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Johnsongrass

Johnsongrass
(Sorghum halepense)

A warm season perennial grass with dense rhizomes, listed as invasive in numerous states and countries.

Overview

Regulated areas of Johnsongrass
This species is Prohibited (Red counties)

Other names for this plant include:

  • Scientific names: Andropogon controversus Steud; A. halepensis (L.) Brot.; A. halepensis var. anatherus Piper; A. miliaceus Roxb.; A. miliformis Schult.; Holcus exiguus Forssk.; H. halepensis L.; H. halepensis var. miliformis (Schult.) Hitchc.; H. sorghum var. exiguus (Forssk.) Hitchc.; Sorghum controversum (Steud.) Snowden; S. miliaceum (Roxb.) Snowden; S. miliaceum var. parvispicula Snowden

Ecological threat:

  • This species is considered one of the ten worst invasive weeds in the world. Fifty-three countries, ranging in latitude from 55 N to 45 S report johnsongrass as invasive.
  • Invades wetlands, floodplains, irrigation ditches, undisturbed grasslands, prairies, savannas, and riparian zones.
  • A prolific self-seeder, johnsongrass also spreads via an extensive rhizome system
  • Plant breeders, seed dealers and growers often observe off-type plants or "rogues" of hybrid grain sorghum. Common rogues are the tall outcrosses to sudangrass, johnsongrass or other sorghum types. Sorghum outcrosses with johnsongrass as the male parent often have rhizomes resembling those of johnsongrass. Johnsongrass-grain sorghum hybrids can become a significant weed threat.
  • Contains a toxic cyanide-containing substance which can poison cattle and other livestock.

Classification in Wisconsin: Prohibited

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for johnsongrass was based upon this literature review developed by the department.

Identification

Leaves & Stems: Leaves and stems (culms) are coarse. Plants can reach up to 12 feet tall when flowering.

Flowers, Fruits & Seeds: Open panicle inflorescence ranges from 4-24 inches. Spikelets occur in pairs, with up to 350 per panicle. Lemmas are ciliate usually without awns, but sometimes very short and twisted in some forms.

Roots: Rhizomatous, sometimes forming tuber-like organs. Forms dense tangled root systems in the upper soil surface, extending deeper in loose rich soils.

Distribution

Sorghum_halepense
Counties in WI where Johnsongrass has been reported (as of April 2013). Both vouchered and unvouchered reports included.

Do you have johnsongrass in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical:

  • Small patches can be hand-pulled. Be sure to remove the entire root system and dispose of plant debris properly.
  • For heavier infestations, mowing, tilling and burning may be effective.

Chemical:

  • Glyphosate can be used; herbicide treatment may need to be repeated for several years to ensure effective control.

Photos

View johnsongrass pictures in our photo gallery!

Resources

Sources for content:

  • Johnson, B. et al. 1997. Johnsongrass control. University of Missouri Extension. Accessed 11-22-2010. http://extension.missouri.edu/publications/DisplayPub.aspx?P=G4872
  • Wisconsin State Herbarium. 2010. WISFLORA: Wisconsin Vascular Plant Species. Department of Botany, University of Wisconsin-Madison, WI 53706.
  • Howard, Janet L. 2004. Sorghum halepense. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Links for More Information

Last revised: Monday December 11 2017