It is widely cultivated in streets and parks throughout the
temperate world, and has been particularly successful in places like
Ireland, Great Britain and New Zealand, where it is 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 the seeds 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. The horse-chestnut is a favorite subject for
bonsai. 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.
Aesculus hippocastanum is affected by the leaf-mining moth
Cameraria ohridella, whose larvae feed on horse chestnut leaves. The moth was described from
North Macedonia where the species was discovered in 1984 but took 18 years to reach Britain. In Germany, they are commonly planted in
beer gardens, particularly in
Bavaria. Prior to the advent of mechanical refrigeration, brewers would dig cellars for
lagering. To further protect the cellars from the summer heat, they would plant horse chestnut trees, which have spreading, dense canopies but shallow roots which would not intrude on the caverns. The practice of serving beer at these sites evolved into the modern beer garden. An inexpensive detergent for washing clothes can be made at home from conkers, and this is said to be an environmentally benign ('eco-friendly') detergent.
Traditional medicine and research The seed
extract standardized to around 20 percent
aescin (escin) is possibly useful in
traditional medicine for its effect on
venous tone. A 2012
Cochrane Review of low-quality studies suggested that horse chestnut seed extract may be an efficacious and safe short-term treatment for
chronic venous insufficiency, but definitive
randomized controlled trials had not been conducted to confirm the efficacy.
Safety There is risk of
acute kidney injury, "when patients, who had undergone cardiac surgery were given high doses of horse chestnut extract i.v. for postoperative
oedema. The phenomenon was dose dependent as no alteration in kidney function was recorded with 340 μg/kg, mild kidney function impairment developed with 360 μg/kg and acute kidney injury with 510 μg/kg". Raw horse chestnut seed, leaf, bark and flower are toxic due to the presence of
aesculin and should not be ingested. Horse chestnut seed is classified by the FDA as an unsafe herb. The
glycoside and
saponin constituents are considered toxic. ==Diseases==