This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Shrubs with firm unequally pinnate leaves, scarious sheathing stipules, and large mostly yellow flowers. Calyx-tube saucer-shaped. Bractlets, calyx-lobes and petals 5. Petals rounded, not clawed. Stamens about 25, in 5 clusters around the hemispheric receptacle; filaments filiform; anthers flat. Pistils numerous on the receptacle; style club-shaped, glandular above, lateral; stigmas lobed. Achenes densely covered with long straight hairs. Seeds amphitropous, ascending. [Greek, bearing hairs, referring to the hairy achenes and receptacle.]
About five species, natives of the north temperate and arctic zones. Only the following typical one occurs in North America.
Shrubby, much branched, stems erect or ascending, very leafy, 6'-40 high, the bark shreddy. Stipules ovate-lanceolate, membranous, acute or acuminate, entire; leaflets 5-7, oblong, linear-oblong, or somewhat oblanceolate, entire, acute or acutish at each end, 6"-12" long, silky-pubescent, the margins revolute; flowers terminal, densely cymose, or solitary, bright yellow, 8"-15" broad; petals nearly orbicular, exceeding the ovate calyx-lobes and bractlets; stamens 15-20; style lateral, filiform; achenes, disk and receptacle long-hairy.
In swamps or moist rocky places, Labrador and Greenland to Alaska, south to New Jersey, Illinois, Minnesota, in the Rocky Mountains to Arizona, and in the Sierra Nevada to California. Also in northern Europe and Asia. Called also hardhack and prairie weed. A troublesome bushy weed in northern New England. June-Sept.