Iris (plant)

Description

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.

Cultivation

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

A purple bearded iris

Pollination

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:

• 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

Yellow Iris (Iris pseudacorus)

• 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 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.
• 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 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.
• I. reticulata and I. persica, both of which are fragrant, are also great favourites with florists.
• The beautiful Japanese I. 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.
• The Douglas Iris, I. douglasiana, is a common wildflower of the coasts of California and southern Oregon.

A blue flag iris, the provincial flower of Quebec

Includes material edited from a 1911 encyclopedia

External links

• A web site devoted to Irises (http://aleph0.clarku.edu/~djoyce/iris/index.html), by David Payne-Joyce; includes plates from Dykes (1913).
• The American Iris Society (http://www.irises.org/)
• Treatment of Irises in the online Flora of North America (http://flora.huh.harvard.edu:8080/flora/browse.do?flora_id=1&taxon_id=116503&key_no=1)

References

• Dykes, W. R. (1913). The genus Iris. Cambridge: Cambridge University Press.
• Rodionenko, G. I. (1961). The genus Iris L.. Moscow and Leningrad.

bg:Ирис (цвете) de:Schwertlilien fr:Iris (fleur) it:Iris (botanica) nl:Iris (plant) ja:カキツバタ zh:鸢尾花