Iridaceae
Iridaceae only counts one native genus and species in Belgium, Iris pseudacorus L. (Lambinon & Verloove 2012). However, the family is represented in gardens by numerous taxa, several of which have escaped from cultivation. In this account five genera are included but most are not too well understood. Especially Crocus and Iris may count (many) more taxa than those recognized so far in the wild in Belgium. These genera surely require a more profound study.
In addition to the genera treated below many more are cultivated in Europe and might be recorded as garden escapes. Stace (2010) provides an extensive account and keys for subspontaneous Iridaceae in the British Isles. Walters & al. (1986) and Jäger & al. (2008) are very useful for the identification of cultivated members of Iridaceae in Europe.
1 Leaves with central whitish channel, linear. Flowers 1-few, directly arising from ground, Crocus-like === Crocus
Leaves wider, without central whitish channel, conspicuously flattened, with two identical faces (monofacial). Flowers several (rarely solitary), arising from aerial stems (these sometimes very short; if so, flowers never Crocus-like) === 2
2 Flowers zygomorphic === 3
Flowers radially symmetric === 4
3 Perianth segments brick-red to orange. Inflorescence a branched spike === Crocosmia
Perianth segments pinkish to purplish-red (variously colored in cultivars). Inflorescence usually unbranched === Gladiolus
4 Style branches broad and petaloid. Roots rhizomatous (or rarely bulbous). Perianth radially symmetric: 3 outer (lower) segments patent, recurved or reflexed, 3 inner (upper) segments erect, usually smaller and narrower. Perianth segments united at base, variably colored. Flowers always Iris-like === Iris
Style branches not broad or petaloid. Roots fibrous. Perianth radially symmetric: all segments alike. Perianth segments +/- free to base, bluish with yellow base or yellow. Flowers never Iris-like === Sisyrinchium
Literature:
There is a very extensive literature on the Iridaceae family. Only a small selection that appears to be relevant is provided here. Further useful information on the Iridaceae family is provided by ‘Iridaceae of the World’ at: http://iridaceae.e-monocot.org/.
Goldblatt P. (1990) Phylogeny and classification of Iridaceae. Ann. Missouri Bot. Gard. 77: 607-627.
Goldblatt P. (2002) Iridaceae. In: Flora of North America, vol. 26: 348-409. Oxford Univ. Press, New York. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10452]
Goldblatt P., Manning J.C. & Rudall P. (1998) Iridaceae. In: Kubitzki K. (ed.), The Families and Genera of Vascular Plants. 3: 295-333, Springer-Verlag, Berlin.
Goldblatt P., Rodriguez A., Powell M.P., Jonathan Davies T., Manning J.C., van der Bank M. & Savolainen V. (2008) Iridaceae ‘Out of Australasia’? Phylogeny, Biogeography, and Divergence Time Based on Plastid DNA Sequences. Systematic Botany 33(3): 495-508. [available online at: http://biology.mcgill.ca/faculty/davies/pdfs/Goldblatt%20et%20al.%202008.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.
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.
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Walters S.M., Brady A., Brickell C.D., Cullen J., Green P.S., Lewis J., Matthews V.A., Webb D.A., Yeo P.F. & Alexander J.C.M. (eds.) (1986) The European Garden Flora, vol. 1. Cambridge University Press: XV + 430 p.
Zhao Yutang, Noltie H.J. & Mathew B. (2000) Iridaceae. In: Wu Z.Y. & Raven P.H. (eds.), Flora of China, vol. 24. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 297-313. [available online at: http://flora.huh.harvard.edu/china/mss/volume24/IRIDACEAE.published.pdf]