Fabaceae / Astragalus spp. / Locoweed / Milk-Vetch

Any plant with the common name “Locoweed” is either one you want to stay far away from…or use to attain transcendence into some ethereal higher realm. Astragalus are a genus of dichotomy, while perhaps most well-known for their toxicity, especially to livestock; they have a long history of ethnobotanical use and certain species remain both culturally and commercially important to humans.

The genus name was used by Dioscorides and is derived from the classical Greek word astragalos, meaning “anklebone” (Huxley and Griffiths 1992; Quattrocchi 2000). This bone was used in ancient times as a form of dice. One conjecture is that the name was applied because the rattle of the seeds in the dry legumes may have resembled the sound of dice in a thrower (Barneby 1964).

Physiology can present in a multitude of forms. Plants can be both annual or perennial. Leaves typically 1-pinnately compound (rarely palmate), with leaflets numbering from 1-20 with a terminal. Inflorescences elongate or capitate racemes borne at ends of peduncles arising in axils of leaves. Flowers are bilateral; keel petals with small protrusion at base locking into pit on adjacent wing. Colors range from They have 10 stamens, 9 free and 1 fused. Ovaries and fruits are generally sessile, with the fruits being 1-2 loculed and dehiscent. (Jepson eFlora 2025, Burrows 2013). They are often difficult to identify, with fruits and flowers almost always needed to differentiate.

This genus has perhaps the most world-wide diversity of any vascular plant with over 2,900 distinct species! California alone hovers near the 100 species mark and within 30 miles of our home in the Sierra Nevada, we can find nearly 20. As you may imagine, Astragalus can occur in a large range of habitat types, though they tend to prefer arid or semi-arid landscapes. Lucky for us the toxic species in North America are almost entirely found in the west (Burrows 2013)…go us…

So on that note...There are two primary phytochemical groups which can give some species of Astragalus their unfortunate action. The first is an alkaloid Swainsonine. This is the chemical compound primarily thought to be responsible for it's namesake "locoism" and can cause neurological ailments in behavior (including violence), coordination, difficulty eating, cardiac failure at higher elevations, reproductive deformities, abortions, and impaired fertility of both sexes. The second is caused by nitro-toxins and leads to Cracker-Heels, so named because inflicted animals often strike their hooves together, a symptom of underlying muscle and nerve damage (Cook 2009).

While research on this expansive genus is still arguably in it’s infancy, there is ample ethnobotanical documentation of these plants being used in everything from ceremony to treatment of ringworm! Along those lines, many medicinal uses are in regards to cleansing the body. The dried roots of A. membranaceus or A. mongholicus (Huangqi) are used widely in TCM. Commercially, the most valuable part of Astragalus taxa is the gum tragacanth, used in a variety of products (and in Ayruveda to treat respiratory, digestive and metabolic disorders), primarily sourced from A. gummifer. This is obtained by first causing damage to the plant’s bark or roots, then collecting the hardened, dried sap which exudes.