Weed Seed: Ambrosia artemisiifolia (Common ragweed)

Family

Asteraceae

Common Name

Common ragweed

Regulation

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

Distribution

Canadian: Occurs across Canada except in NU and YT (Brouillet et al. 2016^Footnote 1).

Worldwide: Native to North and South America, and widely introduced elsewhere including Europe, Africa, temperate and tropical Asia, Australasia and the Pacific Islands (USDA-ARS 2016^Footnote 2). Widely distributed in North America with both native and introduced populations present in the U.S. and Canada (Brouillet et al. 2016^Footnote 1, USDA-NRCS 2016^Footnote 3).

Duration of life cycle

Annual

Seed or fruit type

Achene within a bur

Identification features

Size

• Bur length: 1.9 - 3.7 mm
• Bur width: 1.5 - 2.8 mm
• Achene length: 1.5 - 3.0 mm
• Achene width: 1.5 mm

Shape

• Bur and achene are obovate 

Surface Texture

• Bur is dull, woody

Colour

• Bur is dark grey with purple streaks
• Achene is brown

Other Features

• Bur has a ring of several spines near top approximately 0.5 mm long and an apical spine approximately 1.5 mm long

Habitat and Crop Association

Cultivated fields, fencerows, pastures, shores, canals, quarries, railway lines, roadsides, wasteland and disturbed areas (FNA 1993+^Footnote 4, Darbyshire 2003^Footnote 5, CABI 2016^Footnote 6). Found in a range of both agronomic and horticultural crops, particularly in cereals and cultivated row crops (Basset and Crompton 1975^Footnote 7, CABI 2016^Footnote 6). Often present as a dominant species in early succession of uncultivated areas (CABI 2016^Footnote 6).

General Information

Seeds of common ragweed are commonly found in stored and transported grains, and have been dispersed around the world as contaminants in seed and grain crops, including cereals, oilseeds and bird seed.

A single plant typically produces 3,000 - 4000 seeds, although up to 32,000 seeds per plant have been reported. Seeds remain viable for up to 40 years (CABI 2016^Footnote 6).

Similar species

Perennial ragweed (Ambrosia psilostachya)

• Perennial ragweed burs are a similar size, obovate shape and grey colour as common ragweed.
• Perennial ragweed burs have smaller spines, or only an apical spine that may be broken off, and may lack the purple streaks of common ragweed burs.
• If the burs are removed, it is difficult to distinguish between common and perennial ragweed achenes.

Photos

Similar species