Common Name: two-grooved milkvetch
Type: Herbaceous perennial
Family: Fabaceae
Native Range: Central and western North America
Zone: 3 to 6
Height: 1.00 to 2.50 feet
Spread: 1.00 to 2.50 feet
Bloom Time: May to July
Bloom Description: Reddish-purple
Sun: Full sun
Water: Dry
Maintenance: Low
Suggested Use: Herb
Flower: Showy
Attracts: Butterflies
Tolerate: Deer, Clay Soil, Dry Soil
Culture
Best grown in dry, alkaline soils in full sun. Tolerant of clay soils. Hardy in Zones 3-6.
Noteworthy Characteristics
Astragalus bisulcatus, commonly called two-grooved milkvetch, is a shrubby, herbaceous perennial native to the Mountain West region of the United States from Montana and western North Dakota south to northern Arizona and New Mexico. It can be found growing in upland meadows, prairies, grasslands, and roadsides on dry, typically selenium-rich soils. Mature plants will reach 1-2.5' tall with an equal spread. The upright stems emerge from a branched, woody root-stock. The pinnately compound leaves have 8-13 pairs of 0.75" long, oblong to elliptic leaflets. Dense, 4-7" long, terminal flowering spikes emerge in late spring to mid-summer. The nodding, bright reddish-purple (occasionally white) flowers reach around 0.5" long and are followed by 0.75" long, narrowly oblong pod with two distinct grooves running lengthwise on their upper surface. The flowers are attractive to bumblebees and both a nectar and larval food source for several species of butterflies, including the gray hairstreak, orange sulfur and Persius duskywing.
The genus name Astragalus comes from Greek meaning "ankle bone". Various sources list this as reference to the appearance of the roots, seeds, or inflorescences.
The specific epithet bisulcatus means "having two furrows", in reference to the seed pods of this species.
The common name two-grooved milkvetch refers to the seed pods of this species.
Problems
This plant accumulates selenium in its tissues, which if consumed by livestock or humans can be toxic. No pest or disease issues of note. All parts of this plant have unpleasant, musky, sulfur odor.
Uses
Allow to naturalize in dry prairie plantings where browsing by livestock or other domesticated animals is not a concern.