Aesculus

{{Short description|Genus of flowering plants}} {{Distinguish|text = the Ancient Greek playwright Aeschylus}} {{Redirect|Horse chestnut}} {{Redirect |Red chestnut |the moth with this name |Cerastis rubricosa{{!}}''Cerastis rubricosa''}} {{Automatic taxobox |image = Aesculus hippocastanum.001 - Culleredo.jpg |image_caption = ''Aesculus hippocastanum'', the European horse-chestnut |taxon = Aesculus |type_species = ''Aesculus hippocastanum'' |type_species_authority = L. |authority = L. |subdivision_ranks = Species |subdivision = {{hidden begin}} * ''Aesculus assamica'' (syn. ''A. wangii'') * ''Aesculus californica'' * ''Aesculus chinensis'' * ''Aesculus flava'' (syn. ''A. octandra'') * ''Aesculus glabra'' * ''Aesculus hippocastanum'' * ''Aesculus indica'' * ''Aesculus parryi'' * ''Aesculus parviflora'' * ''Aesculus pavia'' * ''Aesculus sylvatica'' * ''Aesculus turbinata'' * ''Aesculus'' × ''bushii'' * ''Aesculus'' × ''carnea'' * ''Aesculus'' × ''hybrida'' * ''Aesculus'' × ''marylandica'' * ''Aesculus'' × ''mutabilis'' * ''Aesculus'' × ''neglecta'' * ''Aesculus'' × ''woerlitzensis'' {{hidden end}} |}} [[File:Aesculus glabra USDA.jpg|thumb|''Aesculus glabra'' Ohio buckeye ]] [[File:Aesculus carnea BotGartenMuenster PurpurKastanie 6685.jpg|thumb|Flower of ''Aesculus'' × ''carnea'', the red horse-chestnut]] thumb|Germinating seed of a horse-chestnut still half-enclosed in its shell, while the root has already reached the soil

The genus '''''Aesculus''''' ({{IPAc-en|ˈ|aɪ|s|k|j|ʊ|l|ə|s}}) is a genus of flowering plants in the family Sapindaceae. They are trees and shrubs, mostly native to the temperate Northern Hemisphere, but one species (''A.&nbsp;assamica'') into subtropical areas of southeast Asia. The Plants of the World Online (POWO) database currently accepts 12 species, with seven species native to North America, four native to Asia, and one native to Europe;<ref name="POWO">{{cite web | title=''Aesculus'' L. | website=Plants of the World Online | date=2022-04-27 | url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:36263-1 | access-date=2025-12-16}}</ref> some other authors have accepted more species. Hardin (1957–1960) accepted 13 species,<ref name = hardin1957a /><ref name = hardin1957b /><ref name = hardin1960 /> the ''Trees and Shrubs Online'' website cites "13–15" species with descriptions given for 14 species,<ref name="TSO">{{cite web | title=''Aesculus'' L. | website=Trees and Shrubs Online | date=2025-12-15 | url=https://www.treesandshrubsonline.org/articles/aesculus/ | access-date=2025-12-16}}</ref> and Harris et al. (2009) accepted 16 species.<ref name="Harris">{{cite journal | last1=Harris | first1=Aj | last2=Xiang | first2=Qiu-Yun(jenny) | last3=Thomas | first3=David T. | title=Phylogeny, origin, and biogeographic history of ''Aesculus'' L. (Sapindales) – an update from combined analysis of DNA sequences, morphology, and fossils | journal=Taxon | volume=58 | issue=1 | date=2009 | issn=0040-0262 | doi=10.1002/tax.581012 | pages=108–126 | url=https://onlinelibrary.wiley.com/doi/10.1002/tax.581012 | access-date=2025-12-16| url-access=subscription }}</ref> Six natural hybrids occur,<ref name="POWO"/> and several others have been raised in cultivation. The European and Asian species are known as '''horse-chestnut''' or '''horse chestnut''', and the North American species as '''buckeye'''. ''Aesculus'' exhibits a classical Arcto-Tertiary distribution.{{efn|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.<ref>{{cite book |last1=Ogg |first1=J.G. |last2=Gradstein |first2=F.M. |last3=Gradstein |first3=F.M. |title=A geologic time scale 2004 |publisher=Cambridge University Press |location=Cambridge, UK |year=2004 |isbn=978-0-521-78142-8}}</ref>}} thumb|250px| Half-open leaf bud of a horse chestnut Aesculus hippocastanum.

