Johnsongrass
Sorghum halepense · Warm-season, Perennial, C4
Grass Family
Poaceae, Panicoideae, Tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Forage/Pasture (marginal)
Variety / Cultivar
Common Johnsongrass (Wild type)
Hardiness Zones
USDA Zones 6-11; extremely heat tolerant; goes dormant and turns brown after the first hard frost.
About This Grass
A tall, coarse perennial reaching 3 to 8 feet in height. Features a bright white midrib on leaves and large, open, purplish panicle seed heads. Often found in ditches and agricultural margins.
Blade Characteristics
Coarse width (10-30mm), flat shape, pointed tip, light to medium green with a prominent white midrib; rolled in the bud (vernation); large membranous ligule with hairs; no auricles.
Root System
Deep and aggressive; features thick, scaly, cream-colored rhizomes that allow for rapid spread; low thatch but extremely difficult to eradicate once established.
Growing Information
Origin Region
Native to the Mediterranean region; naturalized across most of the continental United States
Growth Habit
Rhizomatous (aggressive underground spreading) and clump-forming
Sunlight & Water Needs
Full Sun; high drought tolerance; thrives in fertile, well-drained soils but adaptable to various conditions; ph 5.5-7.5.
Mowing & Maintenance
Not typically mowed for turf; controlled via frequent cutting to prevent seed production; high maintenance if trying to eradicate; rarely fertilized intentionally.
Special Characteristics
Highly invasive; can produce toxic cyanide (prussic acid) in foliage after frost or drought, making it dangerous for livestock; excellent erosion control but crowds out all native species.
Ecological Information
Introduced/Invasive status in the US; limited wildlife value as it monocultures landscapes; companion grasses include other hardy pasture species like Tall Fescue, though it often displaces them.