Aesculus hippocastanum

Aesculus hippocastanum

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Aesculus hippocastanum

Aesculus hippocastanum is a large deciduous tree, commonly known as Horse-chestnut or Conker tree. It is native to a small area in the mountains of the Balkans in southeast Europe, in small areas in northern Greece, Albania, the Republic of Macedonia, Serbia, and Bulgaria (Pindus Mountains mixed forests and Balkan mixed forests).^[1] It is widely cultivated throughout the temperate world.

Growth
Etymology
Uses
References
External links

Growth

Foliage and flowers

It grows to 36 m tall, with a domed crown of stout branches, on old trees the outer branches 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 flowers are usually white with a small red spot; they are produced in spring in erect panicles 10-30 cm tall with about 20-50 flowers on each panicle. Usually only 1-5 fruit develop on each panicle; the fruit is a green, softly 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.^[2]

Etymology

The name is very often given as just 'Horse-chestnut' or 'Horse Chestnut'; the addition of 'Common' to the name helps distinguish it from other species of horse-chestnut. Despite its common name, the Horse-chestnut is not related to the Chestnuts (Castanea), which are members of the Beech faimily (Fagaceae). The Horse-chestnut is in the Buckeye family (Hippocastanaceae) and is in the same genus as other buckeyes, Aesculus. The Horse-chestnut has its common name due to the husks of the conkers being spiny and the conkers themselves shiny brown like the Chestnuts.^[3] It is also claimed that the name is derived from the horse-shoe mark left on the twig after the leaf drops in Autumn.

Uses

Leaves and trunk

Cultivation for its spectacular spring flowers is successful in a range of climatic conditions provided summers are not too hot, with trees being grown as far north as Edmonton, Alberta,^[4] the Faroe Islands,^[5] and Harstad, Norway. In more southern areas, growth is best in cooler mountain climates.

In Britain and Ireland, the nuts are used for the popular children's game conkers. During the two world wars, horse-chestnuts were used as a source of starch which in turn could be used via the Clostridium acetobutylicum fermentation method devised by Chaim Weizmann to produce acetone. This acetone was then used as a solvent which aided in the process of ballistite extrusion into cordite, which was then used in military armaments.

The nuts, 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. Some mammals, notably deer, are able to break down the toxins and eat them safely. They are reputed to be good for horses with wind, but this is unproven and feeding them to horses is not advisable. The saponin aescin, however, has been used for health purposes (such as varicose veins, edema, sprains) and is available in food supplements, as is a related glucoside aesculin.^[6]

A selection of fresh conkers from a Horse-chestnut.

In the past, Horse-chestnut seeds were used in France and Switzerland for whitening hemp, flax, silk and wool. They contain a soapy juice, fit for washing of linens and stuffs, for milling of caps and stockings, etc., and for fulling of cloth. For this, 20 horse-chestnut seeds were sufficient for six liters of water. They were peeled, then rasped or dried, and ground in a malt or other mill. The water must be soft, either rain or river water; hard well water will not work. The nuts are then steeped in cold water, which soon becomes frothy, as with soap, and then turns milky white. The liquid must be stirred well at first, and then, after standing to settle, strained or poured off clear. Linen washed in this liquid, and afterwards rinsed in clear running water, takes on an agreeable light sky-blue colour. It takes spots out of both linen and wool, and never damages or injures the cloth.

In Bavaria the chestnut is the typical tree for a beer garden. Originally they were planted for their deep shade which meant that beer cellar owners could cut ice from local rivers and lakes in winter to cool their beer well into summer. Nowadays guests enjoy the shade to keep their heads cool - even after the second Maß (a mug with a liter of beer).

"Whitening" fluorescent aesculin (aescin) from bark

Conkers have been threatened by the leaf-mining moth Cameraria ohridella, whose larvae feed on horse chestnut leaves. The moth had been in Europe since 1985 but took 17 years to reach Britain.

Aesculus hippocastanum is used in Bach flower remedies. When the buds are used it is referred to as "Chestnut Bud" and when the flowers are used it is referred to as "White Chestnut".

The flower is the symbol of the city of Kiev, capital of Ukraine.^[7]

Germination on lawn

Horse-chestnuts can be used to make jewelry using the conkers as beads.

Although the Horse-chestnut is sometimes known as the buckeye, this name is generally reserved for the New World members of the Aesculus genus.

A famous specimen is the Anne Frank Tree, a horse chestnut in the center of Amsterdam which she mentioned in her diary and which survives there to the present.