Fabaceae FAMILY

Thermopsis montana

Edibility

0/5

Medicinal

2/5

Safety & Hazards

The plant contains alkaloids which are especially toxic in young plants and in mature flowering plants. Children suffered digestive tract problems, weakness and neurological effects after eating a few seeds or flowers^[1]. All parts of the plant are toxic. Ingesting 0.6 to 2.8g of dry foliage per kg of body weight for several days produces severe muscle degeneration in cattle. Ingesting 300 - 400g of dried plant material for 3 - 4 days will severely intoxicate cattle and slightly more can be lethal^[1].

Cultivation Details

HabitPerennial

Growth—

Thermopsis montana is a very cold-hardy plant, able to tolerate temperatures down to around -30°c when fully dormant^[2]. Grows best in a sunny position, preferring a moist, well-drained, sandy to loam soil^[1]. Prefers a pH in the range 6.6 - 8.5^[1]. Plants can spread fairly rapidly by means of rhizomes, and can out-compete less vigorous plants^[2]. This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby^[3].

Propagation

Seed - it has a hard seedcoat and may benefit from scarification before sowing in order to speed up and improve germination^[1]. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Thermopsis+montana>

Pollinators

Bees

References

[1]Plants Database — United States Department of Agriculture · http://plants.usda.gov/java/factSheet ↩︎An online database with an excellent collection of fact sheets about native N. American plants.
[2]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
[3]Nodulation Plants in GRIN Taxonomy — United States Department of Agriculture · http://www.ars-grin.gov/~sbmljw/cgi-bin/taxnodul.pl?language=en ↩︎An online database listing plants that have either positive or negative reports on root and stem nodulation with nitrogen-fixing bacteria.
[4]Annals of the Missouri Botanical Garden Vol. 81 — Missouri Botanical Garden; St. Louis. · 1994 · http://www.biodiversitylibrary.org/ · ISBN 0026-6493 ↩︎A botanical journal with various articles, including a revision of the genus Petrea. It can be downloaded from the Internet.