Iris is a genus of about 260-300, species of flowering plants with showy flowers. It takes its name from the Greek word for a rainbow, which is also the name for the Greek goddess of the rainbow, Iris. Some authors state that the name refers 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, as well as some belonging 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 often-segregated, monotypic genera Belamcanda (blackberry lily, I. domestica), Hermodactylus (snake's head iris, I. tuberosa), and Pardanthopsis (vesper iris, I. dichotoma) are currently included in Iris.
Three Iris varieties are used in the Iris flower data set outlined by Ronald Fisher in his 1936 paper The use of multiple measurements in taxonomic problems as an example of linear discriminant analysis.
Iris is the national flower of Croatia.
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Description
Irises are perennial plants, 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.
Flower
The inflorescences are in the shape of a fan and contain one or more symmetrical six-lobed flowers. These grow on a pedicel or peduncle. The three sepals, which are usually spreading or droop downwards, are referred to as "falls". They expand from their narrow base (the "claw" or "haft" ), into a broader expanded portion ("limb" or "blade") and can be adorned with veining, lines or dots. In the centre of the blade, some of the rhizomatous irises have a "beard" (a tuft of short upright extensions growing in its midline),. which are the plants filaments.
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 epigynous or inferior ovary). The styles divide towards the apex into petaloid branches; this is significant in pollination.
The iris flower is of 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 for nectar, will first come into contact with the 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 overarching 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.
The iris fruit is a capsule which opens up in three parts to reveal the numerous seeds within. In some species, the seeds bear an aril.
Flags Flowers Video
Taxonomy
Iris is the largest genus of the family Iridaceae with up to 300 species - many of them natural hybrids. Modern classifications, starting with Dykes (1913), have subdivided them. Dykes referred to the major subgroupings as sections. Subsequent authors such as Lawrence (1953) and Rodionenko (1987) have generally called them subgenera, while essentially retaining Dykes' groupings, using six subgenera further divided into twelve sections. Of these, section Limneris (subgenus Limneris) was further divided into sixteen series. Like some older sources, Rodionenko moved some of the bulbous subgenera (Xiphium, Scorpiris and Hermodactyloides) into separate genera (Xiphion, Juno and Iridodictyum respectively), but this has not been accepted by later writers such as Mathew (1989), although the latter kept Hermodactylus as a distinct genus, to include Hermodactylus tuberosus, now returned to Hermodactyloides as Iris tuberosa.
Rodionenko also reduced the number of sections in subgenus Iris, from six to two, depending on the presence (Hexapogon) or absence (Iris) of arils on the seeds, referred to as arilate or nonarilate. Taylor (1976) provides arguments for not including all arilate species in Hexapogon.
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.
Subgeneric division
Subgenera
- Iris (Bearded rhizomatous irises)
- Limniris (Beardless rhizomatous irises)
- Xiphium (Smooth-bulbed bulbous irises: Formerly genus Xiphion)
- Nepalensis (Bulbous irises: Formerly genus Junopsis)
- Scorpiris (Smooth-bulbed bulbous irises: Formerly genus Juno)
- Hermodactyloides (Reticulate-bulbed bulbous irises: Formerly genus Iridodictyum)
Sections, series and species
Distribution and habitat
Nearly all species are found in temperate Northern hemisphere zones, from Europe to Asia and across North America. Although diverse in ecology, Iris is predominantly found in dry, semi-desert, or colder rocky mountainous areas, other habitats include grassy slopes, meadowlands, bogs and riverbanks.
Cultivation
Iris is extensively grown as ornamental plant 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 a well attended iris breeders' competition. Irises, especially the multitude of bearded types, feature regularly in shows such as the Chelsea Flower Show.
For garden cultivation, iris classification differs from taxonomic classification. Garden iris are classed as either bulb iris or rhizome iris (called rhizomatous) with a number of further subdivisions. Due to a wide variety of geographic origins, and thus great genetic diversity, cultivation needs of iris vary greatly.
Iris grow well in most any garden soil types providing they are well-drained. The earliest to bloom are species like I. junonia and I. reichenbachii, which flower as early as February and March in the Northern Hemisphere, followed by the dwarf forms of I. pumila, and then by most of the tall bearded varieties, 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 under I. × lurida.
Bearded Rhizome Iris
Bearded iris are classified as Dwarf, Tall, or Aril. In Europe, the most commonly found garden iris is a hybrid iris (falsely called German Iris, I. germanica which is sterile) and its numerous cultivars. Various wild forms (including Iris aphylla) and naturally occurring hybrids of the Sweet iris (I. pallida) and the Hungarian iris (I. variegata) form the basis of almost 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 species like Iris pumila.
The bearded irises are easy to cultivate and propagate and have become very popular in gardens. A small selection is usually held by garden centres at appropriate times during the season, but there are thousands of cultivars available from specialist suppliers (more than 30 000 cultivars only for the tall bearded irises !). They are best planted as bare root plants in late summer, in a sunny open position with the rhizome visible on the surface of the soil and facing the sun. They should be divided in summer every two or three years, when the clumps become congested.
A truly red bearded iris, like a truly blue rose, 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, pink, orange and white breeds also available.
The following is a selection of bearded irises that have gained the Royal Horticultural Society's Award of Garden Merit:-
Bearded Iris Oncocyclus section
This section 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.
Bearded Iris Regelia section
This section, 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.
Beardless Rhizome Iris (subgenus Limniris)
There are six major subgroupings of the Beardless iris, depending on origin. They are divided into Pacific Coast, Siberica, Spuria, Louisiana, Japanese, and other.
Beardless rhizomatous iris types commonly found in the European 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 (hanash?bu), the Blood iris (I. sanguinea, ayame) and the Rabbit-ear iris (I. laevigata, kakitsubata). I. unguicularis is a late-winter-flowering species from Algeria, with sky-blue flowers blotched with yellow, produced from Winter to Spring. Yet another beardless rhizomatous iris popular in gardening is I. ruthenica, which has much the same requirements and characteristics as the tall bearded irises. In North America, Louisiana iris and its hybrids are often cultivated.
Crested Rhizome Iris (subgenus Limniris)
One specific species, Iris cristata from North America.
Bulbing Juno Iris (subgenus Scorpiris)
Often called 'junos', this type of iris is one of the more popular bulb irises in cultivation. They are generally earliest to bloom.
Bulbing European Iris (subgenus Xiphium)
This group includes irises generally of European descent, and are also classified as Dutch, English, or Spanish iris.
- Iris reticulata and Iris persica, both of which are fragrant, are also popular with florists.
- Iris xiphium, the Spanish Iris (also known as Dutch Iris) and
- Iris latifolia, the English Iris. Despite the common names both the Spanish and English iris 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.
Bulbing Reticulate Iris (subgenus Hermodactyloides)
Reticulate irises with their characteristic bulbs, including the yellow I. danfordiae, and the various blue-purple I. histrioides and I. reticulata, flower as early as February and March. These reticulate-bulbed irises are miniatures and popular spring bulbs, being one of the first to bloom in the garden. 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 coco-fiber.
Source of the article : Wikipedia
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