An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press




DALLISGRASS-Paspalum dilatatum Poir.

DESCRIPTION-Dallisgrass is a tall perennial from a hard, knotty base, 1 1/2 to 5 feet high, which reproduces only by seed. It has flat leaf blades about 2 to 6 inches long. The flowering part consists of 3 to 5 very narrow branches 1 to 3 inches long, alternate along the upper part of the stem. These bear the spikelets on one side only.

The small pointed spikelets, about 1/8 inch long, are stalkless, and lie in even rows close to the branch. The dark purple stigmas are often conspicuous. The smooth shiny grain is yellowish, nearly circular, and slightly less than 1/8 inch long.

DISTRIBUTION-Dallisgrass is a South American species that grows in the moist or marshy soils of grazing pastures, not on the rangelands. As a weed it is trouble-some in lawns, but also occurs in alfalfa and other crops in southern Arizona-particularly in Pinal, Maricopa, and Pima counties. This grass is planted as a permanent pasture grass in southern Arizona, and has been grown in Apache County, but less successfully. It flowers from April to November.

POISONOUS PROPERTIES-Although dallisgrass is good forage, it is very susceptible to the fungus attacks of paspalum ergot (Claviceps paspali Stevens & Hall). The fungus produces a dark sticky substance similar to axle grease, known as "honey dew," which covers the grass flowers. Paspalum ergot is the chief cause of ergot poisoning reported in Arizona, principally of cattle running in pastures containing dallisgrass.

Copyright (c) 1972 The Arizona Board of Regents

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