An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press

RUSSIAN THISTLE, tumbleweed

Illustration

GOOSEFOOT FAMILY-Chenopodiaceae

RUSSIAN THISTLE-Salsola kali L. var. tenuifolia Tausch.

DESCRIPTION-A restricted noxious weed in Arizona, Russian thistle is an intricately branched, bushy globular annual, 1/2 to 6 feet high, with ridged and often reddish stems, reproducing only by seed. At maturity, the hard, prickly plant breaks at the ground level, becoming a "tumbleweed." The grasslike seedlings and the young plants are fleshy and tender, with alternate, narrow pointed leaves, 1/2 to 2 inches long. These leaves drop off; the short, stiff mature leaves are awlshaped, and end in a spine.

The tiny whitish flowers are clustered at the base of the leaves along the upper branches. There are no petals, but the 5 dry flower parts enlarge, and each develops a large veiny wing. These meet to form a cover over the topshaped, reddish, slightly winged fruit. Each fruit has 1 gray to brownish yellow seed, with the coiled embryo visible.

DISTRIBUTION-Russian thistle is one of the most prolific and obnoxious weeds throughout the state. Abundant in southern Arizona in irrigated areas, waste grounds, and river bottoms; also common in small grains. In northeastern Arizona, it is very common on overgrazed ranges and pastures in grasslands, chaparral, pinyon-juniper, and frequently in yellow pine; 150 to 7,000 feet elevation; flowering May to October or November.

A native of Russia, this plant was brought into the United States in flax seed about 100 years ago, and has spread very rapidly. It is a prolific seeder: one plant may produce thousands of seeds. The seeds remain viable for years, and are scattered as the plant rolls along. It is a host plant for the sugarbeet leafhopper, which carries the virus causing curly top in beets. It is also the source of "blight" in other crop plants such as tomatoes, spinach, and beans.

POISONOUS PROPERTIES-May store toxic amounts of nitrates after periods of fast growth.

Copyright (c) 1972 The Arizona Board of Regents



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