Iris (plant)

From Academic Kids


A white iris
Scientific classification
L., 1753

See text.

Iris is a genus of flowering plants with showy flowers ranging in colour from gold, copper-red or yellow to white, blue, blue-violet, lavender, tan, maroon 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.
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A purple bearded iris
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White-purple-yellow Dutch iris


There are many species of Iris, widely distributed throughout the north temperate zone. Their habitats are very varied and range from cold regions into the grassy slopes, meadowlands, stream banks and deserts of Europe, the Middle East and northern Africa, Asia and southern North America. Elevation is of not much importance.

These are perennial herbs growing from creeping rhizomes (rhizomatous irises), or, in drier climates, from bulbs (bulbous irises). They have long, erect, flowering stems. These may be simple or branched, solid or hollow. These stalks may be flattened or have a circular transverse section. There are 3 - 10 basal, sword-shaped leaves growing in dense clumps.

The inflorescences are fan-shaped and contain 1 or more symmetrical, six-lobed, slightly fragrant flowers. These grow on a pedicel or lack a footstalk. The three sepals are spreading are sagging downwards. They expand from their narrow base into a broader limb (= expanded portion), adorned with lines or dots. The three, sometimes reduced, petals stand upright, partly behind the sepal bases. Some smaller iris species have all six lobes pointing straight outwards. The sepals and the petals differ from each other. They are united at their base into a floral tube, that lies above the ovary. The styles divide towards the apex into petaloid branches (see : pollination).


The flag irises are for the most part of the easiest culture and easily propagated. They have become very popular in the garden. 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 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 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 blue flag iris is the provincial flower of
A blue flag iris is the provincial flower of Quebec
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Sweet Iris (Iris pallida)
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Iris pallida in Montenegro
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Iris reichenbachii and Iris orienii
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Yellow Iris (Iris pseudacorus)


The iris flower is of special interest as an example of the relation between flowering plants and pollinating 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 nectar, 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:

  • 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.

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

  • The Douglas Iris, Iris douglasiana, is a common wildflower of the coasts of California and southern Oregon.
  • Iris florentina (often misspelled Iris fiorentina), with white or pale-blue flowers, is a native of the south of Europe. Modern authorities treat it as a subspecies, Iris germanica florentina, of I. germanica. It is the source of the violet-scented orris root used in perfumery. From the flowers of Iris florentina a pigment, the "verdelis," "vert d'iris," or iris-green, formerly used by miniature painters, was prepared by maceration, the fluid being left to putrefy, when chalk or alum was added.
  • Iris foetidissima, the Fetid Iris, gladdon or roastbeef plant, the Xyris or stinking gladdon of Gerard, is a native of England south of Durham and also of Ireland, southern Europe and North Africa. Its flowers are usually of a dull, leaden-blue colour; the capsules, which remain attached to the plant throughout the winter, are 2 to 3 in. long; and the seeds scarlet. When bruised this species emits a peculiar and disagreeable odour.
  • Iris germanica of central Europe, "the most common purple Fleur de Luce" of Ray, is the large common blue iris of gardens, the bearded iris or fleur de luce and probably the Illyrian iris of the ancients.
  • The beautiful Japanese Iris laevigator (Rabbitear Iris) is of comparatively modern introduction, and though of a distinct type h equally beautiful with the better-known species. The outer segmenu are rather spreading than deflexed, forming an almost circular flower which becomes quite so in some of the very remarkable duple varietics, in which six of these broad segments are produced instead of three. Of this too there are numberless varieties cultivated undei names. They require a sandy peat soil on a cool moist subsoil.
  • Iris orienii Orjen iris, a close relative to Iris pallida. An endemic alpine species with white flowers found in the karst mountain Orjen in Montenegro. It is very rare and protected.
  • Iris pallida Dalmatian iris, Sweet iris : native to the Illyrian coast (former Yugoslavia) but widley naturalized elsewhere. Iris pallida is cultivated for extraction of essential oils from its rhizome orris root. Prefers rocky places in the mediterranean and submediterranean zone and reaches sometimes montane regions at its southern range in Montenegro. Four varieties (regularly described as separate species) are recognised with one possible new alpine species having white flowers. The var´┐Ży with deep purplish flowers from Northern Italy and the Slovenian alps is called Iris cengialti.
  • Iris pseudacorus, the Yellow Flag or Yellow Iris, is common in Britain on river-banks, and in marshes and ditches. It is called the "water-flag" or "bastard floure de-luce" by John Gerard, who remarks that "although it be a water plant of nature, yet being planted in gardens it prospereth well." Its flowers appear in June and July, and are of a golden-yellow colour. The leaves are from 2 to 4 ft. long, and half an inch to an inch broad. Towards the latter part of the year they are eaten by cattle. The seeds are numerous and pale-brown; they have been recommended when roasted as a substitute for coffee, of which, however, they have not the properties. The astringent rhizome has diuretic, purgative and emetic properties, and may, it is said, be used for dyeing black, and in the place of galls for ink-making.
  • Iris reichenbachii Reichenbach iris is a small bearded alpine iris from the Balkan peninsula. Specimens from the west Balkans are much smaller than those from Greece and the eastern Balkans.
  • Iris reticulata and Iris persica, both of which are fragrant, are also great favourites with florists.
  • Iris versicolor, or Blue Flag, is indigenous to North America, and yields "iridin," a powerful hepatic stimulant.
  • Iris xiphium, the Spanish Iris and
  • Iris xiphioides, the English Iris. Despite the common name of I xiphioides, both are of Spanish origin, and have very showy flowers, so they are popular with gardeners and florists. They are among the hardier bulbous irises, and can be grown in northern Europe. They require to be planted in thoroughly drained beds in very light open soil, moderately enriched, and should have a rather sheltered position. Both these present a long series of beautiful varieties of the most diverse colours, flowering in May, June and July, the smaller Spanish iris being the earlier of the two.


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Iris japonica
from Curtis's Botanical Magazine 1797

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