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Weed Seed: Sorghum halepense (Johnson grass)



Common Name

Johnson grass


Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.


Canadian: Present in ON (Brouillet et al. 2016Footnote 1).

Worldwide: Native range uncertain, possibly native to northern Africa and western and central Asia as far as India (Warwick and Black 1983Footnote 2, USDA-ARS 2016Footnote 3). Widely introduced elsewhere, including eastern Asia, North and South America, Europe, southern Africa, Australia and New Zealand (CABI 2016Footnote 4).

Duration of life cycle


Seed or fruit type


Identification features



Surface Texture


Other Features

Habitat and Crop Association

Cultivated fields, pastures, orchards, roadsides and disturbed areas (Darbyshire 2003Footnote 5, CABI 2016Footnote 4). A serious weed of many crops, notably cereals, corn, sorghum, soybeans, beans, cotton, rice, sugarcane, citrus and grapevine (CABI 2016Footnote 4).

General Information

Johnson grass was introduced into the southeastern United States as a forage crop in the early 19th century and then prompted weed control measures in the early 20th century (Warwick and Black 1983Footnote 2).

Johnson grass produces abundant seed (up to 28,000 seeds per plant) which are readily shed when mature and can be carried by wind or rain water (CABI 2016Footnote 4). Seeds can remain viable in the soil for at least seven years (CABI 2016Footnote 4). They also retain their viability after passing through the gut of animals such as birds or cattle (Warwick and Black 1983Footnote 2).

Similar species

Sudan grass (Sorghum bicolor subsp. drummondii)


Johnson grass (Sorghum halepense) spikelets
Johnson grass (Sorghum halepense) spikelet, inner side
Johnson grass (Sorghum halepense) spikelet, outer side
Johnson grass (Sorghum halepense) spikelet base, inner side
Johnson grass (Sorghum halepense) spikelet top showing margin teeth
Johnson grass (Sorghum halepense) caryopsis
Johnson grass (Sorghum halepense) spikelet (L) and caryopsis (R)

Similar species

Similar species: Sudan grass (Sorghum bicolor subsp. drummondii) spikelets
Similar species: Sudan grass (Sorghum bicolor subsp. drummondii) spikelet, inner side
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