This very large genus of plants ranges from the hottest parts of the desert to high mountain peaks and far to the North. More than a dozen species are found in the Zion Region.
Some of the species contain a poisonous constituent causing, the often fatal, loco disease of livestock, particularly in horses.
Loco is a Spanish word meaning “Crazy.” Other species known as Poisonvetch, prefer soils rich in selenium, and take up enough of that toxic mineral to make them poisonous to livestock, especially sheep. The harmless species are called Milkvetch.
Nearly all the species are colorful and spectacular when in blossom, but some of them have a rank, disagreeable odor.
Loco
44. POISONVETCHPea Family
Astragalus sabulonum
This showy species of Astragalus is locally called Rattleweed because, when it is in fruit, its large, bladder-like, thin-walled pods become very brittle and give a distinct rattling sound when shaken. The pods are about one and a half inches long and heavily mottled reddish-brown in color.
The genus of Astragalus has been divided into three groups: Loco, Milkvetch and Poisonvetch. The species poisonous to livestock are commonly called Loco Weeds.
