An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
BLUEWEED, yerba parda
BLUEWEED-Helianthus ciliaris DC.
DESCRIPTION-A prohibited noxious weed in Arizona, blueweed is a low bluish or grayish green perennial, 1 to 2 feet high; reproducing by seed, but principally by the widespreading underground system of upright roots and rhizomes. The leaves, which give the plant its characteristic color, are stemless, and may be alternate or opposite. They are narrow to broadly lanceshaped, 1 to 4 inches long, and vary greatly in width, from 1/12 to 3/4 inch. The margins are often very wavy, and bear short stiff hairs. Similar hairs may also occur along the veins on the lower surface; otherwise, the plant is hairless. The flower heads, 1/2 to 1 inch broad, have yellow ray or marginal flowers. The central (disk) flowers are dark purplish brown. The achenes are grayish brown, 4-angled, somewhat wedgeshaped, and about 1/8 inch long, often with dark brown spots at maturity.
DISTRIBUTION-Blueweed is one of the few noxious weeds in the state that is native. It grows in dense colonies in heavy saline or alkaline soil, in sandy loam ditchbanks, in low drainage areas, dry lakes, and roadsides from whence it spreads to cultivated lands. It is found nearly throughout the state from 100 to 7,000 feet elevation, and flowers from May to October. It is especially troublesome in southern Apache and Navajo counties in the White Mountains area, and in the farm areas of Graham, Cochise, Pinal, and Pima counties.
Blueweed is a potential pest in any cultivated field it invades. Cultivation may aid its spread. The rhizomes are cut into pieces and distributed throughout the soil. These pieces are capable of starting new plants. Its growth is so persistent that many crops cannot compete favorably, and eventually may be crowded out. A circular patch of blueweed, 500 feet in diameter, was observed in a bean field near Vernon (Apache County).
Copyright (c) 1972 The Arizona Board of Regents