| Blood Iris (Iris sanguinea),|
known as ayame in Japan
| Iris germanica|
Iris is a genus of 260 species of flowering plants with showy flowers. It takes its name from the Greek word for a rainbow, referring to the wide variety of flower colors found among the many species. As well as being the scientific name, iris is also very widely used as a common name for all Iris species, though some plants called thus belong to other closely related genera. A common name for some species is 'flags', while the plants of the subgenus Scorpiris are widely known as 'junos', particularly in horticulture. It is a popular garden flower.
The genus is widely distributed throughout the north temperate zone. Their habitats are considerably varied, ranging from cold and montane regions to the grassy slopes, meadowlands and riverbanks of Europe, the Middle East and northern Africa, Asia and across North America.
Irises 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 flowers. These grow on a pedicel or lack a footstalk. The three sepals, which are spreading or droop downwards, are referred to as "falls". They expand from their narrow base, which in some of the rhizomatous irises has a "beard" (a tuft of short upright extensions growing in its midline), into a broader expanded portion ("limb"), often adorned with veining, lines or dots. The three, sometimes reduced, petals stand upright, partly behind the sepal bases. They are called "standards". Some smaller iris species have all six lobes pointing straight outwards, but generally, limb and standards differ markedly in appearance. They are united at their base into a floral tube that lies above the ovary (known as an inferior ovary). The styles divide towards the apex into petaloid branches; this is significant in pollination.
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, then with the stigmatic stamens in one whorled surface which is borne on an ovary formed of three carpels. The shelf-like transverse projection on the inner whorled underside of the stamens 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; 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; in backing out of a flower, the pollen which it bears will not be rubbed off on the stigma of the same flower.
Systematics and taxonomyEdit
Up to 300 species – many of them natural hybrids – 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.
In general, modern classifications usually recognise six subgenera, of which five are restricted to the Old World; the sixth (subgenus Limniris) has a Holarctic distribution. The two largest subgenera are further divided into sections.
Bearded rhizomatous irises
Beardless rhizomatous irises
- Iris confusa – Bamboo Iris
- Iris cristata – Crested Iris
- Iris gracilipes A.Gray
- Iris japonica Thunb.
- Iris lacustris – Dwarf Lake Iris
- Iris milesii Foster
- Iris tectorum Maxim. – Wall Iris
- Iris tenuis S.Wats. – Clackamas Iris
- Iris wattii Baker ex Hook.f.
Smooth-bulbed bulbous irises. Formerly genus Xiphion. Section Xiphium
- Iris boissieri Henriq
- Iris filifolia Boiss.
- Iris juncea Poir.
- Iris latifolia – English Iris
- Iris serotina Willk. in Willk. & Lange
- Iris tingitana Boiss. & Reut. – Morocco Iris
- Iris xiphium – Spanish Iris, Dutch Iris, Small Bulbous-rooted Iris
Bulbous irises. Formerly genus Junopsis.
Smooth-bulbed bulbous irises known as "junos". Formerly genus Juno.
Reticulate-bulbed bulbous irises. Formerly genus Iridodictyum.
- Iris bakeriana Foster
- Iris danfordiae (Baker) Boiss.
- Iris histrio Rchb.f.
- Iris histrioides (G.F.Wilson) S.Arn.
- Iris kolpakowskiana Regel
- Iris pamphylica Hedge
- Iris reticulata Bieb.
- Iris vartanii Fost.
- Iris winogradowii Fomin
Irises are extensively grown as ornamental plants in home and botanical gardens. Presby Memorial Iris Gardens in New Jersey, for example, is a living iris museum with over 10,000 plants, while in Europe the most famous iris garden is arguably the Giardino dell'Iris in Florence (Italy) which every year hosts one of the most famous iris breeders' competitions in the world.
The most commonly found garden iris is the bearded German Iris (I. germanica), a hybridogenic species, and its numerous cultivars. Various wild forms and naturally occurring hybrids of the Sweet Iris (I. pallida) and the Hungarian Iris (I. variegata) form the basis of most all modern hybrid bearded irises. Median forms of bearded iris (intermediate bearded, or IB; miniature tall bearded, or MTB; etc.) are derived from crosses between tall and dwarf varieties.
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 species like I. junonia and I. reichenbachii, which flower as early as February and March, followed by the dwarf forms of I. pumila which blossom during March, April and May. During the latter month and the following one, most of the larger-growing "tall bearded" irises bloom, such as the German Iris and its variety florentina, Sweet Iris, Hungarian Iris, Lemon-yellow Iris (I. flavescens), Iris sambucina, I. amoena, and their natural and horticultural hybrids such as those described under names like I. neglecta or I. squalens and best united unter I. × lurida.
The section Oncocyclus contains the cushion irises 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; they are often very dark and in some almost blackish. 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.
The section Regelia, closely allied to the cushion irises, includes several garden hybrids with species in section 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.
A truly red bearded iris remains an unattained goal despite frequent hybridizing and selection. There are species and selections, most notably based on the beardless rhizomatous Copper Iris (I. fulva), which have a relatively pure red color. However, getting this color into a modern bearded iris breed has proven very difficult, and thus, the vast majority of irises are in the purple and blue range of the color spectrum, with yellow and whitish breeds also quite frequent.
Other beardless rhizomatous iris types commonly found in garden are the Siberian Iris (I. sibirica) and its hybrids, and the Japanese Iris (I. ensata) and its hybrids. "Japanese Iris" is also a catch-all term for the Japanese Iris proper (hanashōbu), the Blood Iris (I. sanguinea, ayame) and the Rabbitear Iris (I. laevigata, kakitsubata). I. unguicularis 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. Yet another beardless rhizomatous iris popular in gardening is I. ruthenica, which has much the same requirements and characteristics as the "tall bearded" irises.
Many of the 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 cocos-fibre refuse. To this group belong the "reticulate" irises with their characteristic bulbs, including I. danfordiae, I. histrioides, I. reticulata and others, as well as the smmoth-bulbed I. filifolia, which flower as early as February and March
Rhizomes of the German Iris (I. germanica) and Sweet Iris (I. pallida) are traded as orris root and are used in perfume and medicine, though more common in ancient times than today. Today Iris essential oil (absolute) from flowers are sometimes used in aromatherapy as sedative medicines. The dried rhizomes are also given whole to babies to help in teething. Gin brands such as Bombay Sapphire and Magellan Gin use orris root and sometimes iris flowers for flavor and color.
For orris root production, iris rhizomes 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 valuable in perfumery. The scent is said to be similar to violets. The aged rhizomes are steam-distilled which produces a thick oily compound, known in the perfume industry as "iris butter".
Iris rhizomes also contain notable amounts of terpenes, and organic acids such as ascorbic acid, myristic acid, tridecylenic acid and undecylenic acid. Iris rhizomes can be toxic. Larger Blue Flag (I. versicolor) and other species often grown in gardens and widely hybridized contain elevated amounts of the toxic glycoside iridin. These rhizomes can cause nausea, vomiting, diarrhea, and/or skin irritation, but poisonings are not normally fatal. Irises should only be used medicinally under professional guidance.
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