Two-Grooved Milkvetch
Two-Grooved Milkvetch, Two-Grooved Poisonvetch
[Astragalus bisulcatus (Hook.) A. Gray]
Fabaceae (Legume Family)
Mature flowering plant, with fruit pods ▼ ▲
flowers ▼ ▲
flowers ▼ ▲
stem with fruit, and close-up of fruit pods below ▼ ▲
post-flowering plant loaded with pods ▲
Two-Groove Milkvetch (Two-Groove Poisonvetch) is a simple, perennial native to the central and northern prairies and rangeland, particularly alkaline or high-selenium soils. More plants will be found in disturbed or over-grazed areas in these regions, as well.
The entire plant (not just flowers) has a unique, characteristic, strong musky odor (similar to alkali poisonvetch) that is evident when they are nearby. The plant tends to have an upright-ascending branching pattern, with several branches arising from a simple perennial tap root. Stems may be green or reddish, with hairy, pinnately-compound leaves with oval leaflets. They have upright racemes of showy pinkish-purple to rose-purple flowers in late spring to early summer, followed by slender, grooved pods, with two-grooves along the midveins (hence their name).
Two-groove milkvetch appears very similar to alkali poisonvetch, and can be distinguished by the deeply grooved pods (in two-groove milkvetch) and different stipule and sepal characteristics. Alkali poisonvetch will tend to have white to pale-purple flowers, while two-groove milkvetch will usually have purplish or rose-purple flowers, but there is overlap in flower color for both species.
Consumption of two-groove milkvetch can cause selenium toxicity in grazing animals. This plant usually will not be grazed if more desirable vegetation is available.