An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
MORNING GLORY FAMILY-Convolvulaceae
DESCRIPTION-A restricted noxious weed in Arizona, dodder is a parasitic, rootless, leafless annual vine with beautiful yellow or orange, stringlike, twining stems, reproducing only by seeds. The leaves are reduced to colorless scales, and the plant has no green matter. Upon germination, the long slender seedling, at first dependent upon food stored in the seed, coils about an available plant to which it becomes attached by numerous suckers. It then depends upon its host for all food; should the seedling fail to reach a host, it soon dies.
The stems branch greatly, forming a network about the host and spread on to the next plant, the growing parts continually producing new suckers. Although branches of the host or the entire host may die, the only part of the vine that dies is that portion directly attached to lifeless material.
The white or cream colored flowers are bellshaped, fleshy mostly 5-lobed, 1/12 to 1/4 inch long, and arranged in clusters along the stems. The globeshaped seedpods are thin and paperish, producing 2 to 4 seeds.
DISTRIBUTION-Dodder is a noxious weed, sometimes parasitizing important crops, particularly alfalfa and clover, with whose seeds it is often mixed. Of the 15 species in Arizona, only 3 are common, ranging from Coconino and Yavapai counties southward; 100 to about 5,000 feet elevation; flowering June to November, but mostly July to September.
FIELD DODDER-Cuscuta campestris Yunck.
DESCRIPTION-The withered flower parts are persistent about the base of the seedpod, and the grayish tan, eggshaped seeds are 1/25 to 1/16 inch long. Growing on many hosts, but particularly on sugar beets also alfalfa, clover, and other legumes.
LARGESEED DODDER, bigseed alfalfa dodder-Cuscuta indecora Choisy
DESCRIPTION-The withered flower parts completely cover the seedpods; the reddish tan, circular seeds are 1/16 to 1/12 inch at the longest axis. Attacks woody as well as herbaceous plants, often on sunflower, goldenrod, aster, and burrobrush; frequently on legumes such as alfalfa, mesquite, and catclaw.
UMBRELLA DODDER-Cuscuta umbellata H.B.K.
DESCRIPTION-The flowers are in umbrellalike clusters, with the withered flower parts wholly covering the seedpods. The greenish to reddish tan seeds are 1/25 to 1/16 inch long. Especially common on puncturevine, often covering large areas, also on cultivated beets, horse purslane, and various spiderlings and spurges.
Copyright (c) 1972 The Arizona Board of Regents