An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
BROADLEAF MILKWEED-Asclepias latifolia (Torr.) Raf.
DESCRIPTION-A robust, very leafy perennial with milky juice, which reproduces by seeds and by horizontal roots. There is 1 stout, erect stem, often hollow, unbranched or few branched, 1 1/2 to 3 1/2 feet high. There are 5 or more pairs of large thick oval leaves, conspicuously veined, almost stalkless, often as broad as long, and rarely more than 1 1/2 times as long as broad, the tip broadly rounded and often indented.
The fragrant, yellowish flowers, on slender stalks, form drooping umbrellalike clusters at the tops of the branches, and in the leaf axils. These unusual flowers have 5 hoodlike structures with horned crests above 5 reflexed petals. Two to several smooth, brown, woody seedpods are produced on stalks that curve downward. They are about 3 inches long, 1 1/4 inches broad when mature, and contain many flattened seeds. These are distinctly margined, reddish brown, about 1/3 inch long, and 1/4 inch broad. Each seed has a tuft of fine silky white hairs at the narrow end, and is about 1 inch long.
DISTRIBUTION-Broadleaf milkweed is a native plant growing in dry soil on mesas, plains, washes, and often abundant along trails and roadsides in the northern desert and short grassland ranges of northeastern and central Arizona. Found from Apache to Coconino and Yavapai counties; 3,000 to 7,000 feet elevation flowering from June to August, fruiting until October. This plant tends to increase in heavily grazed areas.
POISONOUS PROPERTIES-The green plants before and during the flowering stage are poisonous to sheep, cattle, and goats. Poisoning has occurred early in the spring before the grass had started to grow. Approximately 1% of animal's weight of green plant causes death, while only 0.2% of western whorled milkweed is required.
Copyright (c) 1972 The Arizona Board of Regents