Astragalus species are difficult to identify and it is the seed pod, not the flower, that is often crucial in the identification process.

     The common name, "Locoweed", is applied not to one plant but to many members of the Astragalus genus, for many of these plants absorb toxic soil substances, especially selenium, which cause grazing animals a variety of serious ailments.  Further complicating the common name: some people use the name "Locoweed" not only for Astragalus but also for another Pea genus, Oxytropis.  And, making common names even more confusing, many Astragalus also carry the common name of "Milk Vetch" (easily confused with other Peas known as "Vetch").  These common names are so confusing that they really should not be used (except in whispers to close friends). 

    The genus was named by Linnaeus in 1753 and the word "Astragalus" means "ankle bone" in Greek.  It is an ancient Greek plant name perhaps given because of  the seed shape in some members of the Astragalus genus or, the authors of Intermountain Flora conjecture, because the Greeks used rattling bones for dice and the sound made is similar to the rattling of dry Astragalus seeds in the pod.

Foothills, montane.  Meadows, woodland openings.  Spring, summer.
Ryman Creek Trail, June 14, 2011.

Astragalus tenellus is widespread in the Western United States and is found in a wide variety of habitats from Pinyon-Juniper to Spruce-Fir woodlands.  The plant can be from four to 20 inches tall and wide.  Flowers are tiny and numerous.

This plant was first collected for science by Meriwether Lewis "on the banks of the Missouri" and it received its first name, Ervum multiflorum, from Frederick Pursh in 1814.  Pursh renamed the plant Astragalus tenellus in 1817 and Asa Gray renamed the plant A. multiflorus.  John Kartesz (the ultimate authority for names on this web site) accepts Gray's name.

The Latin "ellus" means "small" and "tenner" means "soft, delicate".

Astragalus multiflorus. Synonym: Astragalus tenellus.
Fabaceae (Pea Family)

Foothills, montane.  Meadows, woodland openings.  Spring, summer.
Ryman Creek Trail, June 14, 2011.

Astragalus multiflorus. Synonym: Astragalus tenellus.
Fabaceae (Pea Family)

Foothills, montane.  Meadows, woodland openings.  Spring, summer.
Ryman Creek Trail, June 14, 2011.

Pods are flattened and 7-19 millimeters long.

Stanley Welsh, Astragalus expert (and author of A Utah Flora), indicates that Astragalus tenellus has several key diagnostic characteristics: small, compressed pods; often two flower clusters growing from each leaf joint; and stipules that blacken on drying.  (The stipules are small sheaths that can be seen in the lower right of this photograph.)

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
Eradicated
Questionable presence

Range map for Astragalus multiflorus