Weed Seed: Persicaria perfoliata (Devil's-tail tearthumb)
Invasive Plant - Devil's-tail tearthumb (Persicaria perfoliata)
Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order, 2016 under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.
Listed on the List of Pests Regulated by Canada established under the Plant Protection Act.
Canadian: Previously reported from BC but did not persist (CFIA 2012Footnote 1).
Worldwide: Native to eastern Asia and introduced to Turkey, the West Indies and the United States, where it is found in the northeastern states and in Oregon (CFIA 2012Footnote 1, USDA-ARS 2016Footnote 2).
Duration of life cycle
Seed or fruit type
Achene, may be in a perianth
- Achene length: 3.4 - 4.0 mm
- Achene width 3.5 - 3.8 mm
- Seed diameter: 3.0 - 3.5 mm
- Achene is spherical, slightly three-angled at the top with a white dot of tissue
- Achene is smooth, glossy
- Perianth is thick and dull; wrinkled in dried specimens
- Perianth is dark bluish-purple when fresh, fades to a light bluish-purple when dried
- Achene is black, rarely fading into straw yellow at the base
- Seed inside is chalk-white with reddish seed coat
- The achene retains perianth tissue at the base
Habitat and crop association
Riparian areas as well as a wide variety of disturbed areas, including roadsides, hedges, fields, pasture and forest edges, early successional forests, plantations, gardens and parks (CFIA 2012Footnote 1).
Devil's-tail tearthumb was introduced into the eastern United States in the 1940s with contaminated nursery stock (Poindexter 2010Footnote 3). It prefers moist to wet soils and is known for its rapid growth as well as its ability to suppress other species by smothering or shading (CABI 2016Footnote 4). Large infestations of devil's-tail tearthumb hamper movement due to its dense prickles (CABI 2016Footnote 4).
Halberdleaf tearthumb (Persicaria arifolia)
- Similar size, black achene colour, glossy achene surface and thick perianth as devil's-tail tearthumb.
- Halberdleaf tearthumb's perianth is not as thick and the achene is compressed and slightly pointed at the top compared to devil's-tail tearthumb.
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