Carl Linnaeus named the genus ''Aesculus'' after the Roman name for an edible acorn. The genus was considered to be in the ditypic family Hippocastanaceae along with ''Billia'',<ref name = hardin1957c /> but phylogenetic analyses of morphological<ref name=Judd /> and molecular data<ref name=phylogenetic /> have more recently caused this family, along with the Aceraceae (maples and ''Dipteronia''), to be included in the soapberry family (Sapindaceae). The fruit of the Mexican buckeye resemble ''Aesculus'' fruit, but belong to a related though different genus ''Ungnadia''.

The common name "horse chestnut" invites confusion with the chestnuts in the genus ''Castanea'' in the order Fagales; the name is often hyphenated as horse-chestnut to minimise this confusion.

==Description== ''Aesculus'' species are shrubs or trees growing to {{cvt|4|–|35|m|ft|0}} tall. They have stout shoots with resinous, often sticky, buds, with opposite, palmately divided, deciduous, leaves; these are often very large, to {{convert|65|cm|abbr=on}} across in the Japanese horse-chestnut ''A.&nbsp;turbinata''. The flowers are showy, insect- or bird-pollinated, with four or five petals fused into a lobed corolla tube, arranged in a panicle inflorescence. Flowering is in spring or summer, from February (rarely January) in ''A.&nbsp;assamica'' to July (rarely August) in ''A.&nbsp;indica'' and ''A.&nbsp;parviflora''; some species may have a small second flowering in autumn. The fruit matures to a capsule {{convert|2|-|5|cm|abbr=on|0}} 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 in others the capsules are warty or smooth. At maturity, the capsule splits into three sections to release the seeds.<ref name = hardin1957a /><ref name = hardin1957b /><ref name = hardin1960 />

==Species== The species of ''Aesculus'' accepted by POWO are:<ref name="POWO"/> {| class="wikitable" |- ! Image !! Scientific name !! Common name !! Distribution !! Notes |- |120px || ''Aesculus assamica'' || Assam horse-chestnut || Southeastern Asia from northeast India (Sikkim) eastward to southern China (Guangxi) and northern Vietnam ||Syn. ''A. wangii'' |- |120px || ''Aesculus californica''|| California buckeye ||Western North America in California || |- |120px || ''Aesculus chinensis''|| Chinese horse-chestnut ||Eastern Asia ||Two varieties often distinguished, var. ''chinensis'' and var. ''wilsonii'' |- |120px || ''Aesculus flava'' || yellow buckeye ||Eastern North America ||Syn. ''A. octandra'' |- |120px || ''Aesculus glabra''|| Ohio buckeye ||eastern North America ||Two varieties, var. ''arguta'' and var. ''glabra'' |- |120px || ''Aesculus hippocastanum''|| [common] horse-chestnut ||Southeastern Europe, in Albania, northwestern Greece, and northern Bulgaria |- |120px || ''Aesculus indica''|| Indian horse-chestnut ||Southern Asia, in the western Himalaya in northeastern Afghanistan, northern Pakistan, northwestern India and western Nepal || |- |120px || ''Aesculus parryi''|| Parry's buckeye ||Western North America, endemic to Mexico in Baja California del Norte || |- |120px || ''Aesculus parviflora''|| bottlebrush buckeye ||Southeastern North America || |- |120px || ''Aesculus pavia''|| red buckeye ||Southeastern North America ||Two varieties, var. ''flavescens'' and var. ''pavia'' |- |120px || ''Aesculus sylvatica''|| painted buckeye ||Southeastern North America || |- |120px || ''Aesculus turbinata''|| Japanese horse-chestnut ||Japan || |- |}

