Tulipa is a moderately large genus of ca. 76 species (much less than previously assumed; Christenhusz & al. 2013). Its center of diversity is in western Asia. It is furthermore well represented in Eurasia and northern Africa. Not a single species is native in Belgium. However, the genus is extremely popular in horticulture and numerous species, cultivars and hybrids are grown as ornamentals. Useful accounts for Tulipa in cultivation in Europe are provided by Matthews & Grey-Wilson (1986) and Jäger & al. (2008).
A recent molecular study shed new light on the genus Tulipa (Christenhusz & al. 2013). Key results were:
• The genus is strongly supported as monophyletic and four clearly defined clades (subgenera) are discernible;
• The genus counts ca. 76 species;
• A revised checklist with full synonymy, typification and distribution is provided;
• The status of T. ×gesneriana and its synonyms is discussed;
• All accepted species are classified into the four subgenera supported by the phylogenetic study.
Tulipa in the wild in Belgium is still very poorly studied. In addition to the two taxa treated in detail in this account, at least a third one has been observed but its identity is uncertain. It was tentatively named Tulipa tarda Stapf (see photo), a species that is better included in T. urumiensis Stapf according to Christenhusz & al. (2013), contrary to Zonneveld (2009).
1 Flowers rounded at base. Tepals variously colored (red, yellow, pink, purple, white). Filaments glabrous. Buds erect === Tulipa xgesneriana
Flowers cuneate at base. Tepals yellow. Filaments pubescent near base. Buds pendent === T. sylvestris
Botschantzeva Z.P. (1982) Tulips: taxonomy, morphology, cytology, phytogeography and physiology (translated and edited by H.Q. Varekamp). Balkema, Rotterdam: 230 p.
Christenhusz M.J.M., Govaerts R., David J.C., Hall T., Borland K., Roberts P.S., Tuomisto A., Buerki S., Chase M.W. & Fay M.F. (2013) Tiptoe through the tulips – cultural history, molecular phylogenetics and classification of Tulipa (Liliaceae). Botanical Journal of the Linnean Society 172(3): https://www.researchgate.net/publication/262873497_Tiptoe_through_the_tu...
Hall A.D. (1940) The Genus Tulipa: VIII + 171 p. + 40 plates.
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.
Matthews V.A. & Grey-Wilson C. (1986) Tulipa. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1. Cambridge University Press, Cambridge: 179-187.
Pavord A. (1999) The tulip. New York, London, Bloomsbury: 296 p.
Raamsdonk L.W.D. von & De Vries T. (1996) Cultivar classification in Tulipa L. (Liliaceae). Acta Bot. Neerl. 45: 183-198.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Stork A.L. (1985) Tulipes sauvages et cultivées. Série documentaire des Conservatoire et Jardin botaniques 13: 1-185.
Zonneveld B.J.M. (2009) The systematic value of nuclear genome size for ‘all’ species of Tulipa L. Plant Systematics and Evolution 281: 217–245. [available online at: https://www.researchgate.net/publication/226826194_The_systematic_value_...