Common names: MILKVETCH, LOCOWEED, RATTLEWEED, WOOLLY-LOCO Arizona and California deserts: (Astragalus nuttalianus). White-purple. February-May. Texas deserts: (Astragalus mollissimus). Purple. April-May. Pea family. Size: 4 to 12 inches high.
A very large genus of plants, with 78 species recorded in Arizona alone, Astragalus ranges from the driest, hottest parts of the desert to high mountain peaks and the far north. A. nuttalianus is the commonest of the desert species and is found on dry plains, mesas, and slopes below 4,000 feet from Arkansas and Texas westward to California and south into Mexico.
Some of the species, of which Mollisimus (Wooly-loco) is one, contain a poisonous constituent causing the well-known and often fatal loco disease of livestock, particularly horses. (Loco is a Spanish word meaning “crazy.”) Other species which prefer soils rich in selenium take up enough of that toxic mineral to make them poisonous to livestock, especially sheep.
Nearly all of the species are colorful and spectacular when in blossom, and some of them have a rank, disagreeable odor.
PURPLE
Solanum elaeagnifolium
S. rostratum
Common names: PURPLE NIGHTSHADE, GROUNDCHERRY, WILD POTATO, (TROMPILLO), HORSENETTLE Arizona and California deserts: (Solanum xanti). Purple. April-August. Texas desert: (Solanum elaeagnifolium). Purple-violet. May-September. Potato family. Size: Up to 3 feet.
Quite showy when in flower, these common roadside plants attract considerable attention during the late spring and summer. Some species become troublesome in cultivated fields and are difficult to eradicate. An alkaloid, solanin, reported as present in the leaves and unripe fruits of several species, renders them poisonous. Pima Indians add the crushed berries of S. elaeagnofolium to milk in making cheese.
The yellow-flowered S. rostratum is heavily covered with spines, including both stems and fruit, giving it the name of Buffalobur. This species is said to be the original host of the now widespread pest, the Colorado Potato Beetle.