Horse chestnut  (Aesculus hippocastanum)

A common introduced species in the UK.

The ‘spreading chestnut tree’, a common sight on village greens and alongside housing developments, is not actually native to Britain. It arrived in the sixteenth century and was grown, initially, as a specimen tree in collections such as that of the plant collector John Tradescant. Only later did it begin the process of naturalisation, probably as a result of extensive planting by landscape designers like ‘Capability’ Brown and Sir Christopher Wren, who planted a mile-long avenue of them at Bushy Park near Hampton Court.

Horse chestnut is one of the easiest British trees to identify and its leaves are often the earliest to appear. They are preceded by the famous ‘sticky buds’, and soon open to form the familiar five to seven-fingered leaflets on a stiff green stem. The tree produces an abundant show of upright white flower spikes that are arranged round the canopy like candles. The bark is well fissured, especially on older trees where it fractures into plates whose ends gradually curl away from the trunk. The most familiar product of the tree is its conkers, contained in a spiky green husk and often produced in abundance. These have become the centre-piece of one of the most enduring childhood games. There may be two or three conkers, with flat sides arranged together, or one large single conker in the husk.

Horse chestnuts are a native of Greece and the Balkans, but have been introduced to many temperate countries around the world. In the UK, it occurs virtually everywhere except the Scottish Grampian regions and the extreme northwest mainland and islands.

You can view distribution information for this species at the National Biodiversity Network Gateway.

As an introduced species, horse chestnut can be found in parks, large gardens and estates, but it also occurs in the wild as a naturalised tree on various habitat types, ranging from damp fens and woods to upland road verges.

Horse chestnut is in leaf from early April and the flowers follow soon after. As many a schoolchild will know, the conkers appear in September and fall as they ripen, although many are helped on their way by a well-aimed stick. They are often eaten by deer and wood pasture-grazed cattle. When left uneaten, conkers will strike quickly and rapidly grow into good-sized saplings. If this happens near a building, it is advisable to remove the tree as soon as possible as a mature horse chestnut will be expensive to remove. The branches are brittle and may be shed without notice, and its roots will damage foundations and cause subsidence.

The timber from horse chestnut is light in weight and not very strong and, other than pulp wood, has very few uses commercially although it was once used to make artificial limbs. This may be one reason why so many older trees survive to become large, so large in some cases, that they can exceed two metres in diameter.

The horse chestnut is not threatened in the UK.

There are currently no conservation projects for the horse chestnut.

There may be further information about this species available via the National Biodiversity Network Gateway.