An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press




BITTER RUBBERWEED-Hymenoxys odorata DC.

DESCRIPTION-Low, bushy annual with several or numerous stems, greatly branched and often widely spreading, 1/3 to 2 feet high, reproducing by seeds only. The plant, like pingue, is bitter tasting, and has a pungent odor when crushed.

The leaves are fleshy and divided into 3 to 13 threadlike divisions, 1/16 inch or less broad, the surface gland dotted. A quickly-withering rosette of leaves, 1 to 4 inches long, is formed at the base of the plant. Those on the stem are alternate and 3/4 to 2 1/4 inches long.

The numerous yellow flower heads are 1/3 to 1 inch across, including the golden yellow, 8 to 13 marginal or ray flowers, and the 50 to 75 tiny disk, or central flowers. The heads are borne singly on stalks 1 to 6 inches long at the tips of all the branches, and a single plant may have hundreds of heads. Each flowering head produces 50 or more achenes. These are narrowly topshaped, 1/16 to 1/12 inch long. indistinctly 4-angled, and covered with silvery silky hairs. They bear 5 or 6 whitish pointed scales at the top.

DISTRIBUTION-Bitter rubberweed is a native annual range weed of southwestern United States, growing in moist heavy clay, alkali, adobe, sandy, or alluvial soils. It is most common in drainage areas, as flood plains, lake beds, roadsides, and especially abundant along the bottom lands of the lower Gila River (Yuma County), and Little Colorado River (Navajo and Coconino counties). Found in southern and north central Arizona; 350 to 6,000 feet elevation; flowering January to June. but in moist spots may flower until frost. The plant increases in abundance whenever the grass cover has been thinned by continued too heavy grazing use or by drought.

POISONOUS PROPERTIES-Bitter rubberweed is ordinarily eaten only when good forage is scant. Since it becomes green early in the spring before other vegetation, animals hungry for green feed may be attracted to it. Mature plants and those growing in dry situations are usually more poisonous than young vigorous plants. Although reported to be poisonous to cattle, it is most troublesome to sheep.

Copyright (c) 1972 The Arizona Board of Regents

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