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Johnsongrass (Sorghum halepense)
ODA rating: B
Oregon johngrass distribution
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Images courtesy of Rich Old, XID Services
If images are downloaded and used from the ODA web site please be sure to credit the photographer.
Perennial that grows three to ten feet tall. Leaf blades are flat with a prominent white midvein. The stems are solid with prominent, swollen nodes. Flowers or spikelets, are in pairs at the lower end of the flowering stalk, and in threes at the upper end.  Johnsongrass has fibrous roots and extensive, thick creeping rhizomes.
Johnsongrass is one of the world’s  worst weeds. It is extremely competitive and a serious weed in corn production. Newer herbicides have reduced its impact in many crops but significant efforts are still directed at controlling this plant. Johnsongrass is an alternate host to corn leaf gall, maize dwarf mosaic, wheat streak mosaic, and beet yellows viruses; it also harbors sorghum midge, an insect pest of cultivated sorghum.
Known hazards
It has been reported that livestock grazing on large amounts of young, stressed, or herbicide treated Johnsongrass are at risk of hydrogen cyanide poisoning. 
This species was introduced and planted as a forage species extensively in the United States: Montana, Michigan, South Dakota, Wyoming, Iowa, Nebraska, and California.
Distribution in Oregon
The first reported site in Oregon was 1959 in Morrow County.

Biological controls
No approved biocontrol agent is available.