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Iris (plant)

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Iris is a genus of between 200-300 species of flowering plants with showy flowers which takes its name from the Greek word for a rainbow, referring to the wide variety of flower colours found among the many species. As well as being the scientific name, iris is also very widely used as a common name and refers to all Iris species as well as some closely related genera.

The genus is widely distributed throughout the north temperate zone. Their habitats are very varied, ranging from cold regions into the grassy slopes, meadowlands, stream banks and deserts of Europe, the Middle East and northern Africa, Asia and across North America.

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

The inflorescences are fan-shaped and contain one or more symmetrical, six-lobed, slightly fragrant flowers. These grow on a pedicel or lack a footstalk. The three sepals are spreading or droop downwards. They expand from their narrow base into a broader limb (= expanded portion), often 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, below).

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.

Contents

Cultivation

Irises are extensively grown as ornamental plants in gardens. The most commonly found garden iris is the bearded German Iris and its numerous cultivars. Various wild forms and naturally occurring hybrids of Iris pallida and I. variegata form the basis of most all modern hybrid bearded iris. Median forms of bearded iris [intermediate bearded (IB), miniature tall bearded (MTB), etc] are derived from crosses between tall and dwarf varieties. Other iris types commonly found in garden are I. siberica and its hybrids (Siberian irises) and I. ensata and its hybrids (Japanese irises).

The bearded irises are easy to cultivate and propagate, and have become very popular in gardens. They grow in any good free garden soil, the smaller and more delicate species needing only the aid of turf ingredients, either peat or loam, 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 'tall bearded' varieties, such as I. germanica, florentina, pallida, variegata, amoena, flavescens, sambucina, neglecta, ruthenica and their modern hybrids, produce their flowers.

The section Iris subgen. Iris sect. Oncocyclus contains the cushion or royal irises, a group of plants noted for their large, strongly 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 flowers are usually borne singly on the stalks. The closely allied Iris subgenus Iris sect. Regelia, includes several garden hybrids with species in sect. Oncocyclus, known as "Regelio-cyclus" irises. They are best planted in September or October in warm sunny positions, the rhizomes being lifted the following July after the leaves have withered.

Iris unguicularis (syn. I. stylosa) is a late winter flowering species from Algeria, with sky-blue flowers blotched with yellow, produced (in the Northern Hemisphere) from November to March or April.

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 covering of half-decayed leaves or fresh coco-fibre refuse. To this set belong I. milifolia, I. junonia, I. danfordiae, I. 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 naturally.

Uses

Chemical composition

Iris roots contain terpenes, organic acids (miristic acid, Undecilene acid, Tridecilic acid), glycosides iridin, and the leaves contain ascorbic acid.

Medicine and Healing

In ancient time the root of Iris use in parfumery and medicine. Today Iris essential oil (absolute) from flowers sometimes use in Aromatherapy as sedative medicines. The dried roots are also given whole to babies to help in teething.

Perfumery

Iris roots are harvested, dried, and aged for up to 5 years. In this time, the fats and oils inside the roots undergo degradation and oxidation, which produces many fragrant compounds that are invaluable in perfumery. The aged roots are steam distilled which produces a thick oily compound, known in the perfume industry as iris butter.

Art

The Artist George Gessert has specialised in breeding Irises.[link]

The Artist Vincent van Gogh has painted several famous pictures of irises. [link]

Image:Iris02.jpg|A purple bearded iris Image:Flagirissmall.jpg|The blue flag iris is the provincial flower of Quebec Image:Iris pallida.jpg|A modern hybrid bearded iris Image:Iris-versicolor.jpg|Blue Flag Iris (Iris versicolor) Image:Iris-lacustris.jpg|Dwarf Lake Iris (Iris lacustris) Image:Iris-japonica.jpg|Iris japonica from Curtis's Botanical Magazine 1797 Image:Koeh-211.jpg|Iris germanica Image:Koeh-078.jpg|Iris germanica var. florentina Image:Koeh-079.jpg|Iris pallida Image:Iris_Flower_hybr_Iridaceae_1-Luc_Viatour.jpg|Iris Hybr. Image:Iris_Flower_Hubr_iridaceae-2_Luc_Viatour.jpg|Iris Hybr.

Classification and taxonomy

Iris germanica
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Iris germanica

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.

There are six subgenera, of which five are restricted to the Old World, and the sixth (subgenus Limniris) with a Holarctic distribution; the two largest subgenera are further divided into sections.

Iris subgenus Iris
bearded irises, growing from rhizomes.
Iris subgenus Limniris
beardless irises, growing from rhizomes.
Iris subgenus Xiphium (syn. genus Xiphion), a group of bulbous irises.
Iris subgenus Nepalensis (syn. genus Junopsis); also bulbous.
Iris subgenus Scorpiris (syn. genus Juno); also bulbous.
Iris subgenus Hermodactyloides (syn. genus Iridodictyum); also bulbous.

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

References and external links

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