Archive, Herbal medicine, Monographs, Plant identification help

Foraging horse chestnut

Discover the powerful medicinal benefits of horse chestnut

Aesculus hippocastanum   –  Horse Chestnut

Hippocastanaceae family

The horse-chestnut is an elegant tree which belongs to a genus of 13 species, all of them deciduous trees and shrubs. This plant is believed native to the Balkan Peninsula, and history tells us that it was introduced to Northern Europe during the latter part of the renaissance. It has been widely grown in Britain since the beginning of the 17th century.

Partly through an ability to self seed (although not freely), and mostly due to its popularity as an amenity plant, the horse-chestnut will be easily found throughout England, Wales and the more lowland parts of Scotland, at elevations of up to 500 metres. It is a common plant of parkland, large gardens, village greens, churchyards, and urban streets, and an occasional component of deciduous and mixed woodland. It can also sometimes be found in scrub and rough grasslands.

How to identify Horse chestnut

Most people will easily recognise this tree and it hardly needs a description here. The hairless new twigs terminate with large sticky buds, which are one of the characteristic identification features of this tree. Another is the noticeably large horse-shoe shaped leaf-scar on the previous year’s stem. According to some authors, this feature has given us both the scientific and common names.

horse chestnut just after breaking bud in spring

The large, noticeably glossy, and sticky brown leaf buds, break open in early spring to reveal their initially lime-green, compound palmate leaves. These are attached to the stem on long petioles. The leaves are often very large (up to 40 cm across in the common horse-chestnut found here), especially so in shadier areas. They commonly consist of 5-7 obovate-shaped leaflets, and have quite obvious serrated margins.

Horse chestnuts are identifiable from afar in winter due to their branches, which tend to curve out and upwards in a similar fashion to the unrelated and well known ash tree (Oleraceae family). In leaf, horse-chestnuts are almost unmistakeable.

Mature specimens, more often than not, show angled and curving fissures appearing to be wrapping their way around the tree in a spiral. These fissures become deep as the plant grows old, eventually splitting and flaking on very old specimens. These tall trees can grow to anything between 25-35 metres (depending on species) in a range of settings.

This plant is often the first large tree we witness to herald the coming of the new spring. Bud break is followed by the opening of their showy, white-pink coloured flowers that bloom soon afterwards.

The flowers are stacked 20-30 cm high in a cone-shaped spike. The individual flowers are 2 cm wide and borne on long stalks at the bottom of the raceme, appearing on shorter stalks toward the top. They are comprised of four or five petals fused at the base.

The resultant fruits are known to all in Britain as ‘conkers’, and to Americans as ‘buckeye nuts’. They are typically 6 cm wide. In Britain and Ireland, ‘conkers’ remains a traditional game still enjoyed by children (and adults!) These nuts are so well known in this country, coming in pairs in their typically spiny shell, that they surely need no other description here.

Be careful not to confuse the horse-chestnut with the edible sweet chestnuts (Fagaceae family) when out foraging. The sweet chestnuts have simple, oblong/elliptical-shaped leaves rather than compound, and their leaf margins are more finely serrated. Their distinctive nut husks are covered with a greater number of slightly thinner, yet sharper spines.

Sweet chestnut bark is grey-brown and more tightly fissured. Look around the woodland floor wherever you are and the leaves may well match the trees around you. In reality, the differences are so stark as to ensure that there should be no real danger of misidentifying them.

Pests and diseases attacking horse chestnut

Recently, the horse-chestnut has begun to succumb to the ravages of a few pathogenic organisms. Two species of mould fungi from the Phytophthora genus (Phyton is from the Greek for plant and phthora is Greek for destruction) are known worldwide for their mass killing of horse-chestnuts through infection and resultant ‘bleeding canker’ during the 1940’s.

These mould fungi are mostly pathogens of dicotyledons and reportedly responsible for approximately 11% of all bleeding canker incidences in Britain. Since 2003, a different species of bacterium, known as Psuedomonas syringae, has swept through horse-chestnut trees in Western Europe with a new spate of bleeding canker.

Over half of all horse-chestnut trees in Britain are reported affected and showing symptoms of some kind. This pathogen initially infects the cambium around the trunk and main branches. As it spreads, it cuts off the water supply to the crown. Trees weep from the bark, with gradual erosion of tissues. When the infection encircles the trunk, the plant will die.

The other major pest is a moth known as the horse-chestnut leaf miner (Cameraria ohridella). Many horse-chestnut specimens now show the tell-tale spotted and brown crinkled leaves which become visible early in the summer. These infections may well be the result of an exotic plant suffering the eventual fate of all exotic introductions, i.e. a population being brought under control by organisms to which there are either no natural predators or to which the plant has no natural defence mechanisms? Enjoy them while you can.

Parts used The fruits and less commonly the bark or leaves.

Harvest When they fall. Usually by mid / late September to early October.

Key constituents Saponins (including ‘aesin’ – a mixture of compounds); triterpenoid glycosides; coumarin glycosides (including aesculin); tannins; flavonoids; plant sterols (including sitosterol, stigmasterol and campesterol).

Actions Astringent, anti-inflammatory, anti-oedema.

Pharmacology and uses Anti-inflammatory activity has been documented for the whole fruit as well as the extracted saponin fraction. Extracts excluding aescin also provide this action. The anti-inflammatory effect is thought to be due to a ‘sealing’ action on capillaries as well as by reducing the number and or diameter of capillary pores. The seed extract is also known to induce contractions in veins.

Because of these effects, horse chestnut seed extract has been clinically compared to allopathic medicines for chronic venous insufficiency of the lower legs. It has shown to be just as effective as many of the pharmaceutical medications available.

Preparations made from the horse-chestnut seed are used principally against circulatory disorders. It is documented to help tone and increase the strength of the veins especially. The renowned German Commission E approved its use for treatment of chronic venous insufficiency in the legs.

Used internally and externally, horse-chestnut assists the body with inflammatory, circulatory problems such as varicose veins and haemorrhoids. This has been partly ascribed to the inhibition of the action of hyaluronidase in the body (an enzyme that decreases the permeability of the veins), and as a result, venous fragility is lowered.

Externally it may be used as a cream or ointment for the same conditions as well as for leg ulcers and oedema (fluid retention and swelling under the skin). Some studies have shown it to be effective in treating eczema. Sunscreen creams manufactured in Europe often have aesculin as an integral component.

Consulting with a professional health care worker before any self administered dosage of horse-chestnut is advisable, as the circulation disorders and physical trauma associated with any swelling may be the sign of an underlying serious condition, which may not be treatable using the plant alone.

Another monograph for foragers next week… Happy foraging!

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: