Leafy twigs	Colds and flu, warts	Infusion, tincture
Ash Fraxinus excelsior	Bark, leaves, seeds	Arthritis, viral infections	Infusion, poultice, powder
Bilberry Vaccinium myrtillus	Leaves, fruit	Poor circulation, cystitis, high blood fats	Infusion, tincture
Bird cherry Prunus padus	Bark, fruit stalks, resin	Dry cough, cystitis	Decoction, syrup, tincture
Black chokeberry Aronia melanocarpa	Fruit, leaf	Respiratory infections	Fruit leather, infusion, syrup
Blackcurrant Ribes nigrum	Leaves, fruit	Sore throat, colds, flu, cystitis, stress	Gargle, glycerite, infusion, tincture
Black mulberry Morus nigra	Leaves, fruit	Lowering blood sugars, colds, sore throat	Infusion, tincture, gargle
Broom Cytisus scoparius	Flowering shoots	Hypotension, fluid retention, arthritis	Infusion, tincture, decoction
Chaste tree Vitex agnus-castus	Leaves, fruit	Premenstrual tension, menopause	Infusion, inhalation, tincture
Cramp bark Viburnum opulus	Bark	Painful periods, threatened miscarriage, poor circulation	Powder, tincture
Dog rose Rosa canina	Leaves, flowers, fruit	Infections, cardiovascular and degenerative diseases	Decoction, infusion, syrup
Douglas fir Pseudotsuga menziesii	Leaves, bark, resin	Coughs, colds, sore throats	Hydrosol, inhalation, infusion
Elder Sambucus nigra	Flowers, fruit	Colds and flu	Infusion, syrup, tincture, vinegar
Fig Ficus carica	Fruit, leaves, latex	High cholesterol, skin diseases	Infusion
Forsythia Forsythia suspensa	Flowers, fruits, leaves	Sore throats and colds, urinary infection	Infusion, decoction, syrup
Fringe tree Chionanthus virginicus	Root and stem bark	Liver and gallbladder disorders	Tincture
Ginkgo Ginkgo biloba	Leaves, seeds	Poor circulation, anxiety, dementia	Infusion, powder, tincture
Hawthorn Crataegus monogyna	Flowers, leaves, fruits	Hypertension and anxiety	Infusion, tincture
Horse chestnut Aesculus hippocastanum	Seed, bark, leaf	Venous congestion, haemorrhoids, varicose veins	Venous congestion, haemorrhoids, varicose veins
Juniper Juniperus communis	Leaves, fruit	Cystitis, insect repellent	Infusion, tincture, lotion
Lily magnolia Magnolia liliiflora	Flowers, bark	Sinusitis	Decoction, infusion
Myrtle Myrtus communis	Leaves, fruit	Dyspepsia, cystitis, bronchitis, skin complaints	Hydrosol, infusion, tincture, gargle
Oregon grape Berberis aquifolium	Bark, roots	Skin disorders	Decoction, tincture
Prickly ash Zanthoxylum americanum	Leaves, bark, fruit	Leg cramps, rheumatism	Powder, tincture
Raspberry Rubus idaeus	Leaves, fruit	Painful periods, sore throat, childbirth	Gargle, infusion, tincture, vinegar
Red root Ceanothus americanus	Bark, leaves, root	Catarrh, sore throat and swollen glands	Infusion, tincture
Rosemary Rosmarinus officinalis	Leaves, flowers	Digestion, anxiety, memory	Hydrosol, infusion, tincture
Scots pine Pinus sylvestris	Leaves, bark, resin	Sinusitis, bronchitis, rheumatism	Infusion, inhalation, tincture
Sea buckthorn Elaeagnus rhamnoides	Fruit, leaves	Immune support	Infusion, juice, vinegar
Siberian ginseng Eleutherococcus senticosus	Bark, leaves, rhizomes	Exhaustion and stress	Infusion, powder, tincture
Silver birch Betula pendula	Bark, buds, leaves	Skin, rheumatism and urinary complaints	Infusion, glycerite, tincture
Small-leaved lime Tilia cordata	Flowers, leaves	Anxiety, insomnia, hypertension	Infusion, tincture
Snow gum Eucalyptus pauciflora	Bark, leaves	Coughs and colds	Hydrosol, infusion
Sweet bay Laurus nobilis	Leaves, fruit	Indigestion, colds	Hydrosol, infusion, lotion
Sweet chestnut Castanea sativa	Leaves and seeds	Coughs and colds	Infusion
Sweet gum Liquidambar styraciflua	Leaves, bark	Catarrh, coughs, colds	Infusion, lotion, syrup
Violet willow Salix daphnoides	Leaves, bark	Back and joint pain, headache, insomnia	Infusion, powder, gargle
Walnut Juglans regia	Bark, fruit, leaves	Constipation, eczema, dandruff, athlete’s foot	Infusion, tincture
Witch hazel Hamamelis virginiana	Leafy twigs, bark	Skin wounds and bites, acne, eczema, sprains	Decoction, distillation

