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Bartonia paniculata (Michx.) Muhl.

Photo: Bartonia paniculata, Screwstem

Screwstem

Habitat: Wet peat and sand. [Coastal non-tidal wetland (non-forested, wetland)]

Range: Florida to Louisiana, north to southern New England and Nova Scotia, west through southern New York to Okalahoma.

Aids to Identification: The species is readily distinguished from Bartonia virginica (L.) BSP by alternate (rather than opposite) leaves below the inflorescense and a calyx that is cleft from 2/3 to nearly the base vs. lobed for B. virginica.

Ecological characteristics: Plants may be parasitic or hemiparasitic on the roots of other plants or trees.

Phenology: Flowers August to October. Tiny dust-like seeds are scattered in the wind in early autumn.

Family: Gentianaceae

Synonyms: Both the nominate subspecies and the subspecies iodandra (B.L. Robins.) J. Gillett are rare.

Known Distribution in Maine: This rare plant has been documented from a total of 6 town(s) in the following county(ies): Cumberland, Hancock, Knox, Sagadahoc, York.

Dates of documented observations are: 1893, 1917, 1990 (4), 1991 (8), 1998, 2001

Reason(s) for rarity: Typical variety at northern limit of range in Maine; subspecies iodandra disjunct from main population.

Conservation considerations: Little is known about this species's population biology. Maintaining the natural hydrology of the wetlands in which it occurs is prudent.