An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
BROOM SNAKEWEED-Gutierrezia sarothrae (Pursh) Britt. & Rusby
DESCRIPTION-Low compact perennial half-shrub, 1/2 to 1 1/3 (or 2) feet high, from a woody base which becomes a branched crown in old plants, reproducing by seeds only. The innumerable stems are very slender and much-branched, woody only at the base. The slender alternate leaves are very numerous on the stems, mostly 3/8 to 1 1/2 inches long, and 1/25 to 1/12 inch broad, with smooth margins.
The yellow flower heads are very small, covered by sticky resin, distinctly topshaped, broader above and tapering to a narrower base, 1/8 to 1/4 inch long, and about 1/8 inch in diameter. They have 3 to 8 deep yellow short marginal (ray) flowers which roll up in age, and 3 to 8 central (disk) flowers. The flower heads are stalkless, or on very short stalks in small dense clusters at the tips of the many small branchlets. Each flower head produces 6 to 16 achenes. These are narrowly oblong, about 1/25 inch long, hairy, and bear at the large end 8 to 12 narrow white scales, 1/25 inch long.
DISTRIBUTION-A native and serious range pest growing well on a wide range of soil sites from gravelly shallow immature soils to deep, sandy, well-developed loams and clayey soils. Common on rangelands from Apache to Mohave counties; at elevations from 2,800 to 8,000 feet; flowering from July to November. It is an aggressive and obnoxious weed, covering millions of acres in northern Arizona. It increases markedly on open grassland and woodland ranges with continued heavy grazing use by livestock and improper range management. Increase in abundance is generally accompanied by loss in grazing capacity.
THREADLEAF SNAKEWEED-Gutierrezia microcephala (DC.) Gray
DESCRIPTION-Very similar in appearance, habitat, and distribution to broom snakeweed. It differs principally in having fewer flowers in each flower head, and thus the flower heads are noticeably narrower. There are only 4 to 5 marginal flowers. and 1 to 3 central flowers in threadleaf snakeweed.
POISONOUS PROPERTIES OF SNAKEWEED-Usually unpalatable plants, but livestock may eat the snakeweeds under conditions of forage shortage. Sheep, cattle, and goats are poisoned, and although death may occur, the major effect of poisoning is abortion. Cattle are more prone to abortion than are sheep and goats.
Copyright (c) 1972 The Arizona Board of Regents