Geum macrophyllum Willd. (N-Am., E-As.) – A rare but recently much increasing, locally naturalized escape from cultivation. Probably first recorded in Oud-Heverlee (Meerdaalwoud) in 1994 (Meerts 1995, Havrenne 1996) and well-established there (Verloove 2002). Subsequently also recorded in Vijvergebied Midden-Limburg (Verloove 2006). Since then discovered in several additional localities, for instance in the surroundings of Brugge (often in more or less natural or remote areas, e.g. in Bulskampveld near Wingene or Rijkevelde near Sijsele) and in the Kempen. An up-to-date overview of Belgian records is available here: http://waarnemingen.be/soort/view/9186. Similar records and trends have been reported from the Netherlands as well (see for instance van der Ploeg 1999, Bax 2000, Holverda & al. 2009, etc.).
Geum macrophyllum usually grows in more or less similar conditions as native G. urbanum: rather damp and nitrophilous, usually shady habitats (deciduous woodland, along tracks or road verges in woodland, etc.).
Geum macrophyllum is possibly overlooked. It strongly reminds of forms of native G. urbanum with basal leaves with large terminal leaflet with cordate base. Such plants are only reliably separated from Geum macrophyllum by their eglandular style base and the lower number of achenes per head. More or less intermediate plants with strongly reduced fertility may belong to Geum xconvallis Wilcox (Wilcox 2015; see also Smejkal 1959) and should be looked for where both parental species grow.
Geum macrophyllum has also been confused with G. japonicum Thunb., especially in horticulture. The latter has been reliably (?) recorded from Germany (Kuhbier 1991, Weber 1995, Jäger & Werner 2005; see, however, Smejkal 1959, Kurtto & al. 2004) and records of Geum macrophyllum should therefore be critically assessed. Both species have a glandular style base. According to Hara (1952) they are best distinguished as follows: Geum japonicum has smaller, ovate-lanceolate entire stipules (less than 10 mm long), more coarsely hairy peduncles and a more densely and longer hairy receptacle.
 |
 |
 |
 |
Selected literature:
Bax G.M. (2000) Geum macrophyllum Willd. op verschillende plaatsen en al lange tijd in Nederland. Gorteria 26: 19.
Hara H. (1952) Contributions to the study of variations in the Japanese plants closely related to those of Europe or North America. Part 1. Journ. Fac. Sci. Univ. Tokyo, III 6(2): 29-96.
Havrenne A. (1996) A propos de la trouvaille de Geum macrophyllum en forêt de Meerdaal. Dumortiera 63: 31-32.
Holverda W., van Moorsel R. & Duistermaat L. (2009) Nieuwe vondsten van zeldzame planten in 2005, 2006 en ten dele 2007. Gorteria 34: 1-40.
Jäger E.J. & Werner K. (eds.) (2005) Rothmaler Band 4. Exkursionsflora von Deutschland. Gefässpflanzen: Kritischer Band. Springer Verlag, Berlin: 880 p.
Kuhbier H. (1991) Die Japanische Nelkenwurz (Geum japonicum Thunberg) im Bürgenpark, eine Neubürgerin der Bremer Flora. Jb. Wittheit Bremen 32: 358-361.
Kurtto A., Lampinen R. & Junikka L. (eds.) (2004) Atlas Florae Europaeae. 13. Rosaceae (Spiraea to Fragaria, excl. Rubus). The Committee for Mapping the Flora of Europe & Societas Biologica Fennica Vanamo, Helsinki: 320 p.
Meerts P. (1995) Geum macrophyllum Willd., nouveau pour la Belgique, en forêt de Meerdaal. Dumortiera 61-62: 74-76.
Smejkal M. (1959) Geum macrophyllum x urbanum (G. x gajewskii nom. nov.) jako spontánní bastard v Československu. Preslia 31: 8-13.
Van der Ploeg D.T.E. (1999) Geum macrophyllum Willd. ook in Nederland. Gorteria 25: 17-19.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Geum macrophyllum. 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: 440.
Vinogradova Y.K. (2008) Biological features and competitive relations of alien and native species of the Genus Geum L. Russian Journal of Biological Invasions 2: 2-8. [available online at: http://www.sevin.ru/invasjour/issues/2008_2/Vinogradova_08_2.pdf]
Weber H.E. (1995) Rosoideae. In: Hegi G.B. (ed.), Illustrierte Flora von Mitteleuropa, 4 (2A), p. 269-659. Blackwell Wissenschafts-Verlag, Berlin.
Wilcox M.P. (2015) Geum x convallis (G. macrophyllum x G. urbanum, Rosaceae): a new Geum hybrid from England. New Journ. Bot. 5(1): 26-31.