Table B: Cultivation details

Common name Latin name	Potential height (m)	USDA climate zone	Soil preference	Sun and shade needs
Alder buckthorn Frangula alnus	5	3	Moist acid soil	Sun or light shade
Arbor vitae Thuja occidentalis	15	3	Moist well-drained soil	Sun or light shade
Ash Fraxinus excelsior	30	4	Most moist soils	Sun
Bilberry Vaccinium myrtillus	0.5	3	Well-drained acidic soil	Light shade
Bird cherry Prunus padus	16	3	Most moist soils	Sun or light shade
Black chokeberry Aronia melanocarpa	2	5a	Most soils	Sun or light shade
Blackcurrant Ribes nigrum	1.8	4	Moist acid soil	Sun or light shade
Black mulberry Morus nigra	10	5	Moist well-drained soil	Sun or light shade
Broom Cytisus scoparius	2	5	Dry acid soil	Sun or light shade
Chaste tree Vitex agnus-castus	3	8a	Dry or well-drained soils	Sun
Cramp bark Viburnum opulus	3	3	Most moist soils	Sun or light shade
Dog rose Rosa canina	3.5	3	Most well-drained soils	Sun
Douglas fir Pseudotsuga menziesii	60	5a	Moist well-drained acid soil	Sun
Elder Sambucus nigra	6	5	Most moist soils	Sun or light shade
Fig Ficus carica	6	8	Most soils	Sun
Forsythia Forsythia suspensa	3	5	Most soils	Sun or light shade
Fringe tree Chionanthus virginicus	5	5a	Rich moist soil	Sun or light shade
Ginkgo Ginkgo biloba	30	5a	Most soils	Sun
Hawthorn Crataegus monogyna	10	4	Any moist soil	Sun or light shade
Horse chestnut Aesculus hippocastanum	30	4	Most soils	Sun or light shade
Juniper Juniperus communis	9	4	Well-drained soil, slightly alkaline	Sun or light shade
Lily magnolia Magnolia liliiflora	4	7	Slightly acidic moist well-drained soil	Sun or light shade
Myrtle Myrtus communis	4.5	8	Dry or well-drained soil	Sun
Oregon grape Berberis aquifolium	3	5	Most well-drained soils	Shade
Prickly ash Zanthoxylum americanum	4	4	Moist well-drained soil especially alkaline soils	Sun or light shade
Raspberry Rubus idaeus	1.5	4	Moist acidic well-drained soil	Sun or light shade
Red root Ceanothus americanus	1	5	Poor dry soils	Sun or light shade
Rosemary Rosmarinus officinalis	2	6	Most soils including alkaline soils	Sun
Scots pine Pinus sylvestris	35	2	Light acidic soil	Sun or light shade
Sea buckthorn Elaeagnus rhamnoides	6	3	Most soils	Sun
Siberian ginseng Eleutherococcus senticosus	3	3	Rich, moist well-drained soil	Sun or light shade
Silver birch Betula pendula	25	2	Poor acid soils	Sun
Small-leaved lime Tilia cordata	30	3	Moist well-drained alkaline soils	Sun or light shade
Snow gum Eucalyptus pauciflora	12	8	Poor well-drained soil	Sun
Sweet bay Laurus nobilis	10	7	Most well-drained soils	Sun or light shade
Sweet chestnut Castanea sativa	30	5	Poor acid and well-drained soils	Sun
Sweet gum Liquidambar styraciflua	30	5	Well-drained acidic soil	Sun or light shade
Violet willow Salix daphnoides	6	5	Moist neutral to acid soil	Sun
Walnut Juglans regia	30	5	Well-drained soil	Sun
Witch hazel Hamamelis virginiana	5	5	Moist acid soil	Sun or light shade

Bramble or blackberry (Rubus fruticosus) is a highly astringent remedy

Conclusion

Understanding of the principal components of medicinal plants helps us to see how traditional uses may have been well justified, and can also provide the basis for extending to further possible uses. The potential discovery of commercially viable new drugs may be a driver for ongoing research. However, there is much to be gained from a holistic perspective appreciating the actions and synergy of constituents in whole plant extracts, and using them in an integrated way with other health-promoting elements of diet and lifestyle.

