Weeds
Galeopsis tetrahit L. - Bristle-Stem Hemp Nettle, Common Hemp Nettle.
Systematic position.
Family Lamiaceae, genus Galeopsis L.Biological group.
Annual germiniparous weed.Morphology and biology.
Stem erect, usually ramified, angular, covered with downward-tilted bristles, with conspicuously thickened nodes, up to 100 cm tall. Cotyledons large, oval, full, with rounded, slightly retracted tip, with two tips at base. Leaves oblong-ovate to lanceolate, acuminate, dentate along edges, with notched venation, petiolate; petioles red-brown. Flower markedly bilabiate, crown-shaped, located in axil, usually purple, infrequently white. Corolla approximately 1.5 cm long, pubescent on the outside; its tube somewhat longer than teeth of calyx; upper labia oval; middle lobe of the lower labia quadrangular or oblong, wide (2-4 mm) and flat, with bright yellow spot at fauces and a net-like pattern. Nutlets obovate, 2.75-3 mm long, 2-2.25 mm wide, somewhat flattened, finely tuberculate, dark gray or with black marble pattern. 1000 nutlets weigh 4.5-5.0 g. The maximum fruitfulness of one plant is 3000 nutlets. Seeds maintain their germinating capability in soil for 15 years. Flowering takes place in July-September.Distribution.
Scandinavia, Western Europe, the Mediterranean, North America (adventive plant). European region of the former USSR, the Caucasus, Western Siberia, Eastern Siberia, the Far East, Central Asia.Ecology.
Grows on rich, nitrogen-containing soils with high ground water levels; abundant in lower places.Economic significance.
Weed of grain and tilled crops and fodder grasses; occurs in kitchen gardens, along roads, in wastelands, in fallow lands, and near habitations. Control measures include removing stubble, followed by deep early autumn plowing, inter-row cultivation of tilled crops, and chemical weeding.Related references:
Anonymous. 1996. Weeds in sugar beet. Berlin: Hoehst Schering AgrEvo GmbH, 479 p. (in German, English, Russian, Ukrainian).Shishkin, B.K., ed. 1954. Flora of the USSR. V. 21. Moscow & Leningrad: AN SSSR, 704 p. (in Russian).
Ulyanova, T.N. 1988. Weed plants in the flora of Russia and other CIS states. St. Petersburg: VIR, 344 p. (in Russian).
Veselovskii, I.V., Lysenko, A.K., & Man'ko, Yu.P. 1988. The atlas and identification book on weeds. Kiev: Urozhai, 72 p. (in Ukrainian).