Aesculus hippocastanum

Aesculus hippocastanum, the horse chestnut,[1][2][3] is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is a large deciduous, synoecious (hermaphroditic-flowered) tree.[4] It is also called horse-chestnut,[5] European horsechestnut,[6] buckeye,[7] and conker tree.[8] It is sometimes called Spanish chestnut.[7][9][10] This name is typically used for Castanea sativa.[11][12]

Aesculus hippocastanum is a large tree, growing to about 39 metres (128 ft) tall[13]:371 with a domed crown of stout branches; on old trees the outer branches are often pendulous with curled-up tips. The leaves are opposite and palmately compound, with 5–7 leaflets; each leaflet is 13–30 cm (5–12 in) long, making the whole leaf up to 60 cm (24 in) across, with a 7–20 cm (3–8 in) petiole. The leaf scars left on twigs after the leaves have fallen have a distinctive horseshoe shape, complete with seven “nails”. The flowers are usually white with a yellow to pink blotch at the base of the petals;[13] they are produced in spring in erect panicles 10–30 cm (4–12 in) tall with about 20–50 flowers on each panicle. Its pollens are not poisonous for honey bees.[14] Usually only 1–5 fruits develop on each panicle; the shell is a green, spiky capsule containing one (rarely two or three) nut-like seeds called conkers or horse-chestnuts. Each conker is 2–4 cm (3⁄4–1 1⁄2 in) in diameter, glossy nut-brown with a whitish scar at the base.[15]