An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
BUR CLOVER-Medicago hispida Baertn.M
DESCRIPTION-A bright green nearly hairless annual, or sometimes winter annual, reproducing only by seeds. The weak stems branch from the base, and spread or lie on the ground with the tips ascending, 1/4 to 2 feet long. The leaves are alternate, and divided into 3 leaflets which arise from a common point at the end of the leaf stalk. The leaflets are somewhat wedgeshaped, with toothed edges and indented tip. There is a pair of small leaflike structures (stipules) with long irregular teeth where the leaf stalk joins the stem.
The small yellow pealike flowers are borne 3 to 5 in a cluster near the end of short stalks. The peculiar pods are net-veined, spirally coiled, about 1/4 to 1/3 inch in diameter, and are indehiscent. The spiral consists of 2 or 3 turns, with a double row of curved prickles along its sharp edge.
The pods are straw colored or brown when mature, and contain several kidney-shaped seeds. The seeds are yellowish or tan colored, about l/8 inch long, and slightly sticky.
DISTRIBUTION-Bur clover is an Old World introduction. Although it is high in forage value, it is a very troublesome weed in Bermuda lawns, and to some extend in alfalfa seed crops in southern and central Arizona; 100 to 5,500 feet elevation; flowering mostly March to May, but in moist situations it may flower at almost all seasons.
ALFALFA-Medicago sativa L.
DESCRIPTION-One of the most important of all cultivated forage plants, alfalfa, also an Old World introduction, is very closely related to bur clover and black medic. It is entirely different in appearance, since it is an erect perennial with blue or violet flowers, but its seeds are similar.
Copyright (c) 1972 The Arizona Board of Regents