This article is
about the Iris plant. For other uses, see Iris (disambiguation).
Other plants
named "iris" are found elsewhere in the Iridaceae.
Iris is a genus
of 260–300 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
often-segregated, monotypic genera Belamcanda (blackberry lily), Hermodactylus
(snake's head iris), and Pardanthopsis (vesper iris) are currently included in
Iris.
Distribution
The genus is
widely distributed throughout the north temperate zone. Their habitats are
varied, ranging from cold and montane regions to the grassy slopes, meadowlands
and riverbanks of the northern hemisphere.
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 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 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, these bear an aril.
Systematics and taxonomy
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.
Cultivation
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. Irises, especially the multitude
of bearded types, feature regularly in shows such as the Chelsea Flower Show.
Irises 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 (Northern
Hemisphere), followed by the dwarf forms of I. pumila which blossom in Spring,
followed in early Summer by most of the tall bearded varietis, 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.
Bearded rhizomatous irises
The most
commonly found garden iris is the bearded German Iris (I.
germanica) 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 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 varieties.
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. 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 which have gained the Royal Horticultural
Society's Award of Garden Merit:-
'Alizes' (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)
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.
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 rhizomatous (subgenus Limniris)
irises
Beardless
rhizomatous iris types commonly found in the 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 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.
Reticulate-bulbed (subgenus Hermodactyloides)
irises
Reticulate
irises with their characteristic bulbs, including the yellow I. danfordiae, and
the various blue-purple I. histrioides, I. reticulata, as well as the
smooth-bulbed I. filifolia, 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 cocos-fibre refuse.
Aromatic rhizomes
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" or Orris Oil.
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.
Water purification
Further
information: Organisms_used_in_water_purification
Further
information: Treatment_pond
In water
purification, Yellow Iris (I. pseudacorus) is
used. The roots are usually planted in a substrate (e.g. lava-stone) in a
reedbed-setup. The roots then improve water quality by consuming nutrient
pollutants, such as from agricultural runoff.
In art and symbolism
An iris –
species unspecified – is one of the state flowers of Tennessee . Tradition holds that the
particular iris symbolizing Tennessee
is a purple cultivar, to go alongside the wild-growing Purple Passion Flower
(Passiflora incarnata) which is the state's other floral emblem. Greeneville , Tennessee
The artist
George Gessert has specialised in breeding irises.
The artist
Vincent van Gogh painted several famous pictures of irises.
The American
artist, Joseph Mason — a great friend of John James Audubon — painted a precise
image of what was then known as the Lousianna Flag or Copper Iris (Iris cuprea)
to which Audubon subsequently added two Northern Paraula birds (parula
americana) for inclusion as Plate 15 in his Birds of America.
The artist
Philip Hermogenes Calderon painted an iris in his 1856 work Broken Vows; he
followed the principles of the Pre-Raphaelite Brotherhood. An ancient belief is
that the iris serves as a warning to be heeded, as it was named for the
messenger of Olympus . It also conveys images
of lost love and silent grief, for young girls were led into the afterlife by
Iris. Broken Vows was accompanied with poetry by Henry Wadsworth Longfellow
when it was first exhibited.
The
fleur-de-lis, a stylized iris, first occurs in its modern use as the emblem of
the House of Capet. The fleur-de-lis has been associated with France as Louis
VII adopted it as a symbol in the 12th Century. The yellow fleur-de-lis
reflects the Yellow Iris (I. pseudacorus), common in Western
Europe . Contemporary uses can be seen in the Quebec
flag and the logo of the New Orleans Saints professional football team, and on
the flag of Saint Louis , Missouri
The red
fleur-de-lis in the coat-of-arms of Florence (Italy ) descends from the white iris which is
native to Florence
and which grew even in its city walls. This white iris, displayed against a red
background, became the symbol of Florence
until the Medici family, to signal a change in political power, reversed the
colors making the white one red and setting in motion a centuries-long breeding
program to hybridize a red iris.
Furthermore, the
fleur-de-lis is the almost-universal symbol of Scouting and one of the symbols
adopted by the sorority, Kappa Kappa Gamma.
A stylized
Yellow Iris is the symbol of Brussels ,
since historically, the important Saint Gaugericus Island was carpeted in them.
The iris symbol is now the sole feature on the flag of the Brussels-Capital
Region.
The provincial
flower of Québec (Canada ) is
the Harlequin Blueflag (I. versicolor), called
iris versicolore in French.
Pictures
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