This sample was brought into us out of curiosity. A very large patch is growing in a field where cattle will be turned out. The plant is known as Thermopsis rhombifolia and is from the pea family. You may recognize a similarity between the sweet pea flower and this plant. It is considered native and is a perennial. It is considered a weed and can be highly competitive with other vegetation.
It has several distiguishing characteristics. It is 6- 16 inches tall and has from 1-5 stems emerging from the same crown. Stems contain leaflets that occur in threes and alternate. Flowers cluster up to 4 inches long and contain 10-30 individual yellow flowers. Usually flowers in April and May but this flowering sample was brought into us in July (2016). It is not palatable to livestock.
Other names: Goldenpea, Prairie Buckbean, Prairie Thermopsis, Prairie Goldenpea, Golden Bean, Yellow Bean, Yellow Pea, False Lupine
Reference book: Weeds of the West – digital page 55, paper version page 344