Weed Seed: Lythrum salicaria (Purple loosestrife)

Family

Lythraceae

Common Name

Purple loosestrife

Regulation

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

Distribution

Canadian: Occurs in all provinces but not in the territories (Brouillet et al. 2016^Footnote 1).

Worldwide: Native to northern Africa, Europe and temperate Asia and introduced in North America, Chile, South Africa, Australia and New Zealand (USDA-ARS 2016^Footnote 2). It is found throughout the United States except for the extreme southeastern states; abundant in the northeastern region (Kartesz 2011^Footnote 3).

Duration of life cycle

Perennial

Seed or fruit type

Seed

Identification features

Size

• Seed length: 0.5 - 1.0 mm
• Seed width: 0.3 - 0.5 mm

Shape

• Teardrop or cuneate seed

Surface Texture

• Seed glistening with fine longitudinal striations

Colour

• Seed dark reddish-brown

Other Features

• Hilum is a black dot at the wide end of the seed
• A raphe extends from the hilum to the narrow end of the seed

Habitat and Crop Association

Pastures, meadows, old fields, gardens, wetlands, shores and disturbed areas (Darbyshire 2003^Footnote 4). Not usually a weed of agriculture but can grow along field edges near wetlands (CABI 2016^Footnote 5).

General Information

Purple loosestrife has been present in North America since the early 19th century, likely transported in ship ballast (Mal et al. 1992^Footnote 6). It may also have been planted as a medicinal herb, or brought by beekeepers as a source of nectar (Mal et al. 1992^Footnote 6).

It is available from some seed companies as an ornamental (CABI 2016^Footnote 5). Disturbed sites with moist soils or seasonally flooded sites are required for establishment (CABI 2016^Footnote 5).

Similar species

Hyssop loosestrife (Lythrum hyssopifolia)

• Seeds of hyssop loosestrife have a similar teardrop shape, prominent raphe and striated surface as purple loosestrife.
• Hyssop loosestrife seeds (length: 1.0 mm; width: 1.3 mm) are generally larger, a yellowish colour and not elongated as purple loosestrife.

Photos

Similar species