Sorghum halepense (L.) Pers.

Johnson Grass

Threat Level	Category
Established	Grass

Description

Stem

Grows to a height of 6 to 7 feet at maturity.

Leaves

Leaves are arranged alternately along a hairless, upward branching stem and have a distinct, white mid-rib.

Flowers

Blooms from May through October. The flower head is large, open, well branched and has an overall pyramid outline. Initially, it is green or greenish violet. At maturity it becomes a dark reddish or purplish brown.

Fruit

Reproduces by seed and underground stems. Seed bank remains viable up to five years.

Images

Photo: Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org
More images of Sorghum halepense

Life History

Johnson Grass is a warm-season perennial which spreads by seed and by a very extensive rhizome. Seeds are dispersed by wind, water, wildlife (especially birds), livestock, and contaminated crops, vehicles, and machinery. Up to 80,000 seeds and 8 kg of rhizomes can be produced by one plant in one growing season.

Habitat

Johnson Grass is native to the Mediterranean region of Europe and Africa, and possibly to Asia. Worldwide, its range as a weed extends from 55Â° N to 45Â° S in latitude.

Management Recommendations

Mechanical Control

Mechanical means are only practical in small applications by digging up plant and root wad with a shovel.

Prescribed fire is not recommended. Due to rhizome depths of 8 inches (20 cm) or more, Johnson Grass is likely to survive severe fire treatments.

Chemical Controls

Foliar Spray Method: A 2% mixture of Glyphosate is preferred. Herbicides are most effective on large infestations when incorporated into long-term management plans that include replacement of weeds with desirable species and proper timing of treatment to plant's life cycle. Control is most effective before plants have developed five leaves. It is important to prevent seeds from ripening and dispersing, kill seedlings and existing rhizomes, and prevent growth of new rhizomes.