Iris (plant)

See text.

Taxonomic issues

Up to 300 species have been placed in the genus Iris. Modern classifications, starting with W. R. Dykes' 1913 book, have subdivided them. Dykes referred to the major subgroupings as sections, but later authors have generally called them subgenera, while essentially retaining his groupings. Like some older sources, the influential classification by G. I. Rodionenko removed some groups (particularly the bulbous irises) to separate genera, but even if this is done the genus remains large and several subgenera, sections and/or subsections are recognised within it.

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The major subgenera widely recognised are:

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• Iris: bearded irises, growing from rhizomes.
• Limniris: beardless irises, growing from rhizomes.
• Xiphium, sometimes treated as genus Xiphion, the main group of bulbous irises.
• Nepalensis, sometimes treated as genus Junopsis; also bulbous.
• Scorpiris, sometimes treated as genus Juno; also bulbous.
• Hermodactyloides, sometimes treated as genus Iridodictyum, including the small Iris reticulata and some other similar species; also bulbous.

All modern authors regard the Snake's Head Iris as lying outside genus Iris, and classify it as Hermodactylus tuberosus.

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Among the lower level subgroupings usually recognised is Oncocyclus, a section or subsection within subgenus Iris, containing the cushion irises or Royal irises. These constitute a magnificent group of plants remarkable for their large, showy and beautifully marked flowers. Between 30 and 60 species are classified in this section, depending on the authority. Compared with other irises the cushion varieties are scantily furnished with narrow sickle shaped leaves and the blossoms are usually borne singly on the stalks. The best-known kinds are atrofusca, barnumae, bismarckiana, gatesi, heylandiana, iberica, haynei, mariae, meda, paradoxa, sari, sofarana and susiana; the last-named being popularly called the "mourning iris" owing to the dark silver appearance of its huge flowers.

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A closely allied group to the cushion irises are those known as Regelia, also within subgenus Iris, of which korolkowli, leichtlinii and vega are the best known. Some magnificent hybrids have been raised between these two groups, and a hardier and more easily grown race of garden irises has been produced under the name of regelio-cyclus. They are best planted in September or October in warm sunny positions, the rhizomes being lifted the following July after the leaves have withered.

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