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SEASONAL IDENTIFICATION
JOHNSONGRASS (Sorghum halapense)
LATE
SPRING
EARLY
-
MIDSUMMER
LATE
SUMMER
-
EARLY
FALL
EARLY
-
MIDSUMMER
LATE
SUMMER
LATE
SUMMER
-
FALL
Johnsongrass seedlings with broad leaf blades emerge later
than most Ohio grasses. White midrib is visible at this stage.
Johnsongrass grows approximately 2–4 feet tall before
flower/seed head formation. This growth stage is known as
boot-to-head. Chemical control is ideal at this stage.
Note the open arrangement on the symmetrical,
pyramid-shaped flower/seed head. Seed husks turn reddish
purple as seeds develop.
The leaf blades wrap around the stem, and if detached
display white center midribs and a tattered, translucent
membrane.
After seed head formation, Johnsongrass grows up to 8 feet
tall. These dense colonies are formed by rhizomes.
Patches of Johnsongrass can be seen in unmowed areas
in fall but rarely into winter. Identification relies on open
arrangement of seedhead. Seeds are oval shaped, shiny,
and brown and are covered in coarse hairs.
