Scientific names: Sorghum halepense, previously Holcus halepense
Other names: means-grass, aleppo grass, grass sorghum, Egyptian millet
Johnsongrass (Sorghum halepense) is a perennial grass that aggressively spreads by an abundance of rhizomes, which enables this weed to monopolize an area. It was initially brought into the US as a forage crop; however, it is now one of the most problematic agricultural and horticultural weeds due to its ability to outcompete crops. It is an emerging issue in NYS as a problem in field crops, since it greatly reduces the yield of corn, sorghum, soybean, cotton, and leguminous forages. It can grow in a variety of soil conditions, and grows well in soils with a 5-7.5 pH range.
Flower heads of johnsongrass.
Photo by Barry Fitzgerald of USDA Agricultural Research Service, via Bugwood.org.
Identification
Seedlings the shape of the leaf bud is rolled, the ligule is membranous, the auricle is absent, and the leaf blade in seedlings is hairless. The sheath is also hairless and has a maroon tinge as a seedling.
Seedling leaf size: 0.6-1 inch (1.5-2.5 cm) long by 0.16-0.24 inches (0.4-0.5 cm) wide
True leaf blade size: 1.6-7 inches (4-18 cm) long by 0.1-0.2 inches (0.25-5 cm) wide
Seedling of johnsongrass.
Photo by Ohio State Weed Lab of Ohio State University, via Bugwood.org
Leaves have a prominent white midrib.
Leaf blade size: 8-24 inches (20-61 cm) long by 0.2-2 inches (0.5-5 cm) wide
Sideview close up of ligule and collar region of johnsongrass.
Photo by Ohio State Weed Lab of Ohio State University, via Bugwood.org
White midrib on the leaf blade of johnsongrass.
Photo by Ohio State Weed Lab of Ohio State University, via Bugwood.org
Multiple johnsongrass plants pictured with white midrib shown.
Photo by Karen A. Rawlins of University of Georgia, via Bugwood.org
Rhizomes and root system of johnsongrass.
Photo by Ohio State Weed Lab of Ohio State University, via Bugwood.org
Flowers/fruit: The seed head is a large, open panicle perhaps with a purplish hue. Seeds are dark red to black oval when mature and are oval in shape.
Inflorescence length: 6-20 inches (15-51 cm)
Seed length: 0.1-0.2 inches (3-5 m)
Inflorescence (type: panicle) of johnsongrass.
Photo by Barry Rice of sarracenia.com, via Bugwood.org
Spikelets of johnsongrass.
Photo by Julia Scher of Federal Noxious Weeds Disseminules, USDA APHIS PPQ, via Bugwood.org
Seeds of johnsongrass.
Photo by Julia Scher of Federal Noxious Weeds Disseminules, USDA APHIS PPQ, via Bugwood.org
Similar species
Table 6: Shows johnsongrass (Sorghum halpense) similarities and differences in identification compared to its similar species: shattercane (Sorghum bicolor) and fall panicum (Panicum dichtomiflorum).
| Species | Johnsongrass (Sorghum halepense) | Shattercane (Sorghum bicolor) | Fall panicum (Panicum dichtomiflorum) | ||
|---|---|---|---|---|---|
| Similarities | Smooth to rough leaf blades; sheaths smooth; white midvein | Closely related to Johnsongrass | Similar foliage; white midvein | ||
| Differences | Perennial; thick and vigorous rhizomes; leaf blade (0.08-0.20 in or 2-5 mm) | Annual; doesn't have large rhizomes; wide leaf blades; (0.40-0.80 in or 1-2 cm); seeds are larger and rounded | Annual; much smaller than Johnsongrass; hairy ligule, not membranous at base |
Management
For an optimal control practice an integrated strategy should be applied since johnsongrass is a perennial weed.
Chemical
See Cornell’s Turfgrass and Landscape Weed ID for lists of chemical control options. You can also use CCE Eastern NY Horticulture’s herbicide lookup tool to find the efficacy of various herbicides on johnsongrass seedlings. For general guidance on weed control, get the latest edition of the Cornell Crop and Pest Management Guidelines.
