Johnsongrass
Family
PoaceaeScientific Name
Sorghum halepense
Synonyms (former Scientific Names):
Sorghum miliaceum
Holcus halepensis
Habit
Johnsongrass is a course, generally clumping grass, and one of the most troublesome perennial grasses in the U.S. Growth is surged by thick aggressive rhizomes and flowering last from June to July.
Leaves
The plant can grow 6 to 7 ft height. It has a fringed membranous ligule (2.0-5.5mm long). Leaf blades are 20 to 60 cm long and 10-30 mm wide at maturity and have a thick white midvein. The leaf blade and sheath are hairless beside a few sparse hairs near the collar.
Identifying Characteristics
Johnsongrass can spread through seed or rhizomes.
Flower Seed Head
The seedhead flowers May through October. The seedhead is an open panicle (12-50 cm long) with numerous branches and has an overall pyramid outline. The seedhead starts out green but by maturity it turns dark reddish or purple brown.
Seed Fruit
The seed is produced on the shorter floret which is 4-5.5 mm long. The seed itself is oval shaped, long dark reddish brown(3-5mm long).
Where Found
Johnsongrass prefers rich soils and doesn't tolerate close mowing. It grows in cultivated, reduced-tillage, and perennial cops.
Leaf Hair on Upper Surface
no hairs
Leaf Arrangement
rolled in bud
Mature Leaf Width
more than 15 mm
Stem
round
Seedhead
panicle
Life Cycle
perennial
Auricle
not present
Ligule
membrane
Ligule Length
Varies:
2-3 mm,
more than 3 mm
Plant Type
Grass