Iris (plant)

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,[7] which are usually spreading or droop downwards, are referred to as "falls". They expand from their narrow base (the "claw" or "haft"[8]), into a broader expanded portion ("limb" or "blade"[9]) and can be adorned with veining, lines or dots. In the centre of the blade, some of the rhizomatous irises have a "beard", a row of fuzzy hairs at the base of each falls petal which gives pollinators a landing place and guides them to the nectar.[10]

The three,[7] 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 three styles[7] divide towards the apex into petaloid branches; this is significant in pollination.

Iris reichenbachii fruit

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 three[7] 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.[11]

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. Such as Iris stolonifera which as light brown seeds that have thick white aril (or coatings).[12]

• 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)

'Amethyst Flame'. Note prominent "beard".

Tall Bearded Iris 'Barocco'

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)[25] 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 "beard", short hairs arranged to look like a long furry caterpillar, is found toward the back of the lower petals and its purpose is to guide pollinating insects toward the reproductive parts of the plant. Bearded irises have been cultivated to have much larger blooms than historically; the flowers are now twice the size of those a hundred years ago. Ruffles were introduced in the 1960s to help stabilize the larger petals.[26]

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.[27] 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.[28] Pelargonidin-derived anthocyanins would lend the sought-after blue-based colors but these genera are metabolically disinclined to produce pelargonidin.[28] Dihydroflavonol 4-reductases in Iris's relatives selectively do not catalyse dihydrokaempferol to leucopelargonidin, the precursor, and this is probably the case here as well.[28] The other metabolic difficulty is the presence of flavonoid 3'-hydroxylase, which in Chrysanthemum inhibits pelargonidin synthesis.[28] The bias in irises towards delphinidin-anthocyanins is so pronounced that they have served as the gene donors for transgenic attempts at the aforementioned blue roses.[28] Although these have been technically successful – over 99% of their anthocyanins are blue – their growth is crippled and they have never been commercializable.[28]

The following is a selection of bearded irises that have gained the Royal Horticultural Society's Award of Garden Merit:

• 'Alizes'[29] (tall bearded, blue & white)
• 'Bumblebee Deelite'[30] (miniature tall bearded, yellow/purple)
• 'Early Light'[31] (tall bearded, pale yellow)
• 'Jane Phillips'[32] (tall bearded, pale blue)
• 'Langport Wren'[33] (intermediate bearded, maroon)
• 'Maui Moonlight'[34] (intermediate bearded, pale yellow)
• 'Orinoco Flow'[35] (border bearded, white/violet)
• 'Raspberry Blush'[36] (intermediate bearded, pink)
• 'Sarah Taylor'[37] (dwarf bearded, pale yellow)
• 'Thornbird'[38] (tall bearded, pale yellow)
• 'Titan's Glory'[39] (tall bearded, deep blue)

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.[40][41] 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.[42] 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.

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.

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.

One specific species, Iris cristata from North America.

Often called 'junos', this type of iris is one of the more popular bulb irises in cultivation. They are generally earliest to bloom.

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.

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.

Bombay Sapphire gin contains flavoring derived from particular bearded iris species Iris germanica and Iris pallida.

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.[43][44]

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" or orris oil.[45]

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.[46]

• Chancery of the Prime Minister, Kingdom of Belgium (2007): Brussels Town Hall. Retrieved November 11, 2007.
• Kamenetsky, Rina; Okubo, Hiroshi, eds. (2012). "Iridaceae". Ornamental Geophytes: From Basic Science to Sustainable Production. CRC Press. p. 24. ISBN 978-1-4398-4924-8.
• Mancoff, Debra N (2003). Flora Symbolica: Flowers in Pre-Raphaelite Art. New York: Prestel Publishing. ISBN 3-7913-2851-4.
• Pioch, Nicolas (2002). Gogh, Vincent van: Irises. Retrieved December 10, 2008.
• Species Group of the British Iris Society (1996). A Guide to Species Irises: Their Identification and Cultivation. Cambridge: Cambridge University Press. ISBN 0-521-44074-2.
• West, Ruth (2008). "George Gessert". Archived from the original on 2006-05-16. Retrieved December 10, 2008.

• Baker, John Gilbert (2012). "Systematic Treatment of the Genus Iris". American Iris Society.
• Dykes, William Rickatson (1913). The Genus Iris. Cambridge: Cambridge University Press. ISBN 0486230376.
• Harris, Gwenda (2011). "Classification of Irises" (PDF). New Zealand Iris Society. Archived from the original (PDF) on 2018-01-27.
• Mathew, Brian (1989). The Iris. London: BT Batsford. ISBN 978-0713460391.
• Lawrence, George Hill Mathewson (1953). "A Reclassification of the Genus Iris". Gentes Herbarum. 8: 346–371.
• Rodionenko, GI (1987). The Genus Iris L. (Questions of Morphology, Biology, Evolution and Systematics). London: British Iris Society. ISBN 9780901483300. (translation)
• Taylor, JJ (1976). "A reclassification of Iris species bearing arillate seeds". Proceedings of the Biological Society of Washington. 89: 411–420.
• Wilson, Carol (2004). Phylogeny of the genus Iris based on DNA sequence data. Rancho Santa Ana Botanic Garden. Archived from the original on 2014-06-02.