Geum L.
(incl. Waldsteinia Willd.)
The generic boundaries of Geum have long been controversial. Many segregates have been described and this narrow generic concept is still adopted by some recent taxonomists (see for instance Mabberley 2008). However, recent molecular phylogenetic studies (e.g. Potter & al. 2007) include most of these segregates in Geum. Waldsteinia is nested in Geum as well (Smedmark 2006) and therefore also preferably included in a broadly circumscribed genus Geum (see, however, Rohrer 2014). The number of species in Geum s.l. is quite uncertain and ranges from about 40 to 70. It is mostly confined to the cooler and temperate regions of the northern hemisphere but some species occur in South America as well. Two species are native in Belgium: Geum rivale L. and G. urbanum L. (Lambinon & Verloove 2012). In regions where they occur sympatrically their hybrid (Geum xintermedium Ehrh.) is not rare.
Several species and complex hybrids and cultivars of Geum are cultivated as ornamentals (e.g. Knees 1995, Rae 1995, Jäger & al. 2008). The exact identity of some of these (especially those related to the red-flowered Geum coccineum Sibth. et Sm. and/or G. quellon Sweet) is critical (see also Jäger & al. 2008). Most other species of Geum also freely hybridize and their hybrids are often (partly) fertile.
1 Stem creeping, stoloniferous. All leaves ternate === Geum ternatum
Stem erect, without stolons. At least basal leaves pinnate === 2
2 Petals pinkish, purplish or reddish === 3
Petals yellow === 4
3 Flowers nodding. Carpophore distinct, 5-10 mm long. Petals pinkish (native) === G. rivale
Flowers erect. Carpophore absent. Petals reddish (scarlet) === G. quellyon
4 Basal part of style minutely glandular. Achenes ca. 200 or more per head. Terminal leaflet of basal leaves always very large, cordate at base and usually at least as wide as long === G. macrophyllum
Basal part of style eglandular. Achenes ca. 120-140 per head, rarely less. Terminal leaflet of basal leaves very variable, either cuneate to cordate at base (native) === G. urbanum
Additional alien: Geum laciniatum Murray was cited by Lambinon & al. (2004) but is has never been reliably collected in Belgium (Verloove & Lambinon 2006).
Literature:
Bolle F. (1933) Eine Übersicht über die Gattung Geum L. und die ihr nahestehenden Gattungen. Feddes Repert., Beiheft 72: 1-119.
Gajewski W. (1955) Cytogenetic relations of Geum macrophyllum Willd. with G. perincisum Rydb. and G. oregonense Rydb. Acta Soc. Bot. Polon. 24: 311-334.
Gajewski W. (1957) A cytogenetic study of Geum L. Monogr. Bot. 4: 1-407.
Gajewski W. (1959) Evolution in the genus Geum. Evolution 13: 378-388.
Gajewski W. (1968) Geum. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 2. Cambridge University Press, Cambridge: 34-36.
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.
Knees S.G. (1995) Waldsteinia. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 4. Cambridge University Press, Cambridge: 390-391.
Kowal T. & Krupinska A. (1969) Cechy diagnostyczne owoców i nasion rodzaju Geum L. (The diagnostic characters of fruits and seeds of Geum L. species). Monogr. Bot. 29: 69-120.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H.) (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 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.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Potter D., Eriksson T., Evans R.C., Oh S., Smedmark J.E.E., Morgan D.R., Kerr M., Robertson K.R., Arsenault M., Dickinson T.A. & Campbell C.S. (2007) Phylogeny and classification of Rosaceae. Pl. Syst. Evol. 266: 5-43.
Rae D.A.H. (1995) Geum. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 4. Cambridge University Press, Cambridge: 389-390.
Rohrer J.R. (2014) Geum. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 9. Oxford University Press, New York-Oxford: 58-70. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=113505]
Smedmark J.E.E. (2004) The evolutionary history of Geum (Rosaceae, Colurieae): a study of ancient allopolyploid speciation. Doctoral thesis.
Smedmark J.E.E. (2006) Recircumscription of Geum (Colurieae: Rosaceae). Bot. Jahrb. Syst. 126(4): 409-417.
Smedmark J.E.E. & Eriksson T. (2002) Phylogenetic relationships of Geum (Rosaceae) and relatives inferred from the nrITS and trnL-trnF regions. Syst. Bot. 27(2): 303-317. [available online at: http://www.bergianska.se/polopoly_fs/1.67634.1324555525!/menu/standard/file/Smedmark_Eriksson_2002_1.pdf]
Teppner H. (1968) Zur Kenntnis der Gattung Waldsteinia. Diss. Phil. Graz.: II + 129 p.
Verloove F. & Lambinon J. (2006) The non-native vascular flora of Belgium: a new nothospecies and three new combinations. Syst. Geogr. Pl. 76: 217-220.