An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
BURROWEED-Haplopappus tenuisectus (Greene) Blake
DESCRIPTION-Low spreading perennial half-shrub forming rounded bushes, usually the diameter slightly exceeds the height, l 1/2 to 3 1/3 feet across, and 1/2 to 2 1/2 (or sometimes 3 1/3) feet high; reproducing only by seeds. The many-branched stems are woody below. The older and larger ones have gray bark, while the younger ones usually are yellowish-tan. The young stems, leaves, twigs, and flower heads are sticky from resin. The leaves are alternate, 2/3 to 2 inches long, and are divided into 3 to 5 pairs (often obscurely paired) of slender pointed divisions, 1/25 inch broad and 1/25 to 3/4 inch long. The yellow flower heads are about 1/4 inch long and 1/8 inch broad, but spread when the seeds are mature. They produce only central flowers; the ray flowers, or "petals," are lacking. The flower heads, stalkless or very short-stalked, occur in clusters at the tips of all stems and branches. The achenes are very narrowly topshaped, 1/8 inch long, 4-ribbed or angled, and hairy between the ribs. Arising from the broad end is a tuft of tawny hairs 1/4 inch long.
DISTRIBUTION-Burroweed is a native perennial growing on dry, gravelly to sandy soils on roadsides, waste places, alluvial plains, mesas, and slopes. It is a serious range pest on the desert and desert grassland range of eastern Arizona south of the Gila River in Greenlee, Graham, Cochise, Santa Cruz, Pima. Gila, Pinal, and Maricopa counties; 2,000 to 4,500 feet elevation; flowering August to October. Burroweed, worthless as forage, occupies extensive range areas in southern Arizona; this condition is probably the result of too heavy grazing, drought, protection from fire, or a combination of these factors. Reduction in grazing capacity is serious, and always takes place as the plant invades or increases in abundance.
POISONOUS PROPERTIES-Burroweed ordinarily is not eaten by livestock, but animals may be forced to do so in times of forage shortage. Sheep, cattle, and horses are poisoned due to trementol, an alcohol. The most characteristic symptom is trembling, which may shake the whole body. Suckling animals may be poisoned by their mother's milk. Humans may develop milksickness by drinking milk from poisoned cows.
Copyright (c) 1972 The Arizona Board of Regents