Learning about the medicinal actions of a plant from an expert herbal practitioner is a starting point for possible use. A good way to learn more about the traditional and modern uses of plants is to go on a local walk with a medical herbalist (see following Case Study). These walks allow you to learn about identification features which place each plant in a particular family or genus. Plants in the same family often have similar chemical compositions, so that familiarity with the uses of one plant can give clues as to the uses of a close relation. For further information there are courses available, from use of herbs for common ailments to professional practitioner training.53

case study: Herbal medicine in Alexandra Park food forest

Location: Glasgow, Scotland

Activity: Learning about medicinal plants is an activity offered at the Alexandra Park Food Forest. Based in the heart of a major city, the Glasgow food forest was planted as part of the Helping Britain Blossom project (now the Orchard Project). As Clem Sandison (shown here) explains, a free training course was the starting point for making the initial design, bringing together local residents to learn about growing fruit and help plant an orchard for the community. Various fruiting trees and shrubs have been planted in a forest garden design, which includes a wildflower meadow and beds with herbs. The trees and shrubs are establishing well in mulched areas on an open sloping site surrounded by a public park. Some further courses are offered including a popular course introducing medicinal plants, which is run by local medical herbalist Catriona Gibson. Catriona has completed a substantial training programme in botanical therapeutics with clinical training and is a registered medical herbalist with the National Institute of Medical Herbalists. She also has much expertise in foraging and can show people how to make seasonal food and medicine preparations.

Key point: Many benefits can be obtained from collaboration between forest gardens and herbal medicine practitioners to encourage interest in both edible and medicinal plants.

Info: www.facebook.com/AllyParkFoodForest

Contact: www.catrionagibson.co.uk/services

---

1 Thomas P. (2000) Trees: Their Natural History, Cambridge: Cambridge University Press, p1.

2 In the UK, many trees and shrubs were in use in medieval times for healing purposes; see Pollington S. (2008) Leechcraft: Early English Charms Plant Lore and Healing, Hockwold-cum-Wilton: Anglo-Saxon Books, pp493-507; Hooke D. (2013) Trees in Anglo-Saxon England: Literature, Lore and Landscape, Woodbridge: Boydell.

3 Allen DE and Hatfield G. (2004) Medicinal Plants in Folk Tradition: An Ethnobotany of Britain & Ireland, Portland, Oregon: Timber Press.

4 Elkes R. (1651) Approved Medicines of Little Cost, to Preserve Health and also to Cure those that are Sick Provided for the Souldiers Knap-sack and the Country Mans Closet, London: Printed for Robert Ibbitson and are to be sold by Tho: Vere at the Angel in the Old-Baily, p1.

5 For example: Hussain T, Rafay M, Manj IA, et al. (2017) Desert dwelling trees: Forage suitability and ethnobotany, Pakistan. J Biodivers Endanger Species 5: 194; Dolatkhahi M, Dolatkhahi A and Nejad JB. (2014) Ethnobotanical study of medicinal plants used in Arjan – Parishan protected area in Fars Province of Iran. Avicenna J Phytomed 4: 402-412.

6 For example in Tanzania: Luoga EJ, Witkowski ETF and Balkwill K. (2000) Differential utilization and ethnobotany of trees in Kitulanghalo Forest Reserve and surrounding communal lands, Eastern Tanzania. Economic Botany 54: 328-343.

7 For example in Austria: Vogl S, Picker P, Mihaly-Bison J, et al. (2013) Ethnopharmacological in vitro studies on Austria’s folk medicine: An unexplored lore in vitro anti-inflammatory activities of 71 Austrian traditional herbal drugs. J Ethnopharmacol 149: 750-771.

8 Newman D and Cragg G. (2007) Natural products as sources of new drugs over the last 25 years. J Nat Prod 70: 461-477.

9 Pennachio M, Jefferson LV and Havens K. (2010) Uses and Abuses of Plant-derived Smoke: Its Ethnobotany as Hallucinogen, Perfume, Incense, and Medicine, Oxford: Oxford University Press.

