'' in China 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. Generally, Irises grow well in most garden soil types providing they are well-drained, depending on the species. The earliest to bloom are species like
I. reticulata and
I. reichenbachii, which flower as early as February and March in the Northern Hemisphere, followed by the dwarf forms of
I. pumila and others. In May or June, most of the tall bearded varieties start to bloom, such as the German iris and its
variety florentina, sweet iris, Hungarian iris, lemon-yellow iris (
I. flavescens),
Iris sambucina, and their natural and horticultural hybrids such as those described under names like
I. neglecta or
I. squalens and best united under
I. × lurida. The iris is promoted in the United Kingdom by the British Iris Society. The
National Collection of
Arthur Bliss Irises is held in
Gloucestershire. The American Iris Society is the
International Cultivar Registration Authority for
Iris, and recognises over 30,000 registered cultivar names.
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) Bearded iris 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 of tall bearded iris). 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. Irises like many related
genera lack red-based hues because their
anthocyanins are
delphinidin-derived.
Pelargonidin-derived anthocyanins would lend the sought-after blue-based colors but these genera are metabolically disinclined to produce pelargonidin. (tall bearded, blue & white) • 'Bumblebee Deelite' (miniature tall bearded, yellow/purple) • 'Early Light' (tall bearded, pale yellow) • 'Jane Phillips' (tall bearded, pale blue) • 'Langport Wren' (intermediate bearded, maroon) • 'Maui Moonlight' (intermediate bearded, pale yellow) • 'Orinoco Flow' (border bearded, white/violet) • 'Raspberry Blush' (intermediate bearded, pink) • 'Sarah Taylor' (dwarf bearded, pale yellow) • 'Thornbird' (tall bearded, pale yellow) • 'Titan's Glory' (tall bearded, deep blue)
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. Species of section
Oncocyclus are generally strict endemics, typically occurring in a small number of scattered, disjunct populations, whose geographical isolation is enhanced by their pollination strategy and myrmecochory seed dispersal. Morphological divergence between populations usually follows a cline reflecting local adaptation to environment conditions; furthermore, this largely overlaps divergence between species, making it difficult to identify discrete species boundaries in these irises. 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 (
hanashōbu), 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 with a yellow streak in the centre of each petal, 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 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. ==Uses==