Aesculus hippocastanum

Aesculus hippocastanum is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is a large deciduous, synoecious (hermaphroditic-flowered) tree, commonly known as horse-chestnut or conker tree. Aesculus hippocastanum is a large tree, growing to about 39 metres (128 ft) tall: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 long, making the whole leaf up to 60 cm across, with a 7–20 cm 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; they are produced in spring in erect panicles 10–30 cm tall with about 20–50 flowers on each panicle. Its pollens are not poisonous for honey bees. 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 diameter, glossy nut-brown with a whitish scar at the base. The common name 'horse-chestnut' (often unhyphenated) is reported as having originated from the erroneous belief that the tree was a kind of chestnut (though in fact only distantly related), together with the observation that the fruit could help panting horses. Aesculus hippocastanum is native to a small area in the Pindus Mountains mixed forests and Balkan mixed forests of South East Europe. However, it can be found in many parts of Europe as far north as Gästrikland in Sweden, as well as in many parks and cities in the United States and Canada. It is widely cultivated in streets and parks throughout the temperate world, and has been particularly successful in places like Ireland, the United Kingdom and New Zealand, where they are commonly found in parks, streets and avenues. Cultivation for its spectacular spring flowers is successful in a wide range of temperate climatic conditions provided summers are not too hot, with trees being grown as far north as Edmonton, Alberta, Canada, the Faroe Islands, Reykjavík, Iceland and Harstad, Norway. In Britain and Ireland, the seeds are used for the popular children's game conkers. During the First World War, there was a campaign to ask for everyone (including children) to collect horse-chestnuts and donate them to the government. The conkers were used as a source of starch for fermentation using the Clostridium acetobutylicum method devised by Chaim Weizmann to produce acetone for use as a solvent for the production of cordite, which was then used in military armaments. Weizmann's process could use any source of starch, but the government chose to ask for conkers to avoid causing starvation by depleting food sources. But conkers were found to be a poor source, and the factory only produced acetone for three months; however, they were collected again in the Second World War for the same reason. The seeds, especially those that are young and fresh, are slightly poisonous, containing alkaloid saponins and glucosides. Although not dangerous to touch, they cause sickness when eaten; consumed by horses, they can cause tremors and lack of coordination. Though the seeds are said to repel spiders there is little evidence to support these claims. The presence of saponin may repel insects but it is not clear whether this is effective on spiders.