Galeopsis ladanum L. - Red Hemp Nettle.
Systematic position.Family Lamiaceae, genus Galeopsis L.
Synonyms.Dalanum ladanum (L.) Dostal, Ladanum intermedium (Vill.) Slavikova.
Biological group.Annual germiniparous weed.
Morphology and biology.Stem is erect or ascending, angular, branched, with soft, downwardly adjacent hairs that do not thicken under nodes; up to 40 cm tall. Cotyledons are oval, full, with rounded tip and two distinct teeth at base. Leaves are short-petiolate, broad, ovate-lanceolate, crenulate, slightly pubescent or nearly hairless. Inflorescence is sparse, false whorl. Flowers are sessile, up to 6-10 per whorl. Calyx is 8-10 mm, slightly pubescent, with indistinct veins and pubescent teeth that are unequal in length. Corolla is 2 cm long; its tube is much longer than calyx, whitish; lower labia is lilac-purple with yellow spot and dark purple reticulation at fauces; its middle lobe is broadly obovate, 1.5-2 times broader than lateral lobes. Nutlets are obovate, with rounded tip, tapered toward base, smooth, dull. Color of nutlets is variegated, dark brown or brown-reddish, with light gray, dot-like spots. The weight of 1000 nutlets is 1.8-2g. The maximum fecundity of one plant is 7200 nutlets. Flowering period is June-September.
Distribution.Scandinavia, Central Europe, Asia Minor, and North America (adventive plant). European part of the former USSR, the Caucasus, Western Siberia, Eastern Siberia, the Far East, and northern regions of Central Asia.
Ecology.Grows on moist nutrient-rich and nitrogen-rich sands, loams, and peaty soils.
Economic significance.Weed of grain and tilled crops; occurs in fallow lands, kitchen gardens, wastelands, and along roads. Control measures include removing the stubble in early autumn followed by deep plowing, inter-row cultivation of tilled crops, and chemical weeding.
Related references:Agaev, M.G., ed. 1988. Main agricultural weeds in crops of the Leningrad Region. Catalogue of VIR world collection. Issue 468. Leningrad: VIR, 112 p. (in Russian).
Anonym. 1996. Weeds in sugar beet. Berlin: Hoehst Schering AgrEvo GmbH, 479 p. (in German, English, Russian, Ukrainian).
Keller, B.A., Lyubimenko, V.N., Mal'tsev, A.I., Fedchenko, B.A., Shishkin, B.K., Rozhevits, R.Yu. & Kamenskii, K.V., eds. 1934. Weed plants of the USSR. V. 4. Leningrad: AN SSSR, 414 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. 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. Atlas-synopsis of weeds. Kyiv: Urozhai, 72 p. (in Ukrainian).