Johnson Grass
Sorghum halepense · Warm-season, Perennial, C4 grass
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Pasture/Forage Grass
Variety / Cultivar
Wild type (no specific ornamental or agricultural cultivars typically managed as turf)
Hardiness Zones
USDA Hardiness Zones 6 through 10, sensitive to hard frosts which top-kill the plant, though underground rhizomes survive to resprout in spring.
About This Grass
A large, coarse, erect perennial grass growing up to 3 to 7 feet tall. Features broad, bright green leaves with a prominent light-colored midrib and large, open, purplish panicle seed heads.
Blade Characteristics
Coarse blades, width typically 0.5 to 1.5 inches, flat shape with a pointed tip. Color is bright to medium green with a very prominent white midvein. Membranous ligule with a fringe of hairs, no auricles, rolled in the bud.
Root System
Deep, aggressive, and extensive fibrous root system combined with thick, fleshy rhizomes that store nutrients and allow rapid regeneration, making it drought-resistant and difficult to eradicate.
Growing Information
Origin Region
Native to the Mediterranean region and Asia; now naturalized worldwide in tropical, subtropical, and warm temperate regions
Growth Habit
Rhizomatous and stoloniferous, spreading aggressively both by underground rhizomes and extensive seed production, forming dense colonies
Sunlight & Water Needs
Requires full sun and thrives in high light conditions. Moderate to high drought tolerance once established due to deep roots and rhizomes, but grows most vigorously with adequate moisture. Adaptable to most soils.
Mowing & Maintenance
High maintenance if managed as a weed due to its aggressive spread; frequent close mowing can weaken it temporarily but rarely kills established rhizomes. Generally considered a noxious weed in turf settings.
Special Characteristics
High weed status due to fast growth and allelopathic properties; can cause prussic acid (cyanide) poisoning in livestock under certain stress conditions such as frost or drought. Highly resilient and invasive.
Ecological Information
Introduced species in North America, often classified as a noxious and invasive weed that crowds out native plants and crops. Provides minimal desirable wildlife cover and can disrupt local ecosystems.