Johnson Grass

North Africa, West Asia, Southern Europe

General description

Perennial, summer grass stout erect stems <300cm high, creeping rhizomes <1m deep. Leaf blades flat, alternate, often purple blotched, whitish midrib on underside. Leaf sheaths ribbed, often hairy on inside, ligules papery. Large pyramidal hairy purplish flowerhead <50cm long. Seed dark light brown. Can produce 80,000 seeds per season, and remain viable for <30 months. Seedlings closely resemble maize or millet.

Arable land, pasture, waste places, roadsides. Grows in wide range of conditions, favours warm, humid areas with summer rainfall. Foliage frost-tender but rhizomes tolerate two days of soil temperatures less than -3ºC.

Seeds spread by water, birds, animals & contaminated seed stock. Spreads locally via long rhizomes, also readily spread by cultivation.

Forms dense spreading patches, completely smothering other grasses, crops. Toxic to livestock, esp. in adverse growing conditions or new growth.

Site management

All sites must be quarantined to prevent movement of seed and rhizomes.

Recommended approaches

Under official control. Control work only to be carried out by persons authorised by MAF Biosecurity New Zealand.

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

RPMS status

Surveillance - Whole Region
Johnson grass - Main species image