Polanisia is a small genus of annual flowering plants in the family Cleomaceae, the spider-flower family, which is closely related to Brassicaceae (the mustard family). The genus contains five recognized species, all native to North America and Mexico, and is commonly known as clammyweeds — a name that reflects the sticky, glandular hairs that cover the stems and leaves of these plants. These hairs produce a pungent, resinous scent, characteristic of the group.
Members of Polanisia are herbaceous annuals with alternate, palmately compound leaves typically divided into three leaflets. The flowers are small and four-petalled, usually white to pale pink or purplish, and are borne in terminal racemes. The stamens are notably numerous, a feature reflected in the most widespread species name, Polanisia dodecandra ("twelve-stamened"). The fruit is a narrow, elongated capsule.
The most common species, Polanisia dodecandra (redwhisker clammyweed), is widespread across much of North America, growing in disturbed habitats, sandy soils, roadsides, and riverbanks. Polanisia erosa (large clammyweed) and Polanisia tenuifolia (slenderleaf clammyweed) occupy drier, more restricted ranges. Polanisia jamesii (James' clammyweed) is of conservation concern, listed as locally endangered in Minnesota. Polanisia uniglandulosa (Mexican clammyweed) extends the genus's range into Mexico.
Etymology
The name Polanisia derives from the Greek words polys (many) and anisos (unequal), referring to the unequal or numerous stamens characteristic of the flowers in this genus. The common name "clammyweed" refers to the sticky, glandular hairs that coat the plants.
Distribution
Polanisia species are native to North America, ranging from Canada south through the United States to Mexico. Polanisia dodecandra is the most widespread, found across much of the continent in disturbed habitats, sandy soils, roadsides, and riparian areas. Polanisia uniglandulosa extends the genus into Mexico and Central America.
Ecology
Polanisia species typically grow in disturbed, open habitats including roadsides, riverbanks, sandy flats, and prairie margins. The sticky glandular hairs on the stems and leaves may deter herbivory and trap small insects, though the plants are primarily pollinated by bees attracted to their nectar. The aromatic foliage is unpalatable to most grazers.
