Asarum, commonly known as wild ginger or little jug, is a genus of approximately 138 low-growing perennial herbs in the family Aristolochiaceae (the pipevine family), order Piperales. The plants grow from creeping underground rhizomes and typically reach no more than 20 cm in height. Their paired leaves are kidney-shaped to heart-shaped, often evergreen, and form a dense mat that makes the genus attractive as a woodland groundcover.
The flowers are small and jug-, urn-, or bell-shaped, brownish to purplish in colour, and bloom in spring largely concealed beneath the foliage close to the ground. They are malodorous and pollinated by flies. Despite the common name, Asarum is not related to true ginger (Zingiber officinale); the name reflects the similar spicy scent and taste of the rhizomes and leaves rather than any botanical affinity.
The genus is distributed across the temperate Northern Hemisphere, with the greatest diversity in East Asia — particularly China, Japan, and Vietnam — and a secondary centre in North America. One species, Asarum europaeum, is native to Europe. Biogeographically the group is thought to have originated in Asia.
Warning: The FDA warns against consuming Asarum. The plants contain aristolochic acid, a potent nephrotoxin and carcinogen. Leaves and roots are poisonous to humans and should not be ingested.
Etymology
The genus name Asarum derives from the ancient Greek word ἄσαρον (asaron), which was the classical name applied to Asarum europaeum, the sole European representative of the genus. The name was formalised by Carl Linnaeus in Species Plantarum (1753), where he placed it at page 442. The English common name "wild ginger" alludes to the ginger-like scent and flavour of the rhizomes, while "little jug" refers directly to the shape of the flowers.
Distribution
Asarum is distributed across the temperate Northern Hemisphere. The greatest species richness occurs in East Asia — principally China, Japan, and Vietnam — with a secondary centre of diversity in North America. In North America the native range extends broadly from the southeastern states (Virginia to Louisiana) northward into the upper Midwest (Alabama to Wisconsin). One species, Asarum europaeum, is indigenous to Europe and is also recorded as introduced in Denmark, Great Britain, the Netherlands, and Norway. In Switzerland, Info Flora recognises Asarum europaeum and two subspecies (subsp. europaeum and subsp. caucasicum). Most species favour upland deciduous and mixed deciduous-conifer forests from sea level to approximately 600 m elevation.
Taxonomy
Asarum L. (IPNI urn:lsid:ipni.org:names:3127-1) is accepted in family Aristolochiaceae, order Piperales, class Magnoliidae — a clade of early-diverging flowering plants. POWO and NCSU both recognise approximately 137–138 accepted species; the GBIF backbone catalogues 201–265 descendant taxa across all ranks.
Four heterotypic synonyms have been placed in synonymy under Asarum by POWO: Asiasarum F.Maek., Heterotropa C.Morren & Decne., Hexastylis Raf., and Japonasarum Nakai. These segregate genera were proposed primarily on the basis of Asian and North American morphological variants but are not currently maintained as distinct by most authorities.
Ecology
Asarum species occupy moist, shaded forest floors with humus-rich, well-drained acidic soils. They naturalise readily by spreading via creeping rhizomes, forming low dense mats. The flowers are small, produced close to the ground, and are pollinated by flies attracted to their malodorous scent — a strategy common in early-spring woodland plants where bee activity is limited. The plants are naturally deer-resistant.
Cultivation
Wild gingers are valued shade-garden plants, principally grown as evergreen groundcovers beneath trees and in woodland settings. They thrive in moist, fertile, acidic soil in deep to partial shade (tolerating as little as dappled light and up to 6 hours of direct sun). Soil texture can be light, medium, or heavy provided moisture is adequate. Growth rate is medium and maintenance requirements are low once established.
USDA cold-hardiness spans approximately zones 4a–8b, with tolerance to at least -15°C. Suitable landscape applications include mass plantings, border edging, rock gardens, native plantings, and container culture. Slugs, snails, and rust are occasional pest concerns but the genus is generally robust.
Propagation
Asarum is propagated by two main methods. Division is carried out in spring or autumn; the plants are slow to increase and spreading clumps should be divided carefully. Seed can be sown fresh into a cold frame immediately after ripening; if seeds have been stored they require a period of cold stratification before germination. Plants raised from seed take longer to establish than divisions.
Uses & Cautions
Several Asarum species have a history of medicinal and aromatic use. The root of some species is recorded as stomachic — aiding digestive function. An essential oil with a sassafras-like fragrance can be extracted from the plants. However, the FDA explicitly warns against ingesting any part of Asarum: the plants contain aristolochic acid, which is both nephrotoxic (damaging to the kidneys) and a known carcinogen. At least three species carry documented reports of toxic leaves.
