Weed Seed: Anthemis cotula (Mayweed)

Family

Asteraceae

Common Name

Mayweed

Regulation

Secondary Noxious, Class 3 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.

Distribution

Canadian: Occurs across Canada except in NT and NU, although reports from SK and PE are questionable (Brouillet et al. 2016^Footnote 1).

Worldwide: Native to the Mediterranean region and widely introduced elsewhere including South Africa, Australia, New Zealand, parts of Europe, and North and South America (CABI 2016^Footnote 2, USDA-ARS 2016^Footnote 3). It is found throughout the United States, including Alaska and Hawaii (Kartesz 2011^Footnote 4, USDA-NRCS 2016^Footnote 5).

Duration of life cycle

Annual

Seed or fruit type

Achene

Identification features

Size

• Achene length: 1.0 - 2.3 mm
• Achene width: 0.8 - 1.0 mm

Shape

• Achene is wedge-shaped, tapering to the base

Surface Texture

• Achene tuberculate in longitudinal rows

Colour

• Achene straw yellow to brown

Habitat and Crop Association

Cultivated fields, pastures, gardens, lawns, railway lines, roadsides and disturbed areas (FNA 1993+^Footnote 6, Darbyshire 2003^Footnote 7, CABI 2016^Footnote 2). Found in most annual and many perennial crops, and most abundant in cereals and legumes (CABI 2016^Footnote 2). Particularly adapted to rich, wet soils and may be problematic in conservation tillage systems (CABI 2016^Footnote 2).

General Information

Mayweed seeds are most commonly spread by agricultural practices, and early infestations in cereal crops were thought to be largely via contaminated seed. Seeds may also be spread on agricultural equipment, and in hay, bedding, and animal manure.

Other accidental introductions are attributed to ship's ballast, and in some areas mayweed may have been introduced for medicinal or ornamental purposes. Individual plants may produce anywhere from 550-27,000 seeds depending on environmental conditions, and seed may remain viable for up to 25 years (CABI 2016^Footnote 2).

Similar species

Corn chamomile (Anthemis arvensis)

• The achenes of corn chamomile have a similar shaped and straw yellow colour as mayweed.
• Corn chamomile achenes (length: 2.3 - 2.8 mm; width: 1.5 mm) are generally larger than mayweed, and the surface is thick and ribbed rather than thin and tuberculate.

Photos

Similar species