Southwest Colorado Wildflowers, Astragalus 2

The Astragalus genus is large and complex. In Colorado Flora, Western Slope William Weber lists over five dozen species with many sub-species. The new Flora of the Four Corners lists fifty-eight species and several dozen varieties of Astragalus in the Four Corners drainage of the San Juan River. In Intermountain Flora Arthur Cronquist lists 156 species and 122 varieties. World-wide there are about 1600 species.

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.

Astragalus lonchocarpus
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, shrublands, openings. Spring.
Canyons of the Ancients National Monument, April 19, 2007.

Clusters of pale yellow-to-cream flowers dangle from several feet of new spring growth. Astragalus lonchocarpus is eye-catching because of its mass of bright green foliage and numerous stems of numerous flowers. Last year's dead flower stalks can be seen at the base of the plants. Leaves are slender and sparse.

Notice that the flower stems on the left of the plant have all been snipped off by browsing deer.

"Lonchocarpus" is Greek for "spear-shaped fruit", or "long pod".

Augustus Fendler collected the first specimen of this plant in 1847 near Santa Fe and John Torrey named and described it in 1849.

Astragalus lonchocarpus

Astragalus lonchocarpus
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, shrublands, openings. Spring.
Canyons of the Ancients National Monument, April 19, 2007 and Ojito Wilderness, New Mexico, June 2, 2010.

Astragalus lonchocarpus The flower banner petal is gracefully curved backward at about a 45 degree angle from the very long wing petals. The banner is curved inward from both sides and has a blunt tip. The keel petal, the tiny greenish/yellow nub clasped by the two wings, is considerably shorter than the wings.

Astragalus lonchocarpus

Astragalus lonchocarpus
Fabaceae (Pea Family)

Semi-desert, foothills. Woodlands, shrublands, openings. Spring.
Lone Mesa State Park, May 25, 2009.

Leaves are long, narrow, and widely spaced and stems are numerous, thick, and vibrant green.

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 lonchocarpus