Aesculus

The genus Aesculus (/ˈɛskjʊləs/[1] or /ˈaɪskjʊləs/), with varieties called buckeye and horse chestnut, comprises 13–19 species of flowering plants in the soapberry and lychee family, Sapindaceae. They are trees and shrubs native to the temperate Northern Hemisphere, with six species native to North America and seven to thirteen species native to Eurasia. Several hybrids occur. Aesculus exhibits a classical Arcto-Tertiary distribution.[lower-alpha 1]

For the Ancient Greek playwright, see Aeschylus.
"Horse chestnut" redirects here. For other uses, see Horse chestnut (disambiguation).
"Red chestnut" redirects here. For the moth with this name, see Cerastis rubricosa.

Aesculus
Aesculus hippocastanum
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Sapindaceae
Subfamily: Hippocastanoideae
Genus: Aesculus
L.
Type species
Aesculus hippocastanum
Species
Aesculus glabra Ohio buckeye
Flower of Aesculus x carnea, the red horse chestnut

Mexican buckeye seedpods resemble the Aesculus seedpods, but belong to a different genus.

Carl Linnaeus named the genus Aesculus after the Roman name for an edible acorn. Common names for these trees include "buckeye" and "horse chestnut", though they are not in the same order as chestnut trees. Some are also called white chestnut or red chestnut. In Britain, they are sometimes called conker trees because of their link with the game of conkers, played with the seeds, also called conkers.

Description

Aesculus species have stout shoots with resinous, often sticky, buds; opposite, palmately divided leaves, often very large—to 65 cm (26 in) across in the Japanese horse chestnut Ae. turbinata. Species are deciduous or evergreen. Flowers are showy, insect- or bird-pollinated, with four or five petals fused into a lobed corolla tube, arranged in a panicle inflorescence. Flowering starts after 80–110 growing degree days. The fruit matures to a capsule 2–5 cm (0.8–2.0 in) diameter, usually globose, containing one to three seeds (often erroneously called a nut) per capsule. Capsules containing more than one seed result in flatness on one side of the seeds. The point of attachment of the seed in the capsule (hilum) shows as a large circular whitish scar. The capsule epidermis has "spines" (botanically: prickles) in some species, while other capsules are warty or smooth. At maturity, the capsule splits into three sections to release the seeds.[3][4][5]

Aesculus seeds were traditionally eaten, after leaching, by the Jōmon people of Japan over about four millennia, until 300 AD.[6][7][8]

All parts of the buckeye or horse chestnut tree are moderately toxic, including the nut-like seeds.[9][10] The toxin affects the gastrointestinal system, causing gastrointestinal disturbances. The USDA notes that the toxicity is due to saponin aescin and glucoside aesculin, with alkaloids possibly contributing.[11]

Native Americans used to crush the seeds and the resulting mash was thrown into still or sluggish waterbodies to stun or kill fish.[11][12] They then boiled and drained (leached) the fish at least three times to dilute the toxin's effects.[13] New shoots from the seeds also have been known to kill grazing cattle.[14]

The genus was considered to be in the ditypic family Hippocastanaceae along with Billia,[15] but phylogenetic analysis of morphological[16] and molecular data[17] has more recently caused this family, along with the Aceraceae (maples and Dipteronia), to be included in the soapberry family (Sapindaceae).

Selected species

The species of Aesculus include:

ImageScientific nameCommon NameDistribution
Aesculus assamicaNE India (Sikkim) eastward to S China (Guangxi) and N Vietnam
Aesculus hippocastanumHorse chestnutEurope, native to the Balkans; Northeastern North America[18]
Aesculus indicaIndian horse chestnuteastern Asia
Aesculus × carnea (A. pavia x A. hippocastanum)red horse chestnutCentral Europe; cultivated elsewhere
Aesculus chinensisChinese horse chestnuteastern Asia
Aesculus chinensis var. wilsoniiWilson's horse chestnuteastern Asia
Aesculus californicaCalifornia buckeyewestern North America
Aesculus flava (A. octandra)yellow buckeyeeastern North America
Aesculus glabraOhio buckeyeeastern North America
Aesculus neglectadwarf buckeyeeastern North America
Aesculus parviflorabottlebrush buckeyeeastern North America
Aesculus parryiParry's buckeyewestern North America, endemic to Baja California del Norte
Aesculus paviared buckeyeeastern North America
Aesculus pavia var. flavescensTexas yellow buckeye, yellow woolly buckeyeeastern North America, narrowly endemic to Texas
Aesculus sylvaticapainted buckeyeeastern North America
Aesculus turbinataJapanese horse-chestnutJapan
Aesculus wangiiHorse chestnuteastern Asia

