Chestnut, horse (Aesculus hippocastanum)

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Horse chestnut is a deciduous broadleaf tree native to the Balkan peninsula.

Common name: horse chestnut

Scientific name: Aesculus hippocastanum
Family: Hippocastanaceae

UK provenance: non-native

Interesting fact: the leaf stalks leave a scar on the twig when they fall, which resembles an inverted horse shoe with nail holes. This association with horses could explain why conkers used to be ground up and fed to horses to relieve them of coughs, and could be the origin of the tree's name.

What does horse chestnut look like?

Overview: mature horse chestnut trees grow to a height of around 40m, and can live for up to 300 years. The bark is smooth and pinky grey when young, which darkens and develops scaly plates with age. Twigs are hairless and stout, buds are oval, dark red, shiny and sticky.

Leaves: the palmate leaves comprise 5-7 pointed, toothed leaflets spreading from a central stem.

Flowers: appearing in May - individual flowers have 4-5 fringed petals, which are white with a pink flush at the base. 

Fruits: once pollinated by insects, each flower develops into a glossy red-brown conker inside a spiky green husk, which falls in autumn. 

Look out for: conkers (seeds) are surrounded by a spiky green case. Distinctive large leaves have serrated leaflets.

Could be confused with: unlikely to be confused with anything.

Identified in winter by: twigs have large sticky red buds.

Where to find horse chestnut

 It is rarely found in woodland, but is a common site in parks, gardens, streets and village greens. Horse chestnut was first introduced from Turkey in the late 16th century and widely planted in the UK.

Value to wildlife

The flowers provide a rich source of nectar and pollen to insects, particularly bees. Caterpillars of the triangle moth feed on its leaves, as well as the horse chestnut leaf miner moth, whose caterpillars provide food for blue tits. Deer and other mammals eat the conkers.

Mythology and symbolism

There is little folklore associated with the tree - probably due to it being an introduced species. However, games of conkers have different rules in different parts of the country, which have their own jargon and often require the repeating of rhymes or rituals to decide who goes first.

How we use horse chestnut

The most famous use of horse chestnut is in the game of conkers. The first record of the game is from the Isle of Wight in 1848. 

Horse chestnut timber is a pale creamy white to light brown with a smooth, soft, fine texture. It's not very strong and is therefore not used commercially, but its soft texture makes it ideal for carving.

Other uses of the conkers include horse medicines, as additives in shampoos and as a starch substitute. Chemicals extracted from conkers can be used to treat strains and bruises.

Threats

Horse chestnut has been found to be susceptible to fungal diseases. Trees can also be affected by bleeding canker, which can lead to their death.

The horse chestnut leaf miner can occur on trees in huge numbers, causing the foliage to turn brown and fall early. There is no evidence to suggest this harms the trees, as most of the damage occurs late in the season.

Horse chestnuts may also suffer from Guignardia leaf blotch and horse chestnut scale insect. 

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