Synonym(s): Holcus halepensis, Sorghum miliaceum
Family: Poaceae (Grass Family)
Duration and Habit: Perennial Grass/Grasslike
Perennial with vigorous rhizomes. Coarse grass with reddish to purplish-black panicles, to 2 m tall. Plants can rapidly develop colonies. Johnsongrass is considered one of the 10 most noxious weeds in the world. It is especially troublesome in cotton fields in California.
Ecological Threat: Johnsongrass grows rapidly, is highly competitive with crops, and can be difficult to control. Infestations in crops can reduce harvest yields significantly. Plants are highly variable and many regional biotypes exist. Healthy plants can provide good forage for livestock. However, foliage of johnsongrass and other sorghums can produce toxic amounts of hydrocyanic acid when exposed to frost, stressed by drought, or damaged by trampling or herbicides and may be poisonous to livestock when ingested.
Biology & Spread: Panicles retain seed or shed seed near the parent plant (shatter). Seed disperses to greater distances with wind, water, agricultural activities, and animals. Some seed survives ingestion by birds and mammals. Unlike commercial sorghums, glumes tightly enclose seeds and can protect seeds from decomposition in the soil for several years. Photosynthesis is by the C4 pathway.
History: Brought to South Carolina in the early 1800s as a forage crop. Continues to spread by seed dispersal in agricultural machinery.Introduced from the Mediterranean region.
U.S. Habitat: Disturbed sites, roadsides, fields, agronomic and vegetable crops. Grow best on fertile, well-drained soils in warm temperate to sub-tropical regions where some warm season moisture is available. Also orchards, vineyards, cotton fields, ditchbanks. Often grows in moist soils.
U.S. Nativity: Introduced to U.S.
Native Origin: Africa, Asia (NatureServe Explorer)
U.S. Present: AL, AR, AZ, CA, CO, CT, DE, FL, GA, HI, IA, ID, IL, IN, KS, KY, LA, MA, MD, MI, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, PR, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
List All Observations of Sorghum halepense reported by Citizen Scientists
Fall panicum [Panicum dichotomiflorum Michaux][PANDI] is a summer annual, to 1 m tall, that resembles johnsongrass. Nodes and internodes of fall panicum give the plant a zig-zag appearance. Unlike weedy sorghums, fall panicum has ligules that consist of a fringe of hairs and are not membranous at the base. Fall panicum seedlings are smaller than those of Sorghum and have short hairs on the lower side of the leaf blades.
Texas alternatives include Square-stem spikerush (Eleocharis quadrangulata), Sugarcane plumegrass (Saccharum giganteum), and Powdery thalia (Thalia dealbata).
Plants cannot tolerate repeated, close mowing. Repeated tilling every few weeks in summer or winter can help control infestations in agricultural fields. However, tilling once early in the season encourages rhizome growth and new shoots from rhizome fragments. Crop rotations that include winter crops and crops planted in late summer also help to control infestations. Spring burning encourages re-growth from rhizomes. Some biotypes are resistant to certain herbicides.USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
Miller, J.H. 2003. Nonnative invasive plants of southern forests: a field guide for identification and control. Gen. Tech. Rep. SRS-62. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 pp (USDA SRS).
Encycloweedia, California Department of Food and Agriculture
The Quiet Invasion: A Guide to Invasive Plants of the Galveston Bay Area (www.galvbayinvasives.org). Lisa Gonzalez and Jeff DallaRosa. Houston Advanced Research Center, 2006.
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