Lamium L.
(incl. Galeobdolon Adans., Lamiastrum Heister ex Fabr.)
Lamium is here treated in a broad sense and includes Lamiastrum (see Mabberley 2008). In the past years this taxonomic viewpoint was no longer followed by many taxonomists (e.g. Jäger & Werner 2005, van der Meijden 2005, Sell & Murrell 2009, Stace 2010). Lamiastrum counts one very variable species with creeping stems and yellow corollas. Mennema (1989) accepted the latter as a subgenus of Lamium (subgenus Galeobdolon). However, his classification is not corroborated by molecular studies and should be abandoned. Although morphologically very distinct Lamiastrum is perhaps better included in Lamium. A large clade of Lamium (including L. galeobdolon) is strongly supported by molecular data (Bendiksby & al. 2011). Krawczyk & al. (2013) found out that both taxa are indeed genetically not distant enough to be considered separate genera, and integration of Galeobdolon and Lamium is legitimate. Even then, Lamium is not monophyletic: Wiedemannia should be included in it (see also Ryding 2003) and some of the species currently accommodated in Lamium should be resurrected (Bendiksby & al. 2011).
In its broad sense Lamium comprises about 20-30 species in Eurasia and North Africa. Six species are native in Belgium: Lamium album L., L. amplexicaule L., L. galeobdolon (at least the subsp. galeobdolon and subsp. montanum (Pers.) Hayek), L. hybridum Vill., L. maculatum L. and L. purpureum L. (Lambinon & Verloove 2012). Out of these Lamium galeobdolon and L. maculatum are also cultivated for ornament and regularly occur in areas where they are not native (wood margins, road verges, dumps, etc.). Cultivated races of both slightly or considerably differ from native races. Lamium galeobdolon is further discussed below. For the variability of Lamium maculatum one can refer to Tait (1985). Some additional species, some of which have been recorded as aliens or escapes from cultivation (L. garganicum and L. orvala), are grown for ornament (Grant 2000, Jäger & al. 2008).
1 Corolla yellow. Stem creeping, rooting at the nodes. Perennial === Lamium galeobdolon
Corolla pink, purple or white. Stem erect or ascending, not rooting at the nodes. Annual or perennial === 2
2 Anthers glabrous. Corolla 25-45 mm, with straight tube. Perennial === L. orvala
Anthers hairy. Corolla often less than 25 mm (if longer, then tube curved). Annual or perennial (native) === Lamium album, L. amplexicaule, L. hybridum, L. maculatum and L. purpureum
Additional alien: Lamium garganicum L. subsp. garganicum (SE-Eur., garden escape?). This species persisted for some time (at least between 1906 and 1920) on a shady off-ramp in Ukkel.
Literature:
Ball P.W. (1972) Lamium. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 3. Cambridge University Press, Cambridge: 147-148.
Bendiksby M., Brysting A.K., Thorbek L., Gussarova G. & Ryding O. (2011) Molecular phylogeny and taxonomy of the genus Lamium L. (Lamiaceae): Disentangling origins of presumed allotetraploids. Taxon 60(4): 986-1000.
Bendiksby M., Thorbek L., Scheen A.-C., Lindqvist C. & Ryding O. (2011) An updated phylogeny and classification of Lamiaceae subfamily Lamioideae. Taxon 60(2): 471-484.
Gorshkova S.G. (1977) Lamium. In: Shishkin B.K. (ed.), Flora of the U.S.S.R., vol. XXI. Academy of Sciences of the USSR: 88-100.
Grant M.L. (2000) Lamium. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 194-195.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Jäger E.J. & Werner K. (eds.) (2005) Rothmaler Band 4. Exkursionsflora von Deutschland. Gefässpflanzen: Kritischer Band. Springer Verlag, Berlin: 880 p.
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Krawczyk K., Korniak T. & Sawicki J. (2013) Taxonomic status of Galeobdolon luteum Huds. (Lamiaceae) from classical taxonomy and phylogenetics perspectives. Acta Biologica Cracoviensia, Series Botanica 55(2): 18-28. [available online at: http://www2.ib.uj.edu.pl/abc/pdf/55_2/02_krawczyk.pdf]
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Mennema J. (1989) A taxonomic revision of Lamium (Lamiaceae). Bot. Ser. n° 11, Leiden. [available online at: https://www.repository.naturalis.nl/document/551107]
Mill R.R. (1982) Lamium. In: Davis P.H. (ed.), Flora of Turkey and the East Aegean Islands, Vol. 7. Edinburgh University Press, Edinburgh: 126-148.
Pujadas Salva A.J. (2006) Consideraciones sobre el género Lamium (Lamiaceae) en “Flora Iberica”. Acta Bot. Malacitana 31: 223-229. [available online at: http://www.biolveg.uma.es/abm/Volumenes/vol31/31-N-PUJADAS.pdf]
Ryding O. (2003) Reconsideration of Wiedemannia and notes on the circumscription of Lamium (Lamiaceae). Bot. Jahrb. 124(3): 325-335.
Sell P. & Murrell G. (2009) Flora of Great Britain and Ireland. Vol. 3 Mimosaceae – Lentibulariaceae. Cambridge University Press, Cambridge: XXVIII + 595 p.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Tait W.A. (1985) Lamium maculatum and its cultivars. The Garden 110: 291-292.
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.