Monday, September 20, 2021

Iris BOTANY AND GEOGRAPHY

By Sylvain Ruaud

The iris, a universal plant? If we rely on the number of countries or regions associated with it, it seems that there are irises from all over the world. In the following lines we will make a kind of world tour of irises, referring to the names that have been given to them, whether in their botanical name or in their vernacular name.


Iris of England


The iris known as “English iris” is actually the species I. latifolia or X. latifolium. Native to the Pyrenees and the north of Spain, it can be found, for example, in abundance in the Gavarnie cirque and the Tourmalet pass, on the mountain slopes. In the inexhaustible source of information that is the Internet, one can read this comment: "This erroneous name comes from the fact that around the year 1600, the convent of Eichstätt in Germany received the first large ovoid bulbs from England, which made the monks believe that this iris grew spontaneously near Bristol. Thus, cultivated under the name Iris bulbosa angliana, this plant became the iris of England. Maurice Boussard, a French specialist in iridaceae, developed the same information and, botanically, he added: "(The English iris) belongs to the Xiphium group (bulbous iris) which does not hybridize with any other species. The flowers range from white to purple and dark blue, through various shades of purple." (1)


Iris of Spain



Is there any confusion between the so-called Spanish iris and the English iris? Both are Xiphiums, but Maurice Boussard makes the distinction: "We group together under (the name of Spanish Iris) a set of natural or man-selected varieties of Xiphium vulgare, a botanical species spontaneously spread in the Iberian Peninsula (Spain and Portugal), with flowers in a variety of colors. The name of this species corresponds well to its geographical location, which is not the case of the irises of England.  The species and its varieties are part of the irises cultivated for cut flowers. (1) About the color of the flowers, Richard Cayeux, in "The iris, a royal flower" specifies that these colors are "always marked by a yellow spot on the sepals."


Iris of the Netherlands


While we are at it, let's stay in the Xiphium group because the irises of Holland constitute "a series of horticultural irises obtained by hybridization between two botanical species of bulbous iris of the Xiphium group (...)"(1) The colors obtained, and that we can see in the bouquets of florists, but also in our gardens when the bulbs are planted there, are in the tones of blue with a yellow spot on the sepals. It has become a very common plant.


Iris of Germany


It is the very famous I. x germanica, that we all know and that, for centuries, illuminates our gardens at the end of winter, with its flowers generally of a dark purple, but that can, because of innumerable spontaneous crossings, take all kinds of tones, from blue to purple. There has been much discussion about whether it is a true species or simply naturalized varieties. "It is characterized by its more or less evergreen foliage in winter and its large, fragrant purple spring flowers whose three erect, dome-shaped petals are lighter in color than the three drooping sepals, adorned with a bright yellow beard." (1) Its half-buried horizontal rhizome elongates through the tip, which bears leaves and stem, and laterally forms new growth points. It can be said to be one of the starting points of all bearded iris hybrids.


Iris of Italy


Let's continue our tour of Europe. The Italian iris is not strictly speaking a species, nor even a variety, but a local version of Iris x germanica, in its white form better known as I. Florentina, as well as Iris pallida, cultivated in Italy and much sought after in perfumery for the rhizome, from which the essence of iris is extracted, after a long and laborious preparation which makes its price.


Iris of Dalmatia


It is about Iris pallida which everyone agrees to say that it is native of Dalmatia, the region located in current Croatia, all along the coast of the Adriatic Sea. In June, flowering stems rise to the top of the foliage and bear flowers similar to those of Iris x germanica but of a pale blue color, deliciously perfumed. The Dalmatian iris, like the Italian iris, has a fragrant rhizome and is therefore cultivated for perfumery.


Iris of Algeria


Let us cross the Mediterranean to the iris of Algeria (or Algiers, quite simply). It is what botanists call I. unguicularis. It is Richard Cayeux who speaks best about it: "This iris of Algiers presents the great interest of a perfumed and winter bloom (in fact, from mid-November to mid-March). The relatively short-lived flowers are renewed for almost four months"(2) The color varies from white (variety 'Winter's Treasure') to bright mauve. This plant is widely grown in temperate regions, and many cultivars have been selected for ornamental gardens.


Iris of Siberia


Everyone who is interested in irises knows the Siberian iris. The species I. sibirica with thin, woody rhizomes and narrow, long and flexible foliage, which grows preferably in a humid environment and gives lovely blue flowers, is mainly classified under this name. It is found in Central and Eastern Europe, as well as in the Caucasus. In France, it is a rare and protected plant, which one meets in Alsace like in the Jura and, perhaps, still sometimes in certain meadows which border the river Charente.