==Uses== ''Aesculus'' seeds were traditionally eaten, after leaching, by the Jōmon people of Japan over about four millennia, until 300&nbsp;AD.<ref name=Harlan /><ref name=Akazawa /><ref name=Aikens />

All parts of the trees are moderately toxic, but the attractive nut-like seeds are the most likely part to cause poisoning.<ref name=Hall /><ref name=Peterson /> The toxin affects the gastrointestinal system, causing gastrointestinal disturbances. The USDA notes that the toxicity is due to the saponin aescin and the glucoside aesculin, with alkaloids possibly contributing.<ref name=Nelson />

In North America, several native American tribes, particularly in the western and central United States, such as Miwok, Pomo, Yokut, Maidu, historically used buckeye seeds like California buckeye to harvest fish by using the saponins, which had been extracted by the plant's seeds. These tribes would crush buckeye seeds to release saponins into streams or shallow water, where the compounds would stun or kill the fish, allowing for easier capture. <ref name=Nelson /><ref name=Dale /> They then boiled and drained (leached) the fish at least three times to dilute the toxin's effects.<ref name = fish /> New shoots from the seeds also have been known to kill grazing cattle.<ref name = plants />

In Britain, the fruit are often called '''conkers''' because of their link to the game of conkers, played with the seeds.

==Cultivation== The most familiar member of the genus worldwide is the common horse-chestnut, ''Aesculus hippocastanum''. The yellow buckeye, ''Aesculus flava'' (syn. ''A.&nbsp;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 ornamental plants, and several horticultural hybrids have also been developed, most notably the red horse-chestnut ''Aesculus'' × ''carnea'', a hybrid between ''A. hippocastanum'' and ''A.&nbsp;pavia''.

==In history== The horse-chestnut ''A. hippocastanum'' was unknown to botanical science until 1596, when the Dutch botanist Carolus Clusius was given foliage and flowers in Vienna; it was then introduced further west, with the first plants reaching France in 1603, and Britain between 1612–1615.<ref name="Mitchell">{{cite book | last1=Mitchell | first1=Alan F. |chapter=Horse-chestnut |title=Alan Mitchell's Trees of Britain | publisher=Whitman Publishing & Distribution Company | date=1996 | isbn=0-00-219972-6 | pages=193–196}}</ref>

In Geneva, Switzerland, an official chestnut tree is used to indicate the beginning of the Spring; every year since 1818, the tree is observed by the secretary of the Grand Council of Geneva (the local parliament), and the opening of the first leaf is recorded and announced publicly. Over the years, four different horse chestnut trees have been used for these recordings.

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".<ref name=carnival />

The leaf of ''Aesculus'' was the official symbol of Kyiv on its coat of arms used from 1969 to 1995.<ref name="7253616chestnutKyivE"/> It remains an official symbol of Kyiv to this day.<ref name=7253616chestnutKyivE />

