Lamium galeobdolon (L.) L. subsp. argentatum (Smejkal) J. Duvigneaud (syn.: L. galeobdolon subsp. galeobdolon f. argentatum (Smejkal) Mennema, L. galeobdolon cv Florentinum, L. montanum (Pers.) Kabath var. florentinum (Silva Tar.) Buttler et Schiffmann, L. argentatum (Smejkal) Henker ex Loos, Lamiastrum galeobdolon (L.) Ehrend. et Polatschek subsp. argentatum (Smejkal) Stace, Lamiastrum argentatum (Smejkal) Soják, Galeobdolon argentatum Smejkal) (Cult.) – A fairly common and much increasing, invasive garden escape. Already collected in 1897 in Spa but the specimen originated in a garden and might as well be planted. The escape and spread of subsp. argentatum probably began in the 1970s. Alas, its invasion history is poorly documented and it was merely neglected for quite a long time. It was collected in wood margins in Péruwelz in 1975 and in Fonds-de-Leffe in 1985. Leten (1988) and Duvigneaud (1990) were the first to provide an overview of recent records and emphasized its naturalization in Belgium. In the past decades it was increasingly dumped in wood margins (it is often too vigorous for the garden). It then readily naturalizes and starts to spread, mostly clonally. By now it is common in many parts of Belgium (see for instance Thoen & Lamury 1999, Verloove 2002, Van den Bremt 2006). It is much less demanding than the native subspecies and occurs also in areas where the others are absent.
Subsp. argentatum is probably a mere cultivar of subsp. montanum. It is more vigorous and larger in all its floral parts and always (all year round) has distinct white blotches on all leaves (such blotches often occur on some leaves in the other subspecies as well but they are much less distinct and only temporarily).
Selected literature:
Duvigneaud J. (1990) Quelques observations floristiques effectuées à proximité du château de Houx (Yvoir, province de Namur, Belgique). Nat. Mosana 43(1): 10-14.
Eber W. (1999) Vergleichende Untersuchungen an Sippen des Lamium galeobdolon agg. mit besonderer Besücksichtigung von Lamium endtmannii. Florist. Rundbr. 33: 114-129.
Grenier E. (1994) A propos de Lamium galeobdolon (L.) L. Monde Pl. 89(450): 11-12.
Leten M. (1988) Lamium galeobdolon S.L. : een taxonomisch en nomenclatorisch kluwen. IFBL-contacblad 6(1): 8-16.
Lienenbecker H. (1981) Die Verbreitung der Goldnessel-Kleinarten (Lamiastrum galeobdolon agg.) in Ostwestfalen. Natur und Heimat 41: 55-58.
Loos G.H. (1997) Zur Taxonomie der Goldnesseln (Lamium L. subgen. Galeobdolon (Adans.) Aschers.). Florist. Rundbr. 31: 39-50. [available online at: http://species-id.net/o/media/e/e6/Flor.Rundbr._31%2C39-50_Loos_1997_Lamium_Galeobdolon.pdf]
Loos G.H. (1998) Lamium subgen. galeobdolon. Die Goldnesselgruppe in Thüringen: Anmerkungen und vorläufiger Bestimmungsschlüssel. Inform. Flor. Kart. Thüringen 14: 8-9.
Mattern A. (1994) Gartenwurdige europäische Taubnesseln. Gartenpraxis 20(2): 8-15.
Rutherford A. & Stirling A.M. (1987) Variegated archangels. B.S.B.I. News 46: 9-11. [available online at: http://archive.bsbi.org.uk/BSBINews46.pdf]
Thoen D. & Lamury J. (1999) Parc Naturel de l’Attert. Observations floristiques récentes (période 1993-1997). Adoxa 22: 21-28.
Rosenbaumová R., Plačková I. & Suda J. (2004) Variation in Lamium subg. Galeobdolon (Lamiaceae) - insights from ploidy levels, morphology and isozymes. Pl. Syst. Evol. 244(3-4): 219-244.
Van den Bremt P. (2006) Lamium galeobdolon. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 518.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Walter E. (1992) Die Silber-Goldnessel (Galeobdolon argentatum Smejkal), ein bisher weitgehend unbeobachteter Kulturflüchtling - auch in Oberfranken. Ber. Naturforsch. Ges. Bamberg 67: 23-35.
Walter E. (1995) Die Silber-Goldnessel (Galeobdolon argentatum SMEJKAL) - eine verwildernde, im Gelände leicht zu erkennende neue Pflanzensippe. Florist. Rundbr. 29(2): 125-128.
Wittmann H. & Strobl W. (1986) Zur Kenntniss der Gattung Galeobdolon Adans. im Bundesland Salzburg (Österreich). Ber. Bayer. Bot. Ges. 57: 163-176. [available online at: http://www.bbgev.de/berichte/057_1986/galeobdolon_salzburg.pdf]