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. 2016Footnote 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 2016Footnote 2, USDA-ARS 2016Footnote 3). It is found throughout the United States, including Alaska and Hawaii (Kartesz 2011Footnote 4, USDA-NRCS 2016Footnote 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 2003Footnote 7, CABI 2016Footnote 2). Found in most annual and many perennial crops, and most abundant in cereals and legumes (CABI 2016Footnote 2). Particularly adapted to rich, wet soils and may be problematic in conservation tillage systems (CABI 2016Footnote 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 2016Footnote 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
