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..
Perennial branching herbs, with sheathing scales at the base, alternate 3-foliolate leaves, and large yellow or purple flowers in terminal or axillary racemes. Stipules usually large and foliaceous. Calyx campanulate or short-turbinate, its lobes equal and separate, or the two upper ones united. Standard nearly orbicular, equalling the oblong wings and about equalling the keel. Stamens 10, incurved, separate. Ovary sessile or short-stipitate; ovules ∞; style slightly incurved; stigma terminal, small. Pod sessile or short-stalked, flat (in our species), linear or oblong, straight or curved. [Greek, Lupine-like.]
About 20 species, natives of North America and northern and eastern Asia. Besides the following, some 10 others occur in the southern Alleghanies and in the western part of the continent. Type species: Thermopsis lanceolata (Willd.) R. Br.
Leaflets l' - 3' long; panicle elongated, usually long-peduncled; eastern.
Leaflets 1/2'-1 1/2' long; panicle short, short-peduncled; western.
Podalyria mollis Michx. Fl. Bor. Am. 1: 264. 1803.
Baptisia mollis DC. Prodr. 2: 100. 1825.
Erect, somewhat divaricately branched, 2°-3° high, finely appressed-pubescent. Leaves petioled, 3-foliolate; leaflets oval, rhombic-elliptic or obovate, entire, 1'-3' long, 9"-15" wide, obtuse or acute, nearly sessile; stipules ovate or lanceolate, shorter than the petiole; racemes 6'-10' long, mainly terminal; pedicels 2"-6" long, bracted at the base; flowers yellow, about 9" long; pod short-stalked in the calyx, linear, slightly curved, 2-4' long.
Cytisus rhombifolius Nutt. Fraser's Cat. 1813. Thermia rhombifolia Nutt. Gen. 1: 282. 1818.
Erect, 8'-20' high, branched, appressed silky-pubescent. Leaves petioled; leaflets' oval or obo-vate or rhombic-elliptic, obtuse, entire, 1/2'-1 1/2' long, 3"-6" wide, sessile; stipules broad; racemes terminal or lateral, rather dense, few-flowered, 2'-5' long; pedicels 2"-4" long, bracted; flowers yellow, about 10" long; pod linear, generally strongly recurved-spreading, several-seeded, stalked in the calyx, 3'-4' long.
In sandy soil, on plains and hills, North Dakota to Nebraska. Kansas, Saskatchewan, Montana and Colorado. Yellow or bush-pea. June-July.