Horse-chestnut

Shiny, brown seed

In May the horse chestnut bears erect panicles of white flowers with flecks of yellow to red – these are nectar- (or floral) guides that direct insects to the nectar. After flowering spiky green husks appear from which a large, glossy, brown seed - the conker - falls in the autumn.

Aesculus hippocastanum originates from the Balkans, Greece and Bulgaria where it grows up to altitudes of 1500 meters. Today in the wild the species is considered to be endangered as there are no more than about 10,000 individuals. However as a result of human involvement, the horse chestnut has been planted the world over.

Two diseases however are taking their toll: bleeding canker, a bacterium that affects the phloem, and the horse chestnut leaf miner, the larvae of which can damage the leaf tissue.

Horse chestnuts with twisted branches are known as Aesculus hippocastanum 'Tortuosa’.

After beech, oak and lime the horse chestnut is listed as being the most popular tree planted as a focal point in towns and villages in the Netherlands. It is a large tree of up to 25 m tall with a domed top, a crown of consistently equal diameter from bottom to top and a trunk of about 5 m in circumference. The tree can live for about 150 years, although some exceptions are known to be as old as 300 years. In the juvenile stage there is a risk of sunburn to the thin, young bark, as a thicker outer bark is only formed when mature.

The buds are sticky. Leaves have 5-7 sessile, obovate leaflets that are irregularly toothed. On the under side of the leaf axils there are tufts of brown hair. The horse chestnut is one of the earliest flowering trees with leaf and flower buds, which form terminal ‘candles’, appearing simultaneously usually in the second half of May.

The inflorescences are up to 30 cm long and up to 10 cm in diameter. The 4-5 white petals, which bear a yellow macula (or spot), darken from pink to a red-pink. There are usually seven stamens that extend beyond the petals whilst the ovaries are covered with glandular hairs. The bases of these develop into the spines of the husk. Sometimes there are two seeds enclosed within the husk.