There are very numerous and gorgeous hybrids of it. These, nowadays, exist in almost all colors. Siberian irises are now a large family of garden flowers, particularly decorative.


Iris of Lebanon


The Near and Middle East is full of irises of all kinds. It is even known that the tetraploid ancestors of our great garden irises come from these regions. The iris of Lebanon or Iris sofarana is endemic to the mountains of Lebanon. It is a species in great danger because of the political and economic circumstances of its country, but also because of its beauty, which makes it the prey of unscrupulous collectors. It belongs to the group of I. susiana (Susa iris) together with(Damascus iris), a group with huge and darkly colored flowers, very spectacular, but difficult to cultivate outside its region of origin.


Iris of Palestine


Let's stay in the same region, to admire the iris of Palestine (I. palaestina), an exotic flower classified among the Junos, which some authors renounce to classify among the irises.  These unusual plants can be described as follows: they have thick, fleshy roots that are maintained during the dormant period and are easily damaged. The flowers, which are born in the axils of the leaves, are superb in their variety of colors; they differ from the traditional iris form by their tiny petals which are either hanging or held horizontally. The flowers, either grayish green, or rather yellow, bloom at the end of the winter and are pleasantly perfumed.


Now let's go to the Far East to meet...


Iris of Japan


In the series of LAEVIGATAE there is among others I. ensata, which is the learned name of the iris of Japan. These flowers have been cultivated since time immemorial in Japan, where they enjoy an exceptional popularity. Here is what Richard Cayeux (2) says about them: "It is enough to have admired one day their flowers which seem to float in the air and their multiple associations of colors to understand (it). After the great garden irises, they are certainly the most cultivated hybrids in the world.”


Iris of Formosa


This time we are in the presence of what has long been called the "crested irises", which are part of the JAPONICAE series. I. formosana, and its cousin I. japonica are plants which do not lose their leaves, narrow and long, of a medium green, which carry flowers of small size, relatively numerous, on spindly but solid stems, white marked with lilac feathers and decorated with yellow ridges. They are very original flowers, easy to cultivate and whose bloom, in June, lasts approximately four weeks. I. formosana is native to the north-east of Taiwan, where it lives near forests, on the slopes of hills and on the slopes of roads, from 500-1000 m of altitude, which makes it a rustic plant.


To finish this long journey, we will cross the Atlantic and reach America.


Iris of Louisiana


Louisiana irises are man-made plants. The basic crosses were made between species of the HEXAGONAE iris series, native to the mouth of the Mississippi and surrounding areas: I. brevicaulis, I. fulva and I. giganticaerulea, to which Iris hexagona should be added. Later, I. nelsonii came to bring to the hybrids colors hitherto unknown in the group, and especially red. They are bulky and greedy plants, and are among the most beautiful of the iris world. Also, the most recent varieties are frost resistant. 


Iris of California


They are hybrids of rather recent appearance. Let us say that they appeared in the 1930s. Not in the United States by the way, but in Great Britain. At the beginning they were botanical species which were used, then interspecific crossings intervened, with an aim of joining the qualities of various species, all native of the West coast, between the State of Washington and that of California. The current cocktail is composed of a dozen species, but there are four that have been mostly used: I. douglasiana, I. innominata, I. tenax and I. munzii. The result is a hybrid that quickly forms strong clumps, which prefer acidic, well-drained soils, covered at flowering with numerous, usually round flowers, about 8 cm in diameter, in a remarkable choice of colors and patterns. 


Iris of Canada


Quebec, in Canada, has claimed the paternity of I. versicolor to the point of having made it its national flower, as legally as possible, in 1999. Iris versicolor is the American cousin of I. pseudacorus, an iris that grows in Europe in ditches and is covered with yellow flowers. I. versicolor is very similar to it. Its flowers, rather large but narrow, have sepals which flare at the point, which makes all their charm. Of blue or purplish color, they are decorated with a white signal and are tinted yellow or gold in the heart. It is this blue color that makes them commonly called "blue flag" in the United States. It is part of the LAEVIGATAE series. Its Asian origins give it a strong resistance to cold. I. versicolor lives preferably in a humid, even flooded environment, but it can also grow in a drier soil provided that it is watered copiously. It nevertheless needs an acid soil, rich in nutrients.


Thus ends our tour of the globe.


Whether they are botanical or horticultural plants, all these irises demonstrate the great diversity of the genus and attest to its worldwide distribution.


(1) Maurice Boussard, "L'ABCdaire des iris".

(2) Richard Cayeux, "L'Iris, une fleur royale".

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