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Johnsongrass Poaceae
(=Gramineae), the grass family
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Background
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 Johnsongrass is a Mediterranean species brought to the U.S.
as a hay and pasture grass. It spreads by seed in the north, but in central
and southern U.S. it also spreads by rhizomes. Johnsongrass can produce
toxic levels of hydrocyanic acid when under moisture stress or after frosts.
Johnsongrass is the sixth most serious weed in the world.
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Description
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 Johnsongrass is a perennial species over most of its
range, but because it normally winter kills in Idaho, it usually acts as an
annual here. Leaves are grasslike up to 1 inch wide, with a prominent
whitish midvein. The ligule is short and
membranous with a hairy fringe;
auricles are lacking. Stems can grow up to 8 feet in height, but our normal
annual specimens will be closer to 3 or 4 feet tall. Large, open
panicles
are up to 1 foot long and emerge in midsummer.
Spikelets are reddish in
color and most are topped by bent awns. Scaly, finger-thick
rhizomes are
produced from the crown.
DISTRIBUTION:
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Distribution
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 Johnsongrass is found throughout the southern
two-thirds of the 48 states and some counties in Idaho.
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Control
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No biological control agents are available for Johnsongrass,
but herbicides are available that control this weed. |
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© 1999 University of Idaho:
Text and photographs for these pages from Idaho's Noxious Weeds, by
Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita
and Larry W. Lass).
Please contact: Ag Publishing, University of Idaho, Moscow,
Idaho 83844-2240; 208 882-7982 visit the Resources for Idaho website at
http://info.ag.uidaho.edu, for more information about this or other
publications.
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