Asarum

Asarum
Asarum caudatum (western wild ginger)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Magnoliids
Order:	Piperales
Family:	Aristolochiaceae
Genus:	Asarum
Species
See text

Asarum (Á-sa-rum) is a genus of plants in the birthwort family Aristolochiaceae, commonly known as Wild ginger.

Description

Asarum is a genus of low-growing herbs distributed across the temperate zones of the northern hemisphere, with most species in East Asia (China, Japan and Vietnam) and North America, and one species in Europe. Biogeographically, Asarum originated in Asia

They have characteristic kidney-shaped leaves, growing from creeping rhizomes, and bear small, axillary brown or reddish flowers.

The plant is called wild ginger because the rhizome tastes and smells similar to ginger root, but the two are not particularly related. The root can be used as a spice, but is a potent diuretic. Asarum canadense and other species in the genus contain the nephrotoxic rodent carcinogen aristolochic acid, which the FDA warns against consuming.^{[1][2] [3]} The birthwort family also contains the genus Aristolochia, known for carcinogens.

Wild ginger favors moist, shaded sites with humus-rich soil. The deciduous, heart-shaped leaves are opposite, and borne from the rhizome which lies just under the soil surface. Two leaves emerge each year from the growing tip. The curious jug-shaped flowers, which give the plant an alternate name, little jug, are borne singly in Spring between the leaf bases.

Wild ginger can easily be grown in a shade garden, and makes an attractive groundcover.

Asarum europaeum flower

Taxonomy

Traditionally the genus Asarum was considered as a single genus with about 85 species. However there has been a trend among botanists to segregate the genus into separate genera, based on considerations of chromosome number and floral morphology :

• Asarum s.s. (about 17 species), distributed in Asia (mainly China), North America and Europe
• Heterotropa ( about 50 species), distributed in Asia
• Asiasarum (3 to 4 species), distributed in Asia
• Geotaenium (3 to 4 species), distributed in Asia
• Hexastylis ( 10 species), distributed in North America

Study of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA, combined with morphological data, have yielded a better-resolved phylogenetic hypothesis, confirming the distinctiveness of the above-named genera.^[4]

• Asarum s.s. : the North American species are monophyletic and are derived from within the paraphyletic Asian species group.
• Geotaenium is a sister to Asarum s.s., showing its close relationship to Asarum s.s.
• Asiasarum is a sister to the Hexastylis + Heterotropa clade, showing several synapomorphies with this clade
• Hexastylis : this genus has been recognized solely on the study by H.L. Blomquist.^[5] However the above-mentioned DNA study provided indications that Hexastylis is not monophyletic and that some species of Hexastylis are more closely related to Asiatic species of Heterotropa than they are to other species of Hexastylis.
• Heterotropa : this is a complex monophyletic group, well nested within the Asiasarum + Hexastylis + Heterotropa clade

However, many botanists still treat these segregated genera as sections of Asarum s.l., especially Hexastylis ^[6]

Species

See also

• Hexastylis, a closely related genus sometimes treated as synonymous with Asarum

External links

Wikispecies has information related to: Asarum

Wikimedia Commons has media related to: Asarum

• Takashi Sugawara (1982). "Taxonomic studies of Asarum sensu lato". Journal of Plant research 95 (3): 295–302. http://www.springerlink.com/content/m1m8585288p32671/. 
• Lawrence M. Kelly (2001). "Taxonomy of Asarum Section Asarum (Aristolochiaceae)". Systematic Botany 26 (1): 17–53. doi:10.1043/0363-6445-26.1.17 (inactive 2009-10-29). http://www.bioone.org/doi/abs/10.1043/0363-6445-26.1.17. 
• List of Asarum species
• The International Agency for Research on Cancer.

References