An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
CAMPHORWEED-Heterotheca subaxillaris (Lam.) Britt. & Rusby
DESCRIPTION-Tall coarse hairy annual or sometimes biennial, with a strong odor, from a taproot; reproducing by seeds only. There is a single principal stem, mostly branching only at the top and spreading, resembling a telegraph pole, 2 to 6 feet high. It is more or less covered by long, spreading hairs with the upper branchlets and flower stalks bearing gland-tipped hairs filled with a sticky secretion.
The leaves are alternate with toothed margins. The lower and basal leaves are large, oval, or oblong; they are on a slender stalk, and usually there is a pair of leaflike lobes on either side of the stalk base. The upper leaves are much smaller and stalkless, their bases heartshaped and clasping the stem.
The flower heads are yellow, about 1/4 to 3/8 inch high, and 1/2 to 3/4 inch in diameter, including the 20 or more deep yellow petallike ray or marginal flowers. The 35 or more central (disk ) flowers are also yellow. The achenes are of 2 kinds, both of which are maroon colored and 1/12 to 1/8 inch long. The ray achenes are 3-angled, entirely hairless and without the apical tuft of hairs. The achenes of the central flowers are covered by whitish hairs, not 3-angled, and have a tuft of brownish hairs at the larger end.
DISTRIBUTION-Camphorweed, a native of tropical America, grows in moist or dry sandy soil along ditchbanks in cultivated fields, or edges, roadsides, and low places where water collects, also in sandy washes. Although it grows in dry soil, it attains its best growth in moist soil, as in and around the irrigated lands. Common throughout central and southern Arizona, 100 to 5,500 feet elevation; flowering March to November, but largely in late summer.
Copyright (c) 1972 The Arizona Board of Regents