The deciduous horse chestnut tree is native to the Balkans and parts of southern Europe such as Greece and Serbia. It grows well in cool or temperate climates and flourishes in the UK. Its fruit is called the horse chestnut, or conker.
Horse chestnuts grow up to 32 metres (108 feet) tall. The shape is domed, with leaves divided into five to seven lobes. White flowers grow on upright stalks (panicles), later forming one to five nuts encased in a spiny case.
Horse chestnuts are not chestnuts but are part of the buckeye family. Their fruit is not edible.
Conkers is a traditional game in the UK and Ireland. Children pierce a horse chestnut, thread a knotted string through and use it to strike the opponent's conker. The winner is the one who "conquers" the other conkers.
Horse chestnut seeds were used to wash natural fibres such as wool. A substance in the bark, aescin, has been used in medicine for sprains and varicose veins, and also in Bach flower remedies. Horse chestnuts are also planted as shade trees.
In 2008, the Top Gear TV programme staged a game of conkers using cranes and mobile homes. The World Conker Championships have been held since 1965.