10 Chapter 2 of Conway (2001) provides a brief history of trees in medicine. A more detailed description of introductions is in Bean WJ. (1980) Trees and Shrubs Hardy in the British Isles, London: John Murray, pp3-21. For a detailed overview of the past use of individual plants see Grieve M. (1980) A Modern Herbal: The Medicinal, Culinary, Cosmetic and Economic Properties, Cultivation and Folklore of Herbs, Grasses, Fungi, Shrubs and Trees with All Their Modern Scientific Uses, 1931 edition, London: Penguin.

11 Bean WJ. (1976) Trees and Shrubs Hardy in the British Isles, Eighth edition, London: John Murray.

12 Based on Gerard J. (1633) The Herball or Generall Historie of Plantes, London: Printed by Adam Islip Ioice Norton and Richard Whitakers.

13 Bean (1980) p13.

14 World Health Organization (WHO). (2013) WHO Traditional Medicine Strategy: 2014-2023, Hong Kong: WHO.

15 See Appendix 6(C) for details of clinical herbal practitioner organisations.

16 Gardner Z and McGuffin M. (eds) (2013) American Herbal Products Association’s Botanical Safety Handbook, 2nd ed, Boca Raton: CRC Press; Mills S and Bone K. (2013) Principles and Practice of Phytotherapy, Edinburgh: Churchill Livingstone; Williamson E, Driver S and Baxter K. (2009) Stockley’s Herbal Medicines Interactions, London: Pharmaceutical Press; European Medicines Agency (April 2018) HMPC Monographs: Overview of recommendations for the uses of herbal medicinal products in the paediatric population, available at: www.ema.europa.eu/en/documents/other/hmpc-monographs-overview-recommendations-uses-herbal-medicinal-products-paediatric-population_en.pdf (accessed 13 March 2019).

17 Wagner H and Ulrich-Merzenich G. (2009) Synergy research: Approaching a new generation of phytopharmaceuticals. Phytomedicine 16: 97-110.

18 Sadowska B, Paszkiewicz M, Podsędek A, et al. (2014) Vaccinium myrtillus leaves and Frangula alnus bark derived extracts as potential antistaphylococcal agents. Acta Biochim Pol 61: 163-169.

19 Riva A, Togni S, Franceschi F, et al. (2017) The effect of a natural, standardized bilberry extract (Mirtoselect®) in dry eye: A randomized, double blinded, placebo-controlled trial. Eur Rev Med Pharmacol Sci 21: 2518-2525.

20 Ferlemi A and Lamari F. (2016) Berry leaves: An alternative source of bioactive natural products of nutritional and medicinal value. Anti-oxidants (Basel) 5: E17.

21 Rasolofoson R, Hanauer M, Pappinen A, et al. (2018) Effects of forests on children’s diets in developing countries: A cross-sectional study. Lancet Planet Health 2: S15.

22 For example, Abreu AC, Coqueiro A, Sultan AR, et al. (2017) Looking to nature for a new concept in antimicrobial treatments: Isoflavonoids from Cytisus striatus as antibiotic adjuvants against MRSA. Sci Rep 7: 3777.

23 Zenãoa S, Aires A, Dias C, et al. (2017) Antibacterial potential of Urtica dioica and Lavandula angustifolia extracts against methicillin resistant Staphylococcus aureus isolated from diabetic foot ulcers. J Herb Med 10: 53-58.

24 Seca AML and Pinto DCGA. (2018) Plant secondary metabolites as anticancer agents: Successes in clinical trials and therapeutic application. Int J Mol Sci 19: E263.

25 Walsh V and Goodman J. (2002) From Taxol to Taxol(R): The changing identities and ownership of an anti-cancer drug. Med Anthropol 21: 307-336.

26 Seca and Pinto (2018).

27 Pinto-Garcia L, Efferth T, Torres A, et al. (2010) Berberine inhibits cell growth and mediates caspase-independent cell death in human pancreatic cancer cells. Planta Med 76: 1155-1161.

28 Pickhardt M, Gazova Z, von Bergen M, et al. (2005) Anthraquinones inhibit tau aggregation and dissolve Alzheimer’s paired helical filaments in vitro and in cells. J Biol Chem 280: 3628-3635.

29 Dr Duke’s Phytochemical and Ethnobotanical Database, https://phytochem.nal.usda.gov/phytochem/search/list (accessed 13 February 2019).

30 Alves RRN and Rosa IML. (2007) Biodiversity, traditional medicine and public health: Where do they meet? J Ethnobiol Ethnomed 3: 14.

