Johnsongrass (Sorghum Halpense) is a Mediterranean native plant brought to the United States 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 (creeping underground stems). Johnsongrass is the sixth most serious weed in the world. When under moisture stress or after frosts, Johnsongrass can produce toxic levels of hydrocyanic acid. At certain times, under certain conditions during the growing season, Johnsongrass can be toxic to horses and other livestock.

Johnsongrass infestation can be a concern and serious problem for landowners. Individuals with knowledge and an understanding of Johnsongrass often think of this as a problem associated with farmland but, Johnsongrass can be in homeowners’ flower beds and vegetable and herb gardens as well. Johnsongrass can also be found spreading along the shoulders and medians of roads and highways.

Johnsongrass, if allowed to establish itself, is a noxious weed that will choke out all other native grasses and crops. It requires extensive and very costly eradication measures. At certain times and under certain conditions during the growing season, Johnsongrass can be toxic to horses and other livestock.

Facts about Johnsongrass:

Toxicity Rating: Moderate to High

Animals Affected: All types, especially ruminants (animals that chew cud)

Dangerous Parts of the Plant: Leaves and stems, especially young plants.

Plant Description: Visit the Virginia Tech Weed ID page for detailed images and information.