An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press




TANSYMUSTARD-Descurainia pinnata (Walt.) Britt.

DESCRIPTION-An erect annual or winter annual, 1/2 to 3 feet high, which reproduces only by seeds. The plants are usually ash colored from the many short soft, forked or starlike hairs, or they may be only moderately hairy and green. The stems are often purplish. The alternate leaves are divided once or twice into fine segments, 1 to 4 inches long.

The tiny flowers, about 1/12 inch long, are yellow or whitish, and on short slender spreading stalks, which elongate as the pods mature. They occur along the upper part of the stems. The short narrow seedpods are somewhat stubby, 1/4 to l/2 inch long, and have 2 rows of seeds in each half. The tiny oblong seeds are dull red, about 1/25 inch long, and have a groove on 1 side.

DISTRIBUTION-Tansymustard is a native weed which is abundant in moist spots throughout the state on sandy, rock, or disturbed soil of riverbeds, washes, mesas, canyons, slopes, and swales in creosote desert, grassland, sagebrush, oak, and pinyon-juniper associations. It is also a troublesome weed in cultivated lands, grain fields, city streets, and waste places; 100 to 7,000 feet elevation; flowering December to August, mostly March and April at the lower elevations.

POISONOUS PROPERTIES-Tansymustard contains no known poisonous principles, but may cause trouble under certain conditions. These plants appear on the ranges in abundance in early spring, and livestock may eat them almost exclusively. Animals may be unable to eat or drink, as a result of eating large quantities over a long period of time. The pods are also relished by livestock. The mature seeds are rich in oil of mustard.

FLIXWEED-Descurainia sophia (L.) Wats.

DESCRIPTION-Similar to tansymustard, but with much more finely divided leaves, brighter green and less hairy. The pods are much longer, 3/4 to 1 1/3 inch long, and very narrow; the seeds are in 1 row in each half.

DISTRIBUTION-Introduced from Eurasia, flixweed is found in the same type of places with the same general distribution as tansymustard, but is not as abundant except in some local areas; flowering mostly March to May.

Copyright (c) 1972 The Arizona Board of Regents

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