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Arizona
Range Grasses Back to the Table of Contents
Growth habit: A large aggressive sod grass, 3 to
6 feet tall, growing from a scaly, underground rootstock.
Occurrence Throughout the state below 5,000 feet where moisture is
adequate for its growth. This grass is particularly abundant along irrigation
canals and along the edges of fields and roadsides. It often becomes
an undesirable weed in cultivated fields. Forage Value Johnson grass makes good forage for grazing animals but
is particularly valuable for cattle and horses. It is a productive hay
plant. As the plants are coarse, the best quality hay is obtained when
the plants are cut in the boot stage of growth. When growth is stopped prematurely by drought or frost, prussic acid accumulates in the stems and leaves. This forage may then be highly toxic to grazing livestock. When cut for hay, the acid remains in the hay and the toxic effects are as severe as when the standing grass is grazed.
Management of Johnson grass is largely a matter of preventing
poisoning. The grass is hardy, resistant to grazing, and is killed only
by extreme drought. Only a few animals should be turned in when a Johnson grass field is first opened to grazing. These animals should be watched closely for the first twenty-four hours and removed at the first indication of trouble. If no poisoning is observed during this period the forage may be assumed to be safe. Livestock on Johnson grass should always be closely watched, particularly during periods of sudden weather changes. The most hazardous times are in the spring and fall when frosts are likely to occur, and during summer drought.
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Cooperative
Extension,College of Agriculture & Life Sciences, The University of
Arizona