Johnson Grass
Sorghum halepense · Warm-season, Perennial, C4
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Forage (with precautions), Erosion Control
Variety / Cultivar
Common wild type (Sorghum halepense)
Hardiness Zones
USDA Zones 6-10; thrives in heat; kills back to ground in winter (dormancy) but rhizomes survive deep freezes.
About This Grass
An aggressive, tall-growing perennial grass that often reaches 3-7 feet if left unmowed. It features light green to medium green foliage with a prominent white midvein. Seed heads are large, open, purple-tinted panicles. Base of the stems often shows reddish or purplish pigmentation.
Blade Characteristics
Coarse width (10-30mm), flat shape, pointed tip, medium green with a stark white midrib; rolled vernation in the bud, short membranous ligule with hairs, auricles absent.
Root System
Extensive and fleshy rhizome system, deep fibrous roots; high thatch potential, extremely fast establishment; high drought tolerance and rapid recovery.
Growing Information
Origin Region
Mediterranean region; widely naturalized across North America and tropical/subtropical globally
Growth Habit
Rhizomatous (aggressive creeping underground stems) and bunch-forming; rapid lateral spread
Sunlight & Water Needs
Full Sun (minimal shade tolerance); moderate water needs but extreme drought tolerance; thrives in heavy clay to sandy loams, pH 5.5-7.5.
Mowing & Maintenance
Not recommended for turf; if in pasture, mow at 4-6 inches to prevent seed head formation; high maintenance to eradicate; resistant to many standard mowing frequencies.
Special Characteristics
Highly invasive; salt-tolerant; extreme traffic tolerance; can become toxic (prussic acid/cyanide) to livestock after drought or frost.
Ecological Information
Introduced/Invasive in North America; provides some cover for small mammals; excellent soil stabilizer but outcompetes native vegetation; problematic weed in agricultural crops.