Johnsongrass
Sorghum halepense · Warm-season, Perennial, C4
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Forage Grass (with management)
Variety / Cultivar
Common Johnsongrass (no specific cultivar)
Hardiness Zones
USDA Hardiness Zones 6-10; heat-tolerant, goes dormant and turns brown after the first hard frost.
About This Grass
An aggressive, tall, coarse perennial grass that can reach 3 to 10 feet in height. It features light green to medium green foliage with a prominent white midvein. The seed heads are large, open, many-branched panicles that turn purplish-bronze at maturity.
Blade Characteristics
Coarse blade width (10-30mm), flat shape with a pointed tip. Distinctive prominent white midrib. Vernation is rolled in the bud. Ligule is membranous with a fringe of hairs; auricles are absent.
Root System
Deep and extensive fibrous root system combined with thick, fleshy, scaly rhizomes. High thatch tendency and rapid establishment; highly difficult to eradicate once established.
Growing Information
Origin Region
Native to the Mediterranean region; widely naturalized across the United States and global warm climates
Growth Habit
Strongly rhizomatous; aggressive spreading underground stems forming dense colonies
Sunlight & Water Needs
Full sun preferred (minimum 6 hours); high drought tolerance due to rhizomes; adaptable to varied soil types from clay to loam with a pH of 5.5 to 7.5.
Mowing & Maintenance
Not intended for turf; if managed for forage, mow at 4-6 inches. Requires frequent cutting to prevent seed production. Maintenance level: Low (if unmanaged) to High (for eradication).
Special Characteristics
Highly invasive; extreme traffic tolerance; drought recovery via rhizomes; salt-tolerant. Danger: can produce toxic prussic acid (cyanide) for livestock if stressed by frost or drought.
Ecological Information
Introduced/Invasive status in the US; provides limited cover for small wildlife but often displaces native flora; excellent soil stabilizer for erosion but becomes a monoculture weed; companion grasses are typically avoided due to its dominance.