Bidens hyperborea (common names estuary beggarticks, northern beggarticks,[1] or estuary bur-marigold[2]) is a variable species of flowering plant in the family Asteraceae, known from estuarine regions in northeastern North America. It is similar to Bidens cernua, Bidens laevis, and Bidens eatonii. B. hyperborea is listed as an endangered species in the state of Massachusetts, where it is threatened by habitat degradation,[3] and is listed by NatureServe as critically imperiled (S1) in the province of Ontario and possibly extirpated from New Hampshire.
Bidens hyperborea is an annual herb, growing up to 70 cm (28 inches) tall. It produces yellow flower heads, sometimes one at a time, sometimes 2 or 3, each containing both disc florets and (usually) ray florets. The species grows in salt marshes and along the banks of marine estuaries.[4] [5]
Bidens hyperborea was first described by Edward Lee Greene in 1901 based on specimens by James Melville Macoun collected at James Bay, originally identified as Bidens cernua. In 1915, Meritt Lyndon Fernald and Harold St. John described Bidens colpophila from specimens collected near the mouth of the Kennebec River, noting its similarities to Greene's B. hyperborea but distinguishing it based on characteristics of the achenes.[6]
A subsequent 1918 review by Fernald concluded that B. hyperborea and B. colpophila were conspecific, but the variability of the species in numerous isolated localities led to the circumscription of a number of varieties, distinguished by the length of the achenes, leaf morphology, and growth habit. In 1925, Norman Carter Fassett described two new varieties, var. laurentiana and var. svensonii, separating them based on their leaf morphology and involucral bracts. Fassett also described an interspecific hybrid of B. hyperborea and B. cernua.[7]
Most authorities currently do not recognize the varieties of B. hyperborea and treat it without subspecific divisions.
It grows along the coasts of Hudson Bay, the Arctic Ocean, and the North Atlantic Ocean in eastern Canada (Labrador,[8] Nunavut, Ontario, Quebec, New Brunswick, Nova Scotia) and the northeastern United States (Maine, New Hampshire, Massachusetts, New York).[9]
