Astragalus bisulcatus variety haydenianus.  Synonym: Astragalus haydenianus. (Hayden's Milkvetch)
Fabaceae (Pea Family)

Above: Near Lone Mesa State Park, June 15, 2016.
Left: Foothills, montane. Meadows, roadsides. Spring, summer.
Near Lone Mesa State Park, June 11, 2008.

Astragalus bisulcatus variety haydenianus can be abundant in masses, especially along roadsides in the lower montane region.  It has quite small individual flowers but the flowers are so numerous that clustered together they are very showy. The inflorescence has a distinctive vertical growth pattern, but the leaves arch. Lower stems are often tinged red. 

The plant often prefers selenium rich soils of Mancos Shale and commonly has the characteristic selenium odor.

Asa Gray named this species in 1876 from a specimen collected by Townshend Brandegee on the 1874 Hayden Survey in the La Plata Mountains (between present day Durango and Mancos, Colorado).  William Weber calls this plant "Astragalus haydenianus".  Kartesz, Welsh, and the authors of Intermountain Flora call it "Astragalus bisulcatus variety haydenianus".

Flower keel tips are purple spotted; the calyx tube surrounding the base of each flower has black, appressed hairs; and flower stems are packed with numerous tiny flowers about 8 millimeters in total length.

Foothills, montane. Meadows, roadsides. Spring, summer.
Along Highway 184, June 17, 2010 and Lone Mesa State Park, August 4, 2008.

Pods are hairy, flattened, 6-9 millimeters long, and pendulous.  One side of the pod has a slightly raised keel along the suture line and the other side has a very prominent keel.  The keel is evident even in young green pods.  (Instead of indicating that the pod has a keel, we could say that the pod has two indentations (bi-sulcate) on either side of the suture).

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Questionable presence

Range map for Astragalus bisulcatus

Range map for Astragalus bisulcatus variety haydenianus