Sorghum halepense
Johnson grass (Sorghum halepense) is a coarse, perennial grass with stout rhizomes that reach 7 feet tall. It grows in dense clumps or nearly solid stands. Johnson grass was introduced into the United States as a forage crop, but became problematic not only to natural communities but also to agriculture. It invades riverbank communities and disturbed sites, particularly fallow fields and wooded edges, as well as native grasslands, where it crowds out native species. Johnson grass is on the Missouri Noxious Weed List.
Johnson grass has a prominent white leaf mid-vein, a rounded stem base, and is virtually hairless. (Eastern gama grass [Tripsacum dactyloides], a native grass found on prairies and sometimes along roadsides, also has a white leaf mid-vein, but its stem bases are flattened). Also, eastern gama grass flowerheads are spikelike whereas those of Johnson grass are in a large, loosely branched panicles as shown above. Consult this Johnson grass vs native look-alikes document for more ID tips.
Dense patches can be controlled by spraying the foliage with 2% glyphosate (Roundup). Best results are obtained when glyphosate is applied to plants that are 18 inches tall to early flowering stage. Alternately, sulfosulfuon (Outrider), at a rate of 1 oz per 100 gallons of water, can be applied via foliar spray before flower stalks set seed. Consult this Missouri Department of Conservation Johnson Grass page for more information.
Identification and fact sheets
- Learn about Johnson grass at Invasive.org
- Johnson Grass vs. Native Look-Alikes: ID guide published 2015 by Susan Farrington, Missouri Department of Natural Resources.
- Read more from the Missouri Department of Conservation about identification, threats, and control practices of Johnson grass
- Invasive plant resources from Missouri Prairie Journal:
Representative photos of Johnson grass:
Johnson grass impact, abundance, and trend in Missouri