== See also == * Anne Frank tree

==References== === Explanatory notes === {{Notelist}}

=== Citations === {{Reflist|refs= <ref name=7253616chestnutKyivE>[https://www.pravda.com.ua/articles/2020/05/29/7253616/ {{"'}}Thujoy Khreshchatyk'. Why Kyivans miss chestnuts and how they became a symbol of the capital"], ''Ukrayinska Pravda'' (29 May 2019) {{in lang|uk}}</ref> <ref name=carnival>[https://books.google.com/books?id=SAxmDAAAQBAJ&pg=PT153 ''Carnival Campaign: How the Rollicking 1840 Campaign of "Tippecanoe and Tyler Too" Changed Presidential Elections Forever''], by Ronald Shafer, 2016</ref> <ref name = hardin1957a>Hardin, JW. 1957. A revision of the American Hippocastanaceae I. ''Brittonia'' 9:145-171.</ref> <ref name = hardin1957b>Hardin, JW. 1957. A revision of the American Hippocastanaceae II. ''Brittonia'' 9:173-195.</ref> <ref name = hardin1960>Hardin, JW. 1960. A revision of the American Hippocastanaceae III, Species of the Old World. ''Brittonia'' 12:26-38.</ref> <ref name=Harlan>{{cite book |last=Harlan |first=Jack R. |title=The Living Fields: Our Agricultural Heritage |year=1995 |publisher=Cambridge Univ. Press |location=Cambridge [u.a.] |isbn=978-0-521-40112-8 |edition=1. publ. |page=15}}</ref> <ref name=Akazawa>{{cite book |last1=Akazawa |first1=T. |last2=Aikens |first2=C.M. |title=Prehistoric Hunter-Gathers in Japan |date=1986 |publisher=University of Tokyo Press}}</ref> <ref name=Aikens>{{cite book |last1=Aikens |first1=C.M. |last2=Higachi |first2=T. |title=Prehistory of Japan |date=1982 |publisher=New York Academic Press}}</ref> <ref name=Hall>{{cite book |last=Hall |first=Alan |date=1976 |title=The Wild Food Trail Guide |edition=second |publisher=Holt, Rhinehart and Winston |location=New York |page=214}}</ref> <ref name=Peterson>{{cite book |last=Peterson |first=Lee |date=1977 |title=A field guide to edible wild plants of eastern and central North America |publisher=Houghton Mifflin Co. |location=Boston |pages=172}}</ref> <ref name=Nelson>{{cite book |last=Nelson |first=Guy |date=2006 |title=Ohio Buckeye (''Aesculus glabra'' Willd.), Plant Guide |publisher=US Department of Agriculture, Natural Resources Conservation Service |location=Washington, D.C.}}</ref> <ref name=Dale>{{cite book |last1=Dale |first1=Thomas R. |first2=Dixie B. |last2=Scogin |date=1988 |title=100 woody plants of Louisiana |publisher=The Herbarium of Northeast Louisiana University |location=Monroe, Louisiana |pages=118}}</ref> <ref name = fish>[https://www.primitiveways.com/fish_poison.html Fishing with Poisons]</ref> <ref name=Judd>{{cite journal |last1=Judd |first1=W.S. |first2=R.W. |last2=Sanders |first3=M.J. |last3=Donoghue |date=1994 |title=Angiosperm family pairs |journal=Harvard Papers in Botany |volume=1 |pages=1–51}}</ref> <ref name = hardin1957c>Hardin, JW. 1957. A revision of the American Hippocastanaceae I. Brittonia 9:145-171.</ref> <ref name = plants>[https://csuvth.colostate.edu/poisonous_plants/Plants/Details/51 Guide to Poisonous Plants]</ref> <ref name=phylogenetic>{{cite journal |last=Harrington |first=Mark G. |author2=Edwards, Karen J. |author3=Johnson, Sheila A. |author4=Chase, Mark W. |author5=Gadek, Paul A. |title=Phylogenetic inference in Sapindaceae sensu lato using plastid matK and rbcL DNA sequences |journal=Systematic Botany |date=Apr–Jun 2005 |volume=30 |issue=2 |jstor=25064067 |pages=366–382 |doi=10.1600/0363644054223549 |s2cid=85868684}}</ref> }}

==External links== {{Commons category}}

* [https://web.archive.org/web/20090115050608/http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?245 Germplasm Resources Information Network: ''Aesculus''] * Forest, F., Drouin, J. N., Charest, R., Brouillet, L., & Bruneau A. (2001). [https://www.researchgate.net/publication/237154605_A_morphological_phylogenetic_analysis_of_Aesculus_L_and_Billia_Peyr_Sapindaceae "A morphological phylogenetic analysis of Aesculus L. and Billia Peyr. (Sapindaceae)"]. ''Can. J. Bot.'' 79 (2): 154–169. {{doi|10.1139/b00-146}}. * [https://www.henriettes-herb.com/eclectic/kings/aesculus.html ''Aesculus glabra'' (Ohio buckeye)] King's American Dispensatory * [https://web.archive.org/web/20090303131928/http://www.portraitoftheearth.com/trees/horsechestnut.html Winter ID pictures]

{{Taxonbar|from=Q158752}} {{Authority control}}

Category:Aesculus Category:Sapindaceae genera Category:Botanical taxa named by Carl Linnaeus