Mentha canadensis L. - Japanese Mint.
Systematic position.Family Lamiaceae, genus Mentha L.
Synonyms.Mentha haplocalyx Briq., Mentha sachalinensis (Briq.) Kudo, Mentha arvensis subsp.piperascens (Malivaud ex Holmes) Hara.
Biological group.Perennial rhizome weed.
Morphology and biology.Plant is 40-60 cm high, stems are striated, hairy in upper part, hairy only on ribs in lower part, simple, more seldom slightly ramified. Leaves are petiolate, oblong or oblong-lanceolate, 3-8 cm in length, 8-30 mm in width, sparsely dentate-serrate along margin, acuminate, short hairy, with glandules above and below. Bracts are longer than peduncles and calyxes, ciliated, lanceolate-linear. Inflorescences are sessile dense multiflorous false whorls. Calyx is tubular-belled, about 2.5 mm in length, 2-3 times shorter than the tube, with narrow pointed linear-subulate teeth. Corolla is blue-violet, hairy on the outside, about 4 mm in length; its upper labia is deeply bilobed; lower labia has three equal oblong blunt lobes. Nutlets are 1 mm in length, 0.5 mm in width, oblong, with sharp keel. Flowering period is July-August.
Distribution.Northern China, Korea, Japan, North America. Western Siberia, Eastern Siberia, the Far East.
Ecology.Prefers rather moist locations. Grows well on sandy soils and clayey loams.
Economic significance.Weed of grain and tilled crops, soy, fodder grasses; occurs in fallow lands, kitchen gardens, waste lands, along roads. Control measures include multiple-field crop rotation, plowing-in of stubble, harrowing of winter crops, interrow cultivation of tilled crops, chemical weeding.
Related references:Nikitin, V.V. 1983. Weed plants of the USSR flora. Leningrad: Nauka, 454 p. (in Russian).
Shishkin, B.K., ed. 1954. Flora of the USSR. V.21. Moscow-Leningrad: AN SSSR, 704 p. (in Russian).
Ulyanova, T.N. 1998. Weed plants in the flora of Russia and other CIS states. St.-Petersburg: VIR, 344 p. (in Russian).