Fabaceae : Thermopsis rhombifolia
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Family Name
Fabaceae
Common Name
Goldenpea, Prairie thermopsis
Native American Name
Lakota: waȟpé sóta
Description
Thermopsis rhombifolia is a perennial rhizomatous herb, with 1 to several ascending to erect stems, 15–60 cm tall, with or without a covering of short, stiff hairs. This species is often colony forming in open prairies. The alternate, palmately trifoliate leaves have leaflets that are ovate, 15–50 mm long and 10-20 mm wide, with a few to many appressed hairs. The inflorescence consists of subterminal racemes, 3–10 cm long. The calyx forms a hairy, bilabiate tube, 4-5 mm long, the upper lip having 2 united teeth, 3-4 mm long , and the lower lip with 3 teeth 2-3 mm long. The papilionaceous corolla has yellow petals, the banner often has purple spots and is 17-22 mm long, the wings are 15- 18 mm long, and the oblong keel is 14-16 mm long. The flowers have 10 separate stamens. The fruit is a legume, 3–8 cm long with 3 to 10 seeds, constricted between the ~5 mm long seeds. Goldenpea blooms from April into June on open prairies, hillsides and woodlands in western South Dakota.
Horticulture Notes
Seed Collection: Collect seed in July-September, after the pods dry and the seeds turn dark brown.
Germination: the seedcoat enforces dormancy. Chip the seedcoat with the tip of a small sharp knife before planting. Can be sown in fall or spring.
Vegetative Propagation: New plants arise from the rhizomes and can be separated and transplanted.
Soils: Tolerates most well drained soil types, but does best in loamy soils.
Light: Full sun to light shade.
Water: Moderate to moist but has some drought tolerance
Additional Notes
Goldenpea plants have bright yellow flowers that add color to a native plant garden. They are easy to grow and will spread to fill in open areas. The flowers provide nectar for butterflies and pollen for native bees. The flowers are also a source of a natural yellow dye.