Gentiana L.
In its current circumscription Gentiana is a genus with 361 species (Mabberley 2008). It is obviously most diverse in China where 247 species occur, mostly in the mountainous southwestern part of the country (Ho & Pringle 1995). Molecular phylogenetic studies approve the segregation of related genera like Gentianella Moench and Gentianopsis Ma (e.g. Yuan & Kupfer 1995). In Belgium only two species are originally native: Gentiana cruciata L. and G. pneumonanthe L. (Lambinon & Verloove 2012). However, the genus is fairly popular in cultivation (at least 75 and possibly up to 100 species are found in cultivation) and some of these are susceptible to escape. Useful accounts for the genus in cultivation in Europe are provided by Cullen (2000) and Jäger & al. (2008). At least two species have been recorded more or less recently as probable escapes.
Additional information on Gentiana and related genera is provided by the Gentian Research Network at: http://gentian.rutgers.edu/index.htm.
1 Corolla yellow, with lobes much longer than tube. Stem robust, up to 150 cm tall. Leaves 80-150 mm wide, with 5-7 very distinct veins === Gentiana lutea
Corolla blue, with lobes not more than ½ as long as tube. Stem slender, rarely exceeding 60 cm. Leaves up to 40 mm wide, with indistinct veins === 2
2 Corolla 4-lobed (native) === G. cruciata
Corolla 5-lobed === 3
3 Leaves linear, with a single vein, usually less than 10 mm wide (native) === G. pneumonanthe
Leaves lanceolate, with 3-5 veins, up to 40 mm wide === G. asclepiadea
Additional alien: Gentiana acaulis L. (Eur., garden escape).
Literature:
Chen C.H. & Wang J.C. (1999) Revision of the genus Gentiana L. (Gentianaceae) in Taiwan. Bot. Bull. Acad. Sin. 40: 9-38. [available online at: http://ejournal.sinica.edu.tw/bbas/content/1999/1/bot41-02.pdf]
Cullen J. (2000) Gentiana. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 19-31.
Grisebach A.H.R. (1838) Genera et Species Gentianearum: viii+364 pp.
Halda J.J. (1995) Synopsis of the new system of the genus Gentiana. Acta Mus. Richnov. Sect. Nat. 3(1): 3-50.
Halda J.J. (1996) The genus Gentiana. Nové Město n. Metují.
Ho T.N. (1985) A study on the genus Gentiana of China (IV). Bull. Bot. Res. 5(4): 1-22.
Ho T.N. & Liu S.W. (1990) The infrageneric classification of Gentiana (Gentianaceae). Bull. Br. Mus. Nat. Hist. (Bot.) 20(2): 169-192.
Ho T.N. & Liu S.W. (2001) A worldwide monograph of Gentiana. Science Press, Beijing: 694 p.
Ho T.N., Liu S.W. & Lu X.F. (1996) A phylogenetic analysis of Gentiana (Gentianaceae). Acta Phytotax. Sin. 34(5): 505-530.
Ho T.N. & Pringle J.S. (1995) Gentianaceae. In: Wu Z.Y. & Raven P.H. (eds.), Flora of China, vol. 16: Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 1-139. [available online at: http://flora.huh.harvard.edu/china/PDF/PDF16/gentiana.pdf]
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.
Kelly J. (1992) Gentians. Garden (London)117: 465-469.
Köhlein F. (1986) Enziane und Glockenblumen. Stuttgart.
Lambinon J. & Verloove F. (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.
Marquand C.V.B. (1937) The gentians of China. Bulletin of Miscellaneous Information (Kew) 1937: 134-180.
Pringle J.S. (1978) Sectional and subgeneric names in Gentiana (Gentianaceae). Sida 7(3): 232-247.
Pritchard N.M. (1978) Gentians. J. Scott. Rock Gard. Club 16: 7-18.
Yuan Y.M. & Kupfer P. (1995) Molecular phylogenetics of the subtribe Gentianinae (Gentianaceae) inferred from the sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA. Plant Systematics and Evolution 196: 207-226.