Viola tricolor L. - Garden violet.
Taxonomy.Family Violaceae, Genus Viola.
Biology type.Annual or biennial.
Morphology and biology.Plant height is about 10-15 cm; stems are lightly elbow-shaped, covered by short, plumpish and down deflected hairs; pinnatiparite stipules with large final lobe, 3-28 mm long, hairy; leaves are various in shape. Flowers about 1.5 cm in length with comparatively long pedicles (5-7 cm), which horizontally deviate on the fruits; bracts are awl-shaped. Sepals are linearly-lanceolate, about 1 cm in length, sharp, with densely ciliated edges and short hairs on outer edge, with ovate, angular appendages. Corolla is 18-27 mm in length, petals are various in color with upper petals dark-blue to violet, lateral petals ovate, and basal petal always yellow or yellow-pale with 3 to 7 dark stripes, violet-pale at the edge, spur is not long, narrow and turned upward. Boll is oblong-ovate, 5-7 mm in length. Seeds are obovate, about 1.5 mm in length, tan-colored. Flowering occurs from April until October, fruiting from July until August. Production of plant reaches up to 3020 seeds. Seeds keep their germinating capacity in soil up to 6 years and stay in dormancy over a period of 6-8 months.
Distribution.Scandinavia, Atlantic and Central Europe, center and south of the European part of the former USSR, Siberia.
Ecology.Light-requiring plant of open inhabitances bears only slight shading. Prefers medium-wetted soils, but can be found in more dry or moist places. Grows on sufficiently fertile, sub-acid and even neutral soils (pH 6.0-7.5). Seldom occurs on infertile, acidic (pH 5.0-5.5), leached, sandy, and clay sandy soils. Does not compete favorable with other plant species. Seedlings appear from a depth of at most 4-5 cm. Minimum temperature for germination is 2-3°C, optimum; 18-24 °C.
Economic value.It occurs mainly among spring cereals and tilled crops. Control measures: stubbly shelling following winter tillage, pre-sowing harrowing done at the proper time. For tilled crops: inter-row treatments. Chemical control when necessary.
Reference citations:Chikov, P.S., ed. 1983. Atlas of distributions and resources of medicinal plants of the USSR. Moscow. 319 p.
Fisyunov A.V. 1984. Handbook of weed control. Moscow: Kolos. 225 p.
Komarov, V.L., ed. 1935. Flora of the USSR. Leningrad: Acad. Sci. USSR. V. 15: 462.