31 Coutts C and Hahn M. (2015) Green infrastructure, ecosystem services, and human health. Int J Environ Res Public Health 12: 9770; Rouquette JR and Holt AR. (2017) Research Report: The Benefits to People of Trees Outside Woods, Grantham: Woodland Trust/ Natural Capital Solutions.

32 Hickman C. (2013) Therapeutic Landscapes: A History of English Hospital Gardens Since 1800, Manchester: Manchester University Press, p14.

33 Sarajevs V. (2011) Health Benefits of Street Trees, Forest Research. Available at www.forestresearch.gov.uk/research/health-benefits-of-street-trees (accessed 30 June 2019).

34 Kardan O, Gozdyra P, Misic B, et al. (2015) Neighbourhood green space and health in a large urban centre. Sci Rep 5: 11610.

35 Coutts and Hahn (2015).

36 Li Q, Morimoto K, Koboyashi M., et al. (2008) Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. Int J Immunopathol Pharmacol 21: 117-127.

37 Mao GX, Cao YB, Lan XG, et al. (2012) Therapeutic effect of forest bathing on human hypertension in the elderly. J Cardiol 60: 495-502; also on reducing depression in an arboretum see Berman MG, Kross E, Krpan KM, et al. (2012) Interacting with nature improves cognition and affect for individuals with depression. J Affect Disord 140: 300-305.

38 Lee J-Y and Lee D-C. (2014) Cardiac and pulmonary benefits of forest walking versus city walking in elderly women: A randomised, controlled, open-label trial. Eur J Integr Med 6: 5-11.

39 Ideno Y, Hayashi K, Abe Y, et al. (2017) Blood pressure-lowering effect of Shinrin-yoku (Forest bathing): A systematic review and meta-analysis. BMC Complement Altern Med 17: 409.

40 Oh B, Lee KJ, Zaslawski C, et al. (2017) Health and well-being benefits of spending time in forests: Systematic review. Environ Health Prev Med 22: 71.

41 For a readable account of secondary metabolites see Tudge C. (2005) The Secret Life of Trees: How They Live and Why they Matter, London: Penguin, pp352-361; for the chemistry of natural products see Dewick PM. (2009) Medicinal Natural Products: A Biosynthetic Approach, Chichester: John Wiley; for a complete analysis of medicinal actions of plant constituents see Ganora L. (2008) Herbal Constituents: Foundations of Phytochemistry, Louisville, Colorado: Herbalchem Press.

42 Yang L, Wen K-S, Ruan X, et al. (2018) Response of plant secondary metabolites to environmental factors. Molecules 23: E762; Crawford M. (2015) Useful chemicals from trees. Agroforestry News 23: 24-39.

43 British Herbal Medicine Association (BHMA) Scientific Committee. (1983) British Herbal Pharmacopoeia, Bournemouth: BHMA, p184.

44 Meyrick W. (1790) The New Family Herbal: or Domestic Physician, Birmingham: Printed by T. Pearson; and sold by R. Baldwin, London, p464; Mills SY. (1993) Out of the Earth: The Essential Book of Herbal Medicine, London: Arkana, p280.

45 Gagnier JJ, Oltean H, van Tulder MW, et al. (2016) Herbal medicine for low back pain: A Cochrane review. Spine (Phila Pa 1976) 41: 116-133.

46 Jadoon S, Karim S, Hassan Bin Asad MH, et al. (2015) Anti-aging potential of phytoextract loaded-pharmaceutical creams for human skin cell longevity. Oxid Med Cell Longev 2015: ID 709628.

47 Hubert J, Angelis A, Aligiannis N, et al. (2016) In vitro dermo-cosmetic evaluation of bark extracts from common temperate trees. Planta Med 82: 1351-1358.

48 Yatkin E, Polari L, Laajala T, et al. (2014) Novel lignan and stilbenoid mixture shows anticarcinogenic efficacy in preclinical PC-3M-luc2 prostate cancer model. PLoS One 9: e93764.

49 Klein R. (2004) Phytoecdysteroids. Journal of the American Herbalists Guild Fall/Winter: 18-28.

50 Desgagné-Penix I. (2017) Distribution of alkaloids in woody plants. Plant Science Today 4: 137-142.

51 Willis (2017) p29.

52 Wang H, Zhu C, Ying Y, et al. (2018) Metformin and berberine, two versatile drugs in treatment of common metabolic diseases. Oncotarget 9: 10135–10146.

53 See Appendix 6(C) for details of herbal medicine organisations.