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Weed Seed: Digitaria spp. (Crabgrass)

Family

Poaceae

Common Name

Crabgrass

Regulation

Secondary Noxious, Class 4 and Noxious, Class 5 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.

Distribution

Canadian: The genus includes 3 species found in Canada, distributed across Canada with the exception of NL and the territories (Brouillet et al. 2016Footnote 1).

Worldwide: The genus contains about 250 species originating from tropical and warm temperate parts of the world (Mabberley 2008Footnote 2). It includes cultivated and weedy species, some widely introduced around the world (USDA-ARS 2016Footnote 3).

Duration of life cycle

Most species annual; some perennial

Seed or fruit type

Spikelet

Identification features

Size

Shape

Surface Texture

Colour

Other Features

Habitat and Crop Association

Cultivated fields, pastures, gardens, lawns, orchards, vineyards, shores, roadsides, railway lines and disturbed areas (Darbyshire 2003Footnote 4, CABI 2016Footnote 5). Weedy species infest a variety of crops worldwide and are problematic in lawns (CABI 2016Footnote 5).

General Information

The three species occurring in Canada are: large crabgrass (Digitaria sanguinalis), smooth crabgrass (D. ischaemum) and fall crabgrass (D. cognata) (Darbyshire 2003Footnote 4, Brouillet et al. 2016Footnote 1). The first two have been introduced into Canada and the third is native (Darbyshire 2003Footnote 4).

Crabgrasses are problem weeds in sandy and loam soils (Darbyshire 2003Footnote 4, CABI 2016Footnote 5). Large crabgrass plants can produce approximately 150,000 seeds in a growing season and mature plants spread over large areas by tillering soon after establishment (CABI 2016Footnote 5).

Similar species

Genera from the same tribe as Digitaria spp., Paniceae, have certain features that distinguish them from other tribes in the Poaceae:

Within the Paniceae tribe, Digitaria spp. have distinguishing features:

Photos

Southern crabgrass (Digitaria ciliaris) spikelets
Smooth crabgrass (Digitaria ischaemum) spikelets
Large crabgrass (Digitaria sanguinalis) spikelets
Large crabgrass (Digitaria sanguinalis) spikelet, outer side
Large crabgrass (Digitaria sanguinalis) spikelets, inner side
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