Johnson Grass
Sorghum halepense · Warm-season, Perennial, C4 grass
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Forage/Pasture (with limitations)
Variety / Cultivar
Wild type (No specific commercial cultivar, as it is largely considered a noxious weed)
Hardiness Zones
USDA Zones 6-11; very heat tolerant; foliage dies back after first frost and enters dormancy, but rhizomes survive winter underground.
About This Grass
An aggressive, tall-growing perennial grass reaching heights of 3 to 8 feet. It has a coarse texture, bright green color, and produces large, open, pyramidal panicle seed heads that turn reddish-brown or purple at maturity.
Blade Characteristics
Coarse, flat blades 10-20mm wide with a prominent, white midrib. Tips are pointed; vernation is rolled. Ligule is large, membranous and fringed with hair; auricles are absent.
Root System
Deep, extensive fibrous roots combined with thick, creeping rhizomes. High establishment speed and high thatch tendency; extremely difficult to eradicate once established.
Growing Information
Origin Region
Native to the Mediterranean region; naturalized globally across temperate and tropical zones including the United States, particularly the South and Midwest.
Growth Habit
Rhizomatous (aggressive, scaly, fleshy underground stems) and bunch-type; forms dense colonies and mats.
Sunlight & Water Needs
Full Sun (minimum 6-8 hours); high drought tolerance due to rhizomes; adaptable to varied soils but prefers fertile, well-drained bottomlands; pH 5.5 to 7.5.
Mowing & Maintenance
Not typically mowed as turf. For control, frequent close mowing to deplete rhizomes is required. Low maintenance requirement for growth; resists most management efforts.
Special Characteristics
Extremely high wear tolerance; salt tolerant; highly invasive; can produce toxic hydrocyanic acid (cyanide) and nitrates if stressed by frost or drought, making it dangerous for livestock.
Ecological Information
Introduced and widely considered a noxious weed in numerous states. High soil stabilization but displaces native vegetation. Provides some cover for small wildlife but is ecologically damaging.