Plant 177

Aesculus hippocastanum L. (Sapindaceae)


Horse chestnut

Aesculus hippocastanum was introduced to Europe from the Balkan Peninsula in seventeenth century; first in France (1615), then in London (1633). Horse chestnut was recorded from the Oxford Physic Garden in 1648, although it had apparently died out by 1658. It was more than 200 years before the native distribution of the horse chestnut was discovered. The earliest reports of the species in the wild came from the Cornish mine owner and Hellenophile John Hawkins travelling in the Pindos Mountains, Greece in the late-eighteenth century.

The horse chestnut is a rapid-growing, deciduous tree that can reach 35 metres tall, with some specimens living up to 300 years. They are distinct from other trees by their large, palmate leaves. Its value lies in its ornamental qualities. Its soft, pale wood is of little value as timber or biomass, but it is ideal for carving.

Flowers appear in upright, candelabra-like, white panicles in May, and are a rich source of nectar and pollen for insects, especially bees. Horse chestnuts are important elements of the food chain in many urban environments. Leaf-feeding insects, such as the caterpillars of the chestnut leaf miner moth are food for blue tits and other small birds.

Aesculus hippocastanum produces spiky, green fruits, which ripen in September to reveal shiny, brown seeds, or 'conkers', just in time for the new school year. A favourite playground game, conkers has been played across the country for decades; the first recorded game was in 1848 on the Isle of Wight. There is even a World Conker Championship, which has taken place in Northamptonshire since 1965.

This plant's common name may come from its use as a horse medicine, which may explain its rate of spread in the UK. Blacksmiths used a mixture of horse chestnut bark and seed to treat horses with stomach complaints. Ground seeds were also used to treat horse's coughs. When its leaves drop in autumn the scar left behind even looks like a horseshoe!

Roasted conkers have been used as a coffee substitute; roasting apparently destroys toxic, bitter-tasting saponins. The horse chestnut saponins have been used as a soap alternative; grated conkers are mixed with water and 'Viking soap' is produced by straining the water off and pressing the pulp into a mould. Tea made from the bark has been used as an antimalarial medicine, whilst the saponins in conkers are believed to repel spiders and moths.

Further reading

Hemery G and Simblet S 2014. The new Sylva, a discourse of forest and orchard trees for the twenty-first century. Bloomsbury.

Johnson O and More D 2006. Tree guide. Collins.

Lack HW 2000. Lilac and horse-chestnut: discovery and rediscovery. Curtis's Botanical Magazine 17: 109-141.

Vanessa Newman