Common Australian Garden Weeds

Sorghum halepense

Scientific name: Sorghum halepense (L.) Pers.


Habit of Johnson grass (Sorghum halepense).


A Johnson grass inflorescence during anthesis.


A close-up of the inflorescence of Johnson grass showing the purplish coloration of the spikelets.


A young Johnson grass plant.

Synonyms: Holcus halepense L.; Sorghum halepense forma muticum (Hackel) C.E. Hubbard

Common name: Johnson grass

Family: Poaceae

Origin:

Native of the Mediterranean region.

Habit:

Perennial grass with erect habit usually 1.8 m tall but growing up to 3 m, and developing extensive rhizomes.

Habitat:

Weed of cultivation, originally introduced as a fodder grass, it is difficult to control because it spreads via rhizomes.

General description:

Stems and leaves
Rhizomes are scaly, white or reddish. Stems are stout and erect 50-150 cm tall with nodes that can be hairless or tufted with downy hairs. The leaves are alternately arranges, hairless with a definite midrib and rough margins, 20-50 cm long. Young leaves are rolled in the bud.
Flowers and fruit
Inflorescences are pale green to purplish, consisting of many slender branches dividing into many finer branches. The entire inflorescence is around 35 cm long. Awns, if present, are twisted at the base and 1-2 cm long. They are deciduous, falling away readily. Seeds are egg-shaped, 3-4 mm long, reddish brown to black in colour, with a finely lined texture.

Distinguishing features:

Large robust grass with extensive white or reddish scaly rhizomes and alternately arranged leaves, 20-50 cm long with definite midrib and rough margins. Inflorescence is many branched, pale green to purplish in colour, and up to 35 cm long.

Noxious status:

Declared noxious in the Northern Territory and New South Wales. It is also a prohibited species in Western Australia.

Sources:

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of Primary Industries, Brisbane.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious Weeds of Australia. Inkata Press, Melbourne.

Stanley, T.E. and Ross, E.M. (1983-1989). Flora of South-eastern Queensland. Volume 3. Department of Primary Industries, Brisbane.

Anonymous. (2000). Noxious Weed List for Australian States and Territories. Prepared by the National Weeds Strategy Executive Committee.

Auld, B.A. and Medd, R.W. (1996). Weeds: An Illustrated Guide to the Weeds of Australia. Inkata Press, Sydney.