The University of Arizona Press/Arizona Weeds/Fly Mushroom

An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press

HOARY CRESS,whitetop

MUSTARD FAMILY-Cruciferae

HOARY CRESS-Cardaria draba (L.) Desv. (Lepidium draba L.)

DESCRIPTION-A prohibited noxious weed in Arizona, hoary cress is a grayish green, minutely hairy perennial, 1/2 to 2 feet high, which reproduces by seed, but mostly by thick deeply penetrating vertical and wide spreading, creeping branch roots. The stems are erect and greatly branched in the flowering part. The broadly elliptical leaves, 1 to 31/2 inches long, have toothed to nearly smooth margins. Only the lower leaves are stalked; the others are stalkless and clasp the stem with 2 earlike lobes.

The short flowering branches bear many very small flowers, each with 4 petals about l/8 inch long, giving the plant a flattop appearance. The flowers and the small seedpods are borne on slender spreading stalks about 1/4 to l/2 inch long. The mature seedpods are either heartshaped and broadest at base, or broader above and rounded to obtuse at the base. They are nearly hairless, 1/8 to 1/4 inch broad, and tipped by a slender persistent beak. A central partition separates the 2 halves, each producing 1 (rarely 2) red-brown seed about 1/16 inch long, and about 1/16 inch broad.

DISTRIBUTION-Hoary cress, introduced from Europe and Western Asia, forms large patches in cultivated fields, gardens, pastures, and roadsides. Locally common on ranches in the Springerville-Eager area (Apache County) to Peeples Valley (Yavapai County), northward to Fredonia (Coconino County), and occasionally elsewhere in Arizona; 3,500 to 7,000 feet elevation; flowering April to July. Not widespread enough yet in Arizona to be a major problem, but it should be eradicated where found to prevent its spreading.

HAIRY WHITETOP, hairy-podded whitetop-Cardaria pubescens (C. A. Mey.) Roll. var. elongata Roll. (Hymenophysa pubescens auth.)

DESCRIPTION-Unknown to date in Arizona, but is placed on the prohibited noxious-weed seed list to prevent its entry through commercial seed. Often difficult to distinguish from hoary cress, but differing in its closely hairy seedpods, which are slightly smaller and nearly globeshaped.