Non-chemical control
Johnsongrass is difficult to control worldwide. Spread prevention is the best method, ensuring rhizomes are not brought in from infested areas on used equipment or in amendments/fill. Once johnsongrass has arrived, best practices focus on exhausting or killing rhizomes paired with curbing seed production and establishment. A key step in determining the best course of action is to determine rhizome depth and target with tillage, which is an effective non-chemical control method. Depending on your environment, overheating the rhizomes (effective in the tropics because of darker soil color) or freezing the rhizomes (effective temperate regions because of snow) are methods of controlling this persistent weed.
Herbicide resistance
Reported as of 2021:
North and Central America
U.S.
Group 1 (5 states)
Group 2 (5 states)
Group 9 (3 states)
Mexico
Group 2
Other continents
Asia
Groups 1 and 2
Australia
Group 9 (Queensland)
Europe
Groups 1 and 2
South America
Groups 2
2-way multiple resistance to groups 1 and 9 (Argentina)
For a more detailed report, please visit the reference section below or visit the International Herbicide-Resistant Weed Database homepage for more information: http://www.weedscience.org/Home.aspx
Resources
For more ID info check out the University of Missouri Weed ID Guide on johnsongrass.
UC IPM also has identification information on johnsongrass.
University of Missouri Extension has management specifics for johnsongrass.
Cornell University’s Turfgrass and Landscape Weed ID app. Identification and control options for weeds common to turf, agriculture, and gardens in New York; uses a very simple decision tree to identify your weed.
Oklahoma State University has a blog post discussing whether johnsongrass is a weed or forage crop. For information on this, check out this post on johnsongrass.
For more information please look for the upcoming book, Manage Weeds on Your Farm: A Guide to Ecological Strategies by Charles L. Mohler, John Teasdale, and Antonio DiTommaso (Publisher: SARE Outreach, expected late fall of 2021).
Uva R H, Neal J C, DiTomaso J M. 1997. Weeds of the Northeast. Book published by Cornell University, Ithaca NY. The go-to for weed ID in the Northeast; look for a new edition sometime in 2019.
Herbicide resistance details
North America
U.S.
Mid-Atlantic: Virginia, group 1 (sethoxydim); West Virginia, group 2 (nicosulfuron)
Mid-West: Indiana, group 2 (nicosulfuron); Kentucky, groups 1 (fluazifop-butyl) and 2 (foramsulfuron, nicosulfuron, and primisulfuron-methyl).
South East: Tennessee, group 1 (fluazifop-butyl and quizalofop-ethyl); Louisiana groups 1 (clethodim, and fluazifop-butyl) and 9 (glyphosate); Mississippi, groups 1 (fenoxaprop-ethyl, fluazifop-butyl, and quizalofop-ethyl), 2 (pendimethalin), and 9 (glyphosate); Arkansas, group 9 (glyphosate)
South West: Texas, group 2 (imazethapyr and nicosulfuron)
Mexico
Group 2 (foramsulfuron, nicosulfuron, primisulfuron-methyl, and rimsulfuron)
Other continents
Asia
Israel, groups 1 (clethodim, fluazifop-butyl, and haloxyfop-methyl) and 2 (rimsulfuron)
Australia
Queensland, group 9 (glyphosate)
Europe
Greece, group 1 (propaquizafop, and quizalofop-ethyl); Hungary, group 2 (foramsulfuron, and nicosulfuron); Italy, groups 1 (fluazifop-butyl, haloxyfop-methyl, propaquizafop, and quizalofop-ethyl) and 2 (nicosulfuron); Serbia, groups 1 (fenoxaprop-ethyl, fluazifop-butyl, haloxyfop-methyl, propaquizafop, and quizalofop-ethyl) and 2 (imazamox, nicosulfuron, propoxycarbazone-Na, pyroxsulam, and rimsulfuron); Spain, group 2 (nicosulfuron)
South America
Argentina, multiple resistance to groups 1 and 9 (glyphosate, and haloxyfop-methyl); Chile, group 2 (nicosulfuron); Venezuela, group 2 (foramsulfuron, iodosulfuron-methyl-Na, and nicosulfuron)
Please visit International Herbicide-Resistant Weed Database for more information on resistance.