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Iris (plant)
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Iris (plant)


Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Liliopsida
Order: Liliales
Genus: Iris

Iris is a genus of flowering plants with showy flowers ranging in colour from gold or yellow to white, blue, lavender and purple. Pink and apricot coloured irises have also been bred in some species. The name "Iris" can be applied either to the genus, or to any of the species within it. It is also applied to various subdivisions within the genus.

Table of contents
1 Description
2 Cultivation
3 Pollination
4 Taxonomic issues
5 Examples of Iris species
6 External links
7 References


There are many species of Iris, widely distributed throughout the north temperate zone. All Irises have long stems and six-lobed flowers with three petals sagging downwards (actually large sepals in the same colour as the flower), and three standing upright. Some smaller iris species have all six lobes pointing straight outwards. Typical irises grow from a creeping rhizome, but some species, known as bulbous irises, have a bulb.


The flag irises are for the most part of the easiest culture; they grow in any good free garden soil, the smaller and more delicate species only needing the aid of turfy ingredients, either peaty or loamy, to keep it light and open in texture. The earliest to bloom are the dwarf forms of Iris pumila, which blossom during March, April and May; and during the latter month and the following one most of the larger growing species, such as I. germanica, fiorenhina, pallida, variegata, amoena, flavescens, sambucina, neglecta, ruthenica, etc., produce their gorgeous flowers. Of many of the foregoing there are, besides the typical form, a considerable number of named garden varieties. Iris unguicularis (or stylosa) is a remarkable winter flowering species from Algeria, with sky-blue flowers blotched with yellow, produced (in the Northern Hemisphere) at irregular intervals from November to March, the bleakest period of the year.

Many other smaller species of bulbous iris, being liable to perish from excess of moisture, should have a well-drained bed of good but porous soil made up for them, in some sunny spot, and in winter should be protected by a 6-in, covering of half-decayed leaves or fresh coco-fibre refuse. To this set belong I. persica, reticulata, milifolia, junonia, danfordiae, reichenbachii and others which flower as early as February and March.

The cushion irises are somewhat fastidious growers, and to be successful with them they must be planted rather shallow in very gritty well-drained soil. They should not be disturbed in the., autumn, and after the leaves have withered the roots should be protected from heavy rains until growth starts again naturaily.

A white bearded iris and bulb


The iris flower is of special interest as an example of the relation between flowering plants and pollenating insects. The shape of the flower and the position of the pollen-receiving and stigmatic surfaces on the outer petals form a landing-stage for a flying insect which in probing the perianth for honey will first come in contact of perianth, three with the stigmatic stamens in one whorl surface which is borne and an ovary formed of three carpels. The shelf-like transverse projection on the inner whorl under side of the stamens, which is beneath the over-arching style arm below the stigma, so that the insect comes in contact with its pollen-covered surface only after passing the stigma, while in backing out of the flower it will come in contact only with the non-receptive lower face of the stigma. Thus an insect bearing pollen from one flower will in entering a second deposit the pollen on the stigma, while in backing out of a flower the pollen which it bears will not be rubbed off on the stigma of the same flower.

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.

The major subgenera widely recognised are:

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

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.

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.

Examples of Iris species

A blue flag iris, the provincial flower of Quebec

Includes material edited from a 1911 encyclopedia

External links