Johnson Grass

Sorghum halepense

Keys to Identification

  • Up to 10 feet tall perennial grass
  • With tillers from the crown

Family

Poaceae – Grass Family

Other Names

n/a

USDA Code

SOHA

Legal Status

Colorado Noxious Weed List C

Identification

Lifecycle

Perennial

Growth form

Grass

Flower

Panicle is a 4-20 inch pyramid shape. Young flowers are pale green but are a dark purple when mature.  July – frost

Seeds/Fruit

Yellow to purple in open spreading seedhead, 1/8-3/16 inches long.  Up to 28,000 seeds per plant

Leaves

Flat and hairless, leaf buds are rolled.  Distinctive light colored midrib.  12-30 inches long, 1/2-1 inch wide

Stems

Erect and unbranched.  Solid with swollen nodes

Roots

Fibrous roots and coarse rhizomes that may grow up to 6 feet long

Similar Species

Exotics

 

Natives

 

Impacts

Agricultural

Invades cropland, reducing yields by 30-40%.  May be poisonous to livestock under stress conditions

Ecological

Reduces native flora and displaces broadleaf species. Grows rapidly and competes aggressively

Habitat and Distribution

General requirements

Prevalent in riverbank communities, disturbed sites, and moist, well-drained soils. Requires warm season moisture

Distribution

Widespread in North America

Historical

Native to the Mediterranean 

Biology/Ecology

Life cycle

Perennial

Mode of reproduction

Seed, rhizomes and plant fragments

Dispersal

Through contaminated seed, hay, and equipment.  May be spread by animals and birds

References

Weed Control in Natural Areas in the Western United States. University of California Weed Research and Information Center. Pg 380-381 USDA. (2020). Johnsongrass
USDA. (2019). Johnsongrass. USDA NRCS Plant Guide

High Plains Integrated Pest Management – https://wiki.bugwood.org/HPIPM:Johnsongrass

 

 

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