Iris L.

Iris is a taxonomically difficult genus of ca. 280 species, primarily distributed in the northern hemisphere (Mabberley 2008). Its generic limits are controversial and recent molecular data seem to favor a much narrower circumscription. According to Mavrodiev & al. (2014) Iris should be divided in at least 23 segregate genera. Pending additional studies a conservative taxonomy is here applied. A single species is native in Belgium, Iris pseudacorus L. (Lambinon & Verloove 2012), but many more are cultivated as ornamentals in gardens. Garden-plants are often complex artificial hybrids and their identification is rarely straightforward. Several other taxa, in addition to the species treated below, possibly occur in the wild in Belgium (especially species from the Iris germanica-group, although their taxonomic value may be questionable; see for instance Adolphi 1995).

A very useful account for the genus Iris in Germany, in the wild as well as cultivated, is provided by Stolley at: and by Meyer at:

1       Leaves channeled, not flattened. Plants with a bulb. Flowers few, usually 1-3, yellow with white standards === Iris xhollandica

         Leaves distinctly flattened. Plants rhizomatous, never with bulbs. Flowers usually more numerous, variably colored === 2

2       Outer tepals bearded (i.e., with many multicellular hairs on inner surface) === 3

         Outer tepals not bearded === 4

3       Stem 30-100 cm, branched. Inflorescence usually exceeding leaves, 2-4-flowered. Floral tube 1-2,5 cm long === I. germanica

         Stem absent or very short, unbranched. Inflorescence exceeded by leaves, 1-flowered. Floral tube 6-10 cm long === I. pumila

4       Leaves dark green, persisting in winter and with unpleasant smell when crushed. Seeds scarlet or bright orange === I. foetidissima

         Leaves paler, dying in winter and with indistinct smell when crushed. Seeds brown === 5

5       Tepals predominantly yellow(-ish). Leaves 10-30 mm wide. Stem solid (native) === I. pseudacorus

         Tepals predominantly blue or bluish-violet. Leaves 4-10 mm wide. Stem hollow === I. sibirica

Additional alien: Iris graminea L. (Euras., garden escape).


There is a vast literature on the genus Iris. Only some of the more relevant references are cited here.

Additional useful information is available, for instance, here:

Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 1-272.

Dykes W.R. (1913) The Genus Iris: III + 245 pp.

Henderson N.C. (2002) Iris. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 26. Oxford University Press, New York-Oxford: 371-395. [available online at:]

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.

Koehlein F. (1981) Iris. 360 pp. + 147 photographs.

Koehlein F. (1987) Iris. 370 pp.

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.

Mathew B. (1990) The Iris (rev. ed.). Timber Press, Portland & Oregon: 202 p.

Matthews V.A. & Mathew B. (1986) Iris. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1. Cambridge University Press, Cambridge: 334-354.

Mavrodiev E.V., Martínez-Azorín M., Dranishnikov P. & Crespo M.B. (2014) At Least 23 Genera Instead of One: The Case of Iris L. s.l. (Iridaceae). PLoS ONE 9(8): e106459. doi:10.1371/journal.pone.0106459. [available online at:]

Reeves G., Chase M.W., Goldblatt P., Rudall P., Fay M.F., Cox A.V., Lejeune B. & Souza-Chies T. (2001) Molecular systematics of Iridaceae: evidence from four plastid DNA regions. Amer. J. Bot. 88: 2074-2087. [available online at:]

Species group of the British  Society (1997) A guide to species Iris. Their identification and cultivation. Species group of the British Society: 171 pp.

Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.

Webb D.A. & Chater A.O. (1978) Flora europaea. Notulae systematicae no. 20. Notes on the genus Iris L. Bot. J. Linn. Soc. 76: 315-316.

Werckmeister P. (1967) Catalogus Iridis 1967. Namen und Synonyme des Genus Iris., Deutsche Iris - Lilienges. Jahrb. 1967: 1-160.

Williams C.A., Harborne J.B. & Colasante M. (1997) Flavonoid and xanthone patterns in bearded Iris species and the pathway of chemical evolution in the genus. Biochem. Syst. & Ecol. 25(4): 309-325.

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:]

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith