How do you sustainably harvest trees in the medicinal forest garden? What if you need to stop medicinal trees from getting too large? What works well in a permaculture design for producing botanical supplies such as bark, flowers, fruit and leaves from trees? In Part 1 of this blog I focus on pollarding as a useful approach, and in Part 2 I will consider more detail including examples of medicinal trees to pollard.
Abundance of pollarding
Pollarding of trees can be used to provide abundant quantities of leaves, flowers and fruits as a sustainable harvest which can be repeated year after year. In the past, pollarding was a well-established practice for many reasons. In traditional tree management, pollarding provided supplies for fuel, fencing, basketry, charcoal and more. It also offered a way to obtain foliage for feeding animals and, nowadays, tree fodder is coming back into fashion. However, the availability of information on using pollarding for medicinal purposes is negligible, so this two-part blog is a summary of the relevant experience that we have gained so far in pollarding trees for medicinal harvests.
Medicinal bark from pollards
Our experience has been of use of pollarding to enable a sustainable harvest from selected medicinal tree species. Usually it involves cutting the main trunk or stem at a height, from 1-2 m. This has provided an ideal way to produce medicinal bark. Long straight stems from 2 or 3 years subsequent regrowth work well for peeling bark for medicinal purposes. Some examples suggest what can be achieved with medicinal bark. Ash (Fraxinus ornata) bark is anti-inflammatory and useful in preparations for complaints such as arthritis. Cherry (Prunus avium and other cherry species) bark constituents help to suppress the cough reflex and so it is used in syrup for dry cough (not suitable for a productive cough when you do not want to suppress the coughing up of phlegm). Cramp bark (Viburnum opulus) is strongly antispasmodic and useful in symptomatic relief of painful complaints such as period pains. Alder buckthorn (Frangula alnus) bark, aged for at least a year, provides a strong laxative due to anthraquinone content. All of these barks can be harvested and dried for powdering or used to make tinctures. You can see more about the harvesting and making of preparations in The Medicinal Forest Garden Handbook (2020).
Is pollarding a good idea?
Perhaps surprisingly, pollarding does not cause damage to trees if done well and regularly. The repeated cutting back of the tree encourages fresh growth. Indeed, the overall effect of reducing height helps to lessen any tendency to suffer wind damage. It is generally thought that pollarding can improve tree health and prolong life, and there are some very ancient pollards venerated as champion trees. Traditionally the effect of keeping foliage high off the ground ensured that it was out of reach of grazing animals, and the foliage could then be cut for drying for later use as feed. For medicinal use the copious production of leaf matter is ideal for drying for herb teas or making fresh herb tinctures, useful if harvesting medicinal leaves of ginkgo, sweet chestnut, willow and others. In fruit production, if pollarded reasonably low then fruit is in range for picking from branches by hand, or perhaps within reach of short ladders. This is often seen in orchards. For medicinal supplies, the pollarding approach can be used for sourcing elderberries, hawthorn berries and other berries used in herbal medicine, providing the pollard cycle allows fruiting wood to be produced. Some other advantages of pollarding include production of desired types of wood, particularly smaller branches for fuel or making baskets. As noted above, the younger stems are great for medicinal bark supplies. There are more good reasons for pollarding, such as ornamental effect, from a rounded tree shape to regular patterns in an avenue of trees. Pollarding can be used to manage trees that would otherwise grow too large for their position, so that the extent of growth and shade is reduced. From a design perspective, pollarding provides a management technique to make medicinal tree growing viable on smaller growing sites and in forest gardens.
How do you pollard a tree?
Cut across the tree stem with a sharp tree saw (or use a chainsaw if you are properly trained and protected). Cutting creates a wound so it is important to cut cleanly across or at a slight angle so that water sheds away. Pollarding is effectively done in winter or early spring months when there is less sap to ooze, and the tree can recover more readily. In summer there is potential for warmth to increase fungal and bacterial damage from cutting although this period is supposed to be better for walnut (Juglans) and cherry (Prunus) species. The time to avoid pollarding is in autumn when fungal spores may readily enter cuts.
How often is pollarding done?
Pollarding can be carried out annually or less often. The frequency of pollarding depends on how much growth you are seeking. For young stems to produce foliage or bark, a cycle of 1 or 2 years might be appropriate. However, if you want flowers and fruits that are produced on one-year-old growth then pollard every 2 or 3 years. Longer cycles are possible too. It is important to think in the longer term to plan for a tree to be pollarded on a consistent basis.
Our experience has shown that pollarding can provide plenty to harvest for herbal medicine use! For self-sufficiency just one or two trees of each species may provide enough supplies. Strong growers like cherry and willow can be pollarded every 1-2 years when the stems are taken for bark. The ideal time to do this is just as leaves are beginning to emerge because the bark will readily peel off due to the rising sap. Other trees may be harvested for leaves every 2-3 years such as ginkgo or mulberry, and they may be pruned later in the year when the leaf crop is suitably grown. For supplies of flowers and fruit (such as hawthorn species), it is best to pollard alternate trees in winter so that there are one-year old stems to produce flower buds on some trees.
Which trees can be pollarded?
Nowadays a few species of trees are pollarded on a regular basis for ornamental purposes. Street trees such as lime and sycamore are pollarded at a high level to manage their size and appearance. It is also possible to see pollards in certain localities such as willow, pollarded at a low level, on the Somerset wetlands. When considering pollarding, it turns out that many more species of trees can be pollarded. Suitable broadleaf species include alder, ash, beech, cherry, elder, elm, eucalyptus, lime, maple, mulberry, oak, sycamore, willow and most fruit trees. Some of these species, such as elder and willow can also be coppiced by cutting close to the ground. These trees can be grown and pollarded individually or may be grown in hedging with other trees and shrubs.
See Part 2 of this blog for more on how pollarding works and individual tree species.