Everything about Aesculus totally explained
» For the South African Thoroughbred racehorse see: Horse Chestnut (horse).
The genus
Aesculus comprises 20–25 species of
deciduous trees and
shrubs native to the temperate
northern hemisphere, with 7–10 species native to
North America and 13–15 species native in
Eurasia; there are also several natural
hybrids. They have traditionally been treated in their own usually monogeneric family
Hippocastanaceae, but genetic evidence has led to this family, along with the
Aceraceae (
Maples and
Dipteronia), being included in the soapberry family (
Sapindaceae).
The North American species are known as
Buckeyes and the Eurasian species as
Horse-chestnuts. Some are also called "White Chestnut" or "Red Chestnut" (as in some of the
Bach flower remedies. In Britain, they're sometimes called "Conker trees" because of their link with the game of
Conkers ).
Etymology
The name Horse-chestnut, hyphenated here to avoid confusion with the true
chestnuts (
Castanea,
Fagaceae), is also often given as "Horse Chestnut" or "Horsechestnut". One species very popular in cultivation, the Common Horse-chestnut
Aesculus hippocastanum is also often known as just "Horse-chestnut". Linnaeus named the genus
Aesculus after the Roman name for an edible acorn. The use of the term "horse" refers to their strength or inedibility, the word "horse" originally meant strong or powerful, and doesn't here refer to their fitness as fodder for horses, except in folk etymology. The name buckeye derives from the resemblance of the seed to the brown eye of a buck (male
deer), and horse-chestnut from the external resemblance of the seed to a chestnut, but being inedible. The Buckeye blooms in summer and the Horse-chestnut in late spring.
Description
Aesculus are
woody plants from 4 to 36m tall (depending on species), and have stout shoots with resinous, often sticky, buds; opposite, palmately divided leaves, often very large (to 65 cm across in the Japanese Horse-chestnut
Aesculus turbinata); and showy insect-pollinated
flowers, with four or five
petals fused into a lobed
corolla tube. Flowering starts after 80–110
growing degree days. The fruit is a rich glossy brown to blackish-brown
nut 2–5 cm diameter, usually globose with one nut in a green or brown husk, but sometimes two nuts together in one husk, in which case the nuts are flat on one side; the point of attachment of the nut in the husk shows as a large circular whitish scar. The husk has spines in some species, spineless in others, and splits into three sections to release the nut.
Cultivation
The most familiar member of the genus worldwide is the
Common Horse-chestnut Aesculus hippocastanum, native to a small area of the
Balkans in southeast
Europe, but widely cultivated throughout the temperate world. The Yellow Buckeye
Aesculus flava (syn.
A. octandra) is also a valuable ornamental tree with yellow flowers, but is less widely planted. Among the smaller species, the Bottlebrush Buckeye
Aesculus parviflora also makes a very interesting and unusual flowering shrub. Several other members of the genus are used as ornamentals, and several horticultural hybrids have also been developed, most notably the Red Horse-chestnut
A. × carnea, a hybrid between
A. hippocastanum and
A. pavia.
They are generally fairly problem-free, though a recently discovered leaf-mining
moth Cameraria ohridella is currently causing major problems in much of Europe, causing premature leaf fall which looks very unattractive. The symptoms (brown blotches on the leaves) can be confused with damage caused by the leaf fungus
Guignardia aesculi, which is also very common but usually less serious. Common Horse-chestnut is also used as a food plant by the
sycamore, another species of moth.
Another disease in parts of North West Europe and North America is
Bleeding canker (External Link
).
Uses
The nuts contain high concentrations of a
saponin-class toxin called
Aesculin, which is toxic to many animals including humans because it causes
hemolysis (destruction of
red blood cells). The saponin can be eliminated by leaching the pulverized nuts in multiple changes of boiling water, to yield a wholesome
starchy
porridge once important to some
Native American tribes. Some animals, notably
deer and
squirrels, are resistant to the toxins and can eat the nuts directly. An interesting side-note is that Aesculin is a natural
pH indicator which, when extracted turns from colorless to fluorescent blue under
UV light in an acidic
pH range.
Crushed buckeye nuts have also been thrown into
lakes by
poachers, to kill fish for easy capture.
California Buckeyes
Aesculus californica are known to cause poisoning of
honeybees from toxic
nectar (other locally native
bee species not being affected). Other buckeye species are thought to have the same effect, but the toxins are diluted because the trees are not usually abundant enough in any one area.
The wood is very pale whitish-brown, fairly soft and little-used. Uses include cheap furniture, boxes and firewood.
In
Britain and
Ireland the game of
conkers remains a common childhood pastime.
In some cultures, the buckeye tree is thought to bring good luck.
(External Link
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)
The
Mexican Buckeye is related to
Aesculus, but is in a separate genus,
Ungnadia.
Extractives of the seeds have been shown to be useful for the treatment of chronic venous insufficiency.
Further Information
Get more info on 'Aesculus'.
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