name = Buckthorn
image_width = 240px
image_caption = Alder Buckthorn ("Rhamnus frangula")
divisio = Magnoliophyta
genus = "Rhamnus"
genus_authority = L.
subdivision_ranks = Species
subdivision = See text.
:"For the genus "Hippophae", see
The Buckthorns ("Rhamnus") are a genus (or two genera, if "Frangula" is treated as distinct) of about 100 species of
shrubs or small trees from 1-10 m tall (rarely to 15 m), in the buckthorn family Rhamnaceae. They are native throughout the temperate and subtropical Northern Hemisphere, and also more locally in the subtropical Southern Hemispherein parts of Africaand South America.
deciduousand evergreenspecies occur. The leaves are simple, 3-15 cm long, and arranged either alternately or in opposite pairs. One distinctive character of many buckthorns is the way the veination curves upward towards the tip of the leaf. The plant bears fruits which are dark blue berries. The name is due to the woody spine on the end of each twig in many species. Buckthorns are used as food plants by the larvae of some Lepidopteraspecies – see list of Lepidoptera that feed on buckthorns.
The genus is divided into two subgenera, sometimes treated as separate genera:
*Subgenus "Rhamnus": flowers with four petals, buds with bud scales, leaves opposite or alternate, branches with spines. Species include:
Rhamnus alaternus" – Italian Buckthorn
Rhamnus alnifolia" – Alderleaf Buckthorn
Rhamnus arguta" – Sharp-tooth Buckthorn
Rhamnus cathartica" – Common (or Purging) Buckthorn (syn. "R. catharticus")
Rhamnus crocea" – Redberry Buckthorn (ssp. "crocea"), Hollyleaf Buckthorn (ssp. "pilosa")
Rhamnus davurica" – Dahurian Buckthorn
Rhamnus globosa" – Lokao Buckthorn
Rhamnus ilicifolia" – Hollyleaf Redberry
Rhamnus japonica" – Japanese Buckthorn
Rhamnus lanceolata" – Lanceleaf Buckthorn
Rhamnus pirifolia" – Island Redberry Buckthorn
Rhamnus prinoides" – Shiny-leaf Buckthorn
Rhamnus saxatilis" – Rock Buckthorn, Avignon Buckthorn, Avignon Berry (syn. "R. infectoria", "R. infectorius")
Rhamnus serrata" – Sawleaf Buckthorn
Rhamnus smithii" – Smith's Buckthorn
Rhamnus staddo" – Staddo (syn. "R. rhodesicus")
Rhamnus tinctoria" - Dyer's Buckthorn (syn. "R. saxatilis" ssp. "tinctorius")
Rhamnus utilis" – Chinese Buckthorn
*Subgenus "Frangula": flowers with five petals, buds without bud scales, leaves always alternate, branches without spines. Species include:
Rhamnus betulaefolia" ("Frangula betulifolia") – Birchleaf Buckthorn
Rhamnus californica" ("Frangula californica") – California Buckthorn, Coffeeberry
Rhamnus caroliniana" ("Frangula caroliniana") – Carolina Buckthorn, Indian Cherry (syn. "R. carolinianus")
Rhamnus frangula" ("Frangula alnus") – Alder Buckthorn, Glossy or Breaking Buckthorn, Black Dogwood
Rhamnus glandulosa" - Sanguinho
Rhamnus latifolia" ("Frangula azorica")
Rhamnus purshiana" ("Frangula purshiana") – Cascara Buckthorn (syn. "R. purshianus")
Rhamnus rubra" ("Frangula rubra") – Red Buckthorn
Rhamnus sphaerosperma" ("Frangula sphaerosperma") – West Indian Buckthorn
The Purging Buckthorn or Common Buckthorn ("R. cathartica") is a widespread
European native species, in the past used as a purgative, though its toxicity makes this a very risky herbal medicineand it is no longer used. Introduced into the United Statesas a gardenshrub, this has become an invasive speciesin many areas there. It has recently been discovered to be a primary host of the soybean aphid"Aphis glycines", a problem pest for soybeanfarmers across the US. The aphids use the buckthorn as a host for the winter and then spread to nearby soybean fields in the spring.
Another European species, Alder Buckthorn ("R. frangula", syn. "Frangula alnus") was of major
militaryimportance in the 15th to 19th centuries, as its woodprovided the best quality charcoalfor gunpowdermanufacture.
Italian Buckthorn ("R. alaternus"), an evergreen species from the Mediterranean region, has become a serious weed in some parts of
New Zealand—especially on Hauraki Gulfislands.
Dyer's Buckthorn ("R. tinctoria") is used, together with the
Asian Chinese Buckthorn ("R. utilis"), to produce the dye"china green". Another species, Avignon Buckthorn ("R. saxatilis") provides the yellow dye Persian berry, made from the berries.
Sanguinho "(R. glandulosa)" is endemic to the
Macaronesian islands, where it is found in the " laurisilva" forests of the Madeira and Canary Islands.
North American species include Alder-leaf Buckthorn ("R. alnifolia") right across the continent, Carolina Buckthorn ("R. (F.) caroliniana") in the east, Cascara Buckthorn ("R. (F.) purshiana") in the west, and the evergreen California Buckthorn or Coffeeberry ("R. (F.) californica") and Hollyleaf Buckthorn ("R. crocea") in the west.
In South America, "Rhamnus diffusus" is a small shrub native from the
Valdivian temperate rain forestsin Chile.
Buckthorns may be confused with
Dogwoods, which share the curved leaf venation; indeed, "dogwood" is a local name for "R. prinoides" in southern Africa, a plant used to make Ethiopian meadand known as "gesho" in Ethiopia. The two plants are easy to distinguish by slowly pulling a leaf apart; in dogwood thin white latex strings can be seen, strings not present in buckthorn.
* [http://www.ajol.info/viewarticle.php?id=17292&jid=68&layout=abstract Scientific chemical research on African Rhamnus]
* [http://www.chilebosque.cl/shrb/rdiff.html "Rhamnus diffusus" pictures from "Chilebosque"]
* [http://www.cas.vanderbilt.edu/bioimages/species/frame/frca13.htm "Frangula caroliniana" images at bioimages.vanderbilt.edu]
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