Potentilla inclinata Vill. (syn.: P. canescens Besser) (C, E and S-Eur.) – A very rare, locally naturalized alien. Already documented from Belgium (without further details) in the first half of the 19th century. Recorded around 1894 on old walls in Leuven and since then regularly collected from widely scattered localities, apparently mostly as an ephemeral alien. However, Potentilla inclinata is by far best known from the Borinage area where it is firmly established since many decades (at least since 1954 when it was found in Quaregnon-Rivage) on coal mining spoil heaps, by abandoned railway tracks and similar sunny habitats on gravelly substratum. In this area it is known at present from Hornu, Mons, Quaregnon, Saint-Ghislain, etc. In 1987 also seen on a canal bank in Sint-Job-in-‘t-Goor (canal Dessel-Turnhout-Schoten) and in 2011 also observed in relative abundance on a sun-exposed slope of a clay pit in Egem. Other claims require confirmation; most are probably erroneous and referable to Potentilla intermedia.
Potentilla inclinata is traditionally placed in sect. Argenteae (Wolf 1908) but is morphologically obviously closer to sect. Rivales which includes P. intermedia and allies (especially P. heidenreichii Zimm.). Recent cladistic analysis confirmed this relationship (Leht & Paal 1998). It is a very variable, apomictic species and, in general appearance, is intermediate between Potentilla argentea L. and P. recta L. According to some authors it is an established hybrid between these species (Kurtto & al. 2004).
P. inclinata is widely confused with P. intermedia (Leht & Paal 1998, Soják 2009). Siberian records are all referable to the latter or hybrids of P. argentea (Soják l.c.). Both are best distinguished on measurements of floral parts (petals, anthers; see key and Soják 1995). Leaf indumentum appears to be exceedingly variable in this section, especially in Potentilla intermedia. Achene characters (smooth vs. rugose; cf. Stace 2010) have no diagnostic value for the separation of P. inclinata and P. intermedia.
Some authors have proposed to use the (younger) name Potentilla canescens Besser for this species, P. inclinata being a confusing name that has widely been misapplied (Kurtto & al. 2004). A conservation proposal for P. inclinata was recently addressed by Gregor & al. (2009), against the earlier name P. assurgens Vill. (the latter moreover being an invalid name according to Kurtto & al. l.c.).
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Selected literature:
Ertter B., Elven R., Reveal J.L. & Murray D.F. (2014) Potentilla. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 9. Oxford University Press, New York-Oxford: 121-218. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=126635]
Gregor T., Poncet V. & Tison J.-M. (2009) (1891) Proposal to conserve the name Potentilla inclinata against P. assurgens (Rosaceae). Taxon 58(2): 651-652. [available online at: http://flora-deutschlands.de/Publikationen/2009_taxon_potentilla_inclinata.pdf]
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.
Leht M. (1994) Hankalia hanhikkeja (Troublesome cinquefoils). Lutukka 10(3): 72-76.
Leht M. (1997) Distribution and nomenclature problems of the Baltic taxa of the genus Potentilla L. Botanica Lithuanica, Suppl. 1: 15-27.
Leht M. & Paal J. (1998) Potentilla L. sect.Rivales Wolf and related taxa in the Baltic states. Folia Geobotanica 33(2): 171-186.
Pütz N. (2006) Seedling establishment, underground kinetics, and clonal reiteration: How do Potentilla inclinata and Inula ensifolia get their multifunctional subterranean system? Flora 201: 298-306. [available online at: http://www.uni-vechta.de/fileadmin/user_upload/news/Biologie/Mitarbeiter_innen/Puetz__Norbert/Publikationen/2006-Flora_seedling_establishment_Potentilla_Inula.pdf]
Soják J. (1995) Potentilla. In: Slavík B. (ed.), Kvĕtena České Republiky, vol. 4. Academia, Praha: 283-314.
Soják J. (2009) Potentilla L. (Rosaceae) in the former USSR; second part: comments. Notes on Potentilla XXIV. Feddes Repert. 120(3-4): 185-217.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Wolf T. (1908) Monographie der Gattung Potentilla L. Bibl. Bot. 71: 1-714.
Wollert H. (2002) Zum soziologischen Verhalten von Potentilla inclinata auf dem Silberg bei Teschow (Ostmecklenburg). Botanischer Rundbrief für Mecklenburg-Vorpommern 36: 39-43.