Aesculus hippocastanum

Aesculus hippocastanum, the horse chestnut,Template:R is a species of flowering plant in the maple, soapberry and lychee family Sapindaceae. It is a large, deciduous, synoecious (hermaphroditic-flowered) tree.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is also called horse-chestnut,<ref name=BSBI07>Template:BSBI 2007</ref> European horsechestnut,Template:R buckeye,Template:R and conker tree.Template:R It is not to be confused with the sweet chestnut or Spanish chestnut, Castanea sativa, which is a tree in another family, Fagaceae.<ref name=Stace>Template:Cite book</ref>Template:Rp

Description

Aesculus hippocastanum is a large tree, growing to about Template:Convert tall<ref name=Stace/> 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 Template:Convert long, making the whole leaf up to Template:Convert across, with a Template:Convert 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;<ref name=Stace/> they are produced in spring in erect panicles Template:Convert tall with about 20–50 flowers on each panicle. Its pollen is not poisonous for honey bees.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 Template:Convert in diameter, glossy nut-brown with a whitish scar at the base.<ref name=rushforth>Template:Cite book</ref>

File:Horse chestnut flowers in Brodalen 4.jpg

Inflorescence

File:Aesculus hippocastanum floral diagram colored.svg

Floral diagram of A. hippocastanum. The light green structure denotes nectary. Floral formula: ↘ K5 C2:2 A5+2 G(3).

Etymology

The common name horse chestnut originates from the similarity of the leaves and fruits to sweet chestnuts, Castanea sativa (a tree in a different family, the Fagaceae),<ref name=Stace/> together with the alleged observation that the fruit or seeds could help panting or coughing horses.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref>

Although it is sometimes known as buckeye,Template:R for the resemblance of the seed to a deer's eye, the term buckeye is more commonly used for New World members of the genus Aesculus.Template:R

Distribution and habitat

The native distribution of Aesculus hippocastanum given by different sources varies. Template:As of, Plants of the World Online considered it to be native to the Balkans (Albania, Bulgaria, Greece and former Yugoslavia), but also to Turkey and Turkmenistan.<ref name="POWO_781594-1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A 2017 assessment for the IUCN Red List restricted the native distribution to the Balkan area: Albania, Bulgaria, mainland Greece and North Macedonia.<ref name=IUCN/> It has been introduced and planted around the world. It can be found in many parts of Europe as far north as Harstad north of the Arctic Circle in Norway,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and Gästrikland in Sweden as well as in many parks and cities around the northern US and Canada such as Edmonton in Alberta, Canada.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The compact native population of horse chestnut in Bulgaria is distinct from the horse chestnut forests of northern Greece, western North Macedonia and Albania. It is limited to an area of Template:Cvt in the Preslav Mountain north of the Balkan Mountains, in the valleys of the Dervishka and Lazarska rivers. Bulgaria's relict horse chestnut forests are critically endangered at the national level and protected as part of the Dervisha Managed Nature Reserve.<ref name="bas">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Uses

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,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the Faroe Islands,<ref>Template:Cite journal</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

File:Aesculus hippocastanum fruit.jpg

A selection of fresh conkers

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.<ref>Template:Cite book</ref>

The horse-chestnut is a favorite subject for bonsai.<ref name="Ma-Ke_Aesculus hippocastanum">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref name='RSC'>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref name="Lees et al. 2009">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>Template:Cite news</ref>

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Traditional medicine and research

File:Beta-Aescin.svg

Aescin

The seed extract standardized to around 20 percent aescin (escin) is possibly useful in traditional medicine for its effect on venous tone.<ref>Template:Cite journal</ref><ref name= nccih>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>Template:Cite journal</ref>

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".<ref>Template:Cite book</ref>

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.<ref name=mskcc>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The glycoside and saponin constituents are considered toxic.<ref name=mskcc/>

Anne Frank tree

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} A horse-chestnut tree stood outside the window of the "secret annex" in the centre of Amsterdam, which Anne Frank mentioned in her diary; the tree survived until August 2010, when a heavy wind blew it over.<ref>Template:Cite news</ref><ref>Template:Cite news</ref> Eleven young specimens, sprouted from seeds from this tree, were transported to the United States. After a long quarantine in Indianapolis, each tree was shipped off to a new home at a notable museum or institution in the US, such as 9/11 Memorial Park, Little Rock Central High School, and two Holocaust Centers. One of them was planted outdoors in March 2013 in front of The Children's Museum of Indianapolis, where they were originally quarantined.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Symbol of Kyiv

The horse chestnut tree is one of the symbols of Kyiv, the capital of Ukraine.<ref name="7253616chestnutKyivC">Template:Cite news</ref>

Diseases

File:10 Pest damage - horse-chestnut leaf miner (Cameraria ohridella) in Parma, Italy.jpg

Horse-chestnut leaf miner (Cameraria ohridella) tree damage in Parma, Italy

• Bleeding canker. Half of all horse-chestnuts in Great Britain are now showing symptoms to some degree of this potentially lethal bacterial infection.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref><ref name="suffolkcoastal">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• Guignardia leaf blotch, caused by the fungus Guignardia aesculi
• Wood rotting fungi such as Armillaria and Ganoderma
• Horse chestnut scale, caused by the insect Pulvinaria regalis
• Horse-chestnut leaf miner, Cameraria ohridella, a leaf mining moth.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> The larvae of this moth species bore through the leaves of the horse chestnut, causing premature colour changes and leaf loss.<ref name= "suffolkcoastal" />

• Phytophthora bleeding canker, a fungal infection<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }} </ref>

See also

Aesculus glabra

Other sources

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