An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
TUMBLE PIGWEED-Amaranthus albus L.
DESCRIPTION-A bushy branched annual 1/2 to 4 feet high, with light green or whitish stems, which reproduces by seeds. The bright green alternate leaves, 1 to 3 inches long and oblong or spatulashaped, are often reddish purple beneath, with the veins and margins white edged, sometimes with a short bristle at the tip.
The short greenish flowers are in short narrow clusters in the leaf axils; the 3 awlshaped spiny bracts below each flower are much longer. The little papery fruit opens by a circular line, and the top comes off like a lid. The shiny diskshaped seeds are dark reddish brown or black, about 1/25 inch in diameter, with a minutely roughened surface. At maturity the large globeshaped plants are stiff, bristly, and sticky to the touch. They often are broken off at the ground level, and carried about by the wind as a tumbleweed.
DISTRIBUTION-Tumble pigweed is a common weed throughout Arizona, and a pest in cotton, flax, and other cultivated fields. It also grows in river bottoms, roadsides, waste places, and eroded or rocky slopes on rangelands; 100 to 8,000 feet elevation; flowering May to November. This weed was introduced from tropical America.
PROSTRATE PIGWEED-Amaranthus graecizans L.(A. blitoides Wats.)
DESCRIPTION-Prostrate pigweed is very similar to tumbling pigweed. The stems, however, instead of being erect, are prostrate, forming mats on the soil 1/2 to 2 feet long, and are often pink or purplish rather than pale green. The 3 spiny bracts at the base of each flower are only slightly longer than the flowers, and the seeds are shining black.
DISTRIBUTION-Prostrate pigweed occurs throughout the state in cultivated fields. It is also found along roadsides, river bottoms, mesas, washes, alkaline sinks, railroad tracks, and denuded areas in overgrazed ranges in mesquite, oak, or pine forests; 100 to 8,200 feet elevation; flowering May to November.
Copyright (c) 1972 The Arizona Board of Regents