Macquarie Valley Weeds Committee & Lachlan Valley Weeds Advisory Committee


Johnson Grass

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Botanical Name: Sorghum halepense
Other Common Names:


Class Regions
Class 3Bogan Shire Council,Bourke Shire Council,Brewarrina Shire Council,Cabonne Council,Castlereagh Macquarie County Council,Central Darling Shire Council,Cobar Shire Council,Cowra Council,Forbes Shire Council,Lachlan Shire Council,Mid-Western Regional Council,Narromine Shire Council,NSW DPI - Lands - Far West Region,Orange City Council,Parkes Shire Council,Upper Macquarie County Council,Weddin Shire Council,Wellington
Class 4Bland Shire Council,Cootamundra Shire Council,Dubbo Regional Council
Landholder Responsibilities: Class 4 - growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority and the plant may not be sold, propagated or knowingly distributed. Class 3 - The plant must be fully and continuously suppressed and destroyed
Why Is It Bad?: Decreases in production through increases in pests affecting seed sorghum crops, as Johnson Grass harbours the sorghum midge. Decreases in production through increases in pests affecting sugar cane crops, as Johnson Grass acts as a host for sugar cane mosaic virus. Contamination of seed sorghum crops from Johnson Grass pollen. Increased stock losses as consumption of Johnson Grass can cause hydrocyanic acid poisoning in grazing animals such as sheep or cattle. Increased stock losses as consumption of Johnson Grass rhizomes can cause fatalities in pigs. Decreases in biodiversity, especially on roadsides, as Johnson Grass is a vigorous competitor. Increases in infestation sizes and distributions as Johnson Grass spreads quickly, especially after cultivation or grading. Decline of health of asthma suffers during peak pollen times


Habit: Grass
Leaves: Leaves are flat, with a prominent midrib, up to 45cm long and 5-50mm wide. They are light green, sometimes purple-red when stressed.
Flowers: Inflorescences are open, 25-45cm long. Spikelets are purplish and paired.
Fruit: Seeds are 4-5mm in length, hairy and orange-red in colour. A single plant can produce 80,000 seeds.
Roots: Roots are rhizomatous.

Control Methods

Manual Removal: All parts of the plant must be removed as regrowth occurs easily from fragmented rhizomes
Chemical Use: Only registered herbicides should be used. Spot spraying is effective selective control. A wick wiper can be used in situations where Johnson Grass is growing taller than desired species.
Slashing & Cutting:
Biological Control:
Cultivation & Scalping: Not generally recommended as it can cause high levels of root fragmentation. However, crop rotation can help to smother Johnson grass infestations. Tillage should cut and bring rhizomes to the surface for desiccation rather than distributing the fragments throughout the site. Crops should include winter-annual small grains and legume forages to smother and out-compete Johnson Grass.
Monitoring: Successful treatment programs rely on ongoing monitoring of sites. Regrowth and new seedlings can easily become larger infestations if follow-up treatments are not part of the management program.


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Image Credit: John Ryan

Image Credit: John Ryan

Image Credit: John Ryan

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