Thermopsis rhombifolia, also known as prairie thermopsis,golden bean, buffalo bean, wet tooth, and buffalo flower, is a hardy perennial native to the North Americanplains. 
A member of the pea family, it grows in grassland, hillsides, and patchy woodland areas to a height of about 30 cm, and produces bright yellow golden flowers about a centimetre long. The flowers were commonly used by the natives as a source of yellow dye and were boiled in a tea as a cure for stomach ailments for people and horses. The plant has toxic properties if ingested; symptoms of poisoning include vomiting, dizziness, and abdominal pain.
This plant is a beautiful addition to an early spring garden, but is extremely aggressive and must be contained.