Cultivation

The most familiar member of the genus worldwide is the common horse chestnut, Aesculus hippocastanum. 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 is the bottlebrush buckeye, Aesculus parviflora, a 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 Aesculus × carnea, a hybrid between A. hippocastanum and A. pavia.

In art
Column details in the Reims Cathedral depicting horse chestnut tree leaves

Interpretations of the tree leaves can be seen in architectural details in the Reims Cathedral.

In history

The leaf of Aesculus was the official symbol of Kyiv (the 8th largest city in Europe) on its coat of arms used from 1969 to 1995.[19] It remains an official symbol of Kyiv to this day.[19]

In the 1840 U.S. presidential campaign, candidate William Henry Harrison called himself the "log cabin and hard cider candidate", portraying himself sitting in a log cabin made of buckeye logs and drinking hard cider, causing Ohio to become known as "the Buckeye State".[20]

References
  1. This designation has as a part of it a term, 'Tertiary', that is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.[2]
  1. Sunset Western Garden Book, 1995:606–607
  2. Ogg, J.G.; Gradstein, F.M.; Gradstein, F.M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 978-0-521-78142-8.
  3. Hardin, JW. 1957. A revision of the American Hippocastanaceae I. Brittonia 9:145-171
  4. Hardin, JW. 1957. A revision of the American Hippocastanaceae II. Brittonia 9:173-195
  5. Hardin, JW. 1960. A revision of the American Hippocastanaceae V, Species of the Old World. Brittonia 12:26-38
  6. Harlan, Jack R. (1995). The Living Fields: Our Agricultural Heritage (1. publ. ed.). Cambridge [u.a.]: Cambridge Univ. Press. p. 15. ISBN 978-0-521-40112-8.
  7. Akazawa, T.; Aikens, C.M. (1986). Prehistoric Hunter-Gathers in Japan. University of Tokyo Press.
  8. Aikens, C.M.; Higachi, T. (1982). Prehistory of Japan. New York Academic Press.
  9. Hall, Alan (1976). The Wild Food Trail Guide (second ed.). New York: Holt, Rhinehart and Winston. p. 214.
  10. Peterson, Lee (1977). A field guide to edible wild plants of eastern and central North America. Boston: Houghton Mifflin Co. p. 172.
  11. Nelson, Guy (2006). Ohio Buckeye (Aesculus glabra Willd.), Plant Guide. Washington, D.C.: US Department of Agriculture, Natural Resources Conservation Service.
  12. Dale, Thomas R.; Scogin, Dixie B. (1988). 100 woody plants of Louisiana. Monroe, Louisiana: The Herbarium of Northeast Louisiana University. p. 118.
  13. Fishing with Poisons
  14. Guide to Poisonous Plants
  15. Hardin, JW. 1957. A revision of the American Hippocastanaceae I. Brittonia 9:145-171.
  16. Judd, W.S.; Sanders, R.W.; Donoghue, M.J. (1994). "Angiosperm family pairs". Harvard Papers in Botany. 1: 1–51.
  17. Harrington, Mark G.; Edwards, Karen J.; Johnson, Sheila A.; Chase, Mark W.; Gadek, Paul A. (Apr–Jun 2005). "Phylogenetic inference in Sapindaceae sensu lato using plastid matK and rbcL DNA sequences". Systematic Botany. 30 (2): 366–382. doi:10.1600/0363644054223549. JSTOR 25064067. S2CID 85868684.
  18. New York Flora Atlas: Aesculus hippocastanum
  19. "'Thujoy Khreshchatyk'. Why Kyivans miss chestnuts and how they became a symbol of the capital", Ukrayinska Pravda (29 May 2019) (in Ukrainian)
  20. Carnival Campaign: How the Rollicking 1840 Campaign of "Tippecanoe and Tyler Too" Changed Presidential Elections Forever, by Ronald Shafer, 2016
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