This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Herbs or rarely shrubs, those in general cultivation with digitate leaves. Stipules adnate to the petiole. Flowers showy, white, yellow, crimson, or scarlet. Calyx with 5 or 4 bracteoles, and as many sepals, valvate in bud. Petals of the same number. Stamens many. Styles not elongating after flowering. About 120 species, nearly all within the north temperate zone, a few on the mountains of the tropics, and two in the south. So named from potens, powerful, effective, from their reputed medicinal properties.
1. P. atrosanguinea. - A hairy branching herbaceous plant about 2 feet high with petiolate digitately trifoliolate leaves; leaflets obovate, serrate, with a silvery tomentum beneath. Flowers 1 1/2 to 2 inches in diameter, dark crimson. A native of Nepal, blossoming from May to July.
2. P. Nepalensis of Hooker, not of Don (P. formdsa of Don). - Very much like the foregoing, but with quinate radical leaves. There are several handsome varieties of these two species in cultivation, either of hybrid origin or from natural variation. Russelliana, insignis, Menziesii, striata, and many others; some with double yellow and crimson flowers.
There are many yellow and white flowered species. P. splen-dens, with silvery foliage, and P. Pyrenaica, with yellow flowers; and P. rupestris and P. alba, with white flowers, are amongst the best. P. fruticosa is an indigenous shrub 2 to 4 feet high with 3- to 5-foliolate leaves and yellow flowers.