Johnsongrass
Sorghum halepense · Warm-season, Perennial, C4 grass
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Pasture/Forage, Erosion Control
Variety / Cultivar
Wild type, no specific commercial turf cultivar
Hardiness Zones
USDA Hardiness Zones 6 through 10. Highly sensitive to frost, going dormant or dying back in winter in cooler regions, but surviving underground via hardy rhizomes.
About This Grass
Tall, coarse perennial grass reaching 3 to 7 feet or more in height when unmowed. Features prominent upright stems, coarse texture, light to medium green leaves with a noticeable whitish midvein, and large, open, reddish-purple panicle seed heads.
Blade Characteristics
Coarse blades greater than 4mm in width (typically 0.5 to 1.5 inches wide), flat, with pointed tips and a prominent white midrib. Rolled in the bud (vernation). Ligule is a membranous fringe with hairs; auricles are absent.
Root System
Deep, aggressive root system featuring thick, fleshy rhizomes that spread rapidly. Fast establishment from seed and rhizome fragments, creating moderate thatch and dense underground networks that make eradication difficult.
Growing Information
Origin Region
Native to the Mediterranean region and parts of Asia; naturalized worldwide in tropical, subtropical, and warm temperate regions
Growth Habit
Aggressive rhizomatous and stoloniferous, forming dense clumps and extensive underground root networks
Sunlight & Water Needs
Requires full sun for optimal growth. Moderate to high drought tolerance once established due to deep roots. Thrives in fertile, moist soils but highly adaptable to poor soils and various pH levels.
Mowing & Maintenance
High maintenance if managed as a weed, as it grows rapidly and withstands frequent cutting by sending up new shoots from rhizomes. Difficult to control with mowing alone; typically requires selective herbicides.
Special Characteristics
Exceptional weed competitiveness and invasive potential. Can be toxic to livestock (produces prussic acid/cyanogenic glycosides) under certain conditions like frost or drought stress. High heat tolerance.
Ecological Information
Introduced invasive species in many parts of the world, particularly North America. Can crowd out native vegetation and disrupt agricultural crops. Provides limited cover for wildlife but generally regarded as a noxious weed.