Louisiana Or Hexagona Irises

In Europe, the stately form of iris flowers has been recorded for hundreds of years; in Egypt and the Mediterranean this can be extended to thousands. Ancient works of art preserve stylized forms of I. pseudacorus, the flag iris, and I. germanica, an ancestor of our modern bearded irises. Use of these plants for medicinal purposes is well-documented. But in the southern United States there exists a group of irises that aroused little botanical interest until about one hundred years ago, though no doubt the plants were admired for centuries previous by Indians.

Generally known as Louisiana irises, they flower in spring, usually April-May in the northern hemisphere and October-November in the southern hemisphere.

The many varied cultivars that exist today have been bred from the five species and their natural hybrids, most of which come from the Mississippi Basin, though one, I. hexagona, is native to the swamps of Florida, Alabama and Georgia. Named for the six prominent ribs on its seed cage, it gives its name to the group and was first described in 1788. Descriptions of the species I. fulva and I. brevicaulis followed some years later. But the remaining two species in this group were not described until last century: I. giganticaerulea in 1929 and I. nelsonii in 1966, after being "discovered" during the late 1930s.

In the early 1900s, these irises grew in great profusion in the swamps and bayous near what is now downtown New Orleans.

Although numbering only five species, their varying characteristics provide a huge range of possibilities for breeding cultivars to widely differing specifications. The natural hybridization that had occurred before they were "discovered" had already introduced a wider range of color variations than exists in any other iris apart from bearded irises.

So how does the novice iris grower recognize a Louisiana iris? It's not always easy. The form of the flower can vary widely, from slender and drooping to rounded, ruffled and frilly with some hybrids looking not unlike modern Siberian cultivars. Often the standards and the falls overlap each other, so that viewed from above the bloom appears to be composed of two rounded triangles superimposed one on top of the other. Imagine a curvy version of the Star of David. Though flower colors vary enormously, true fire-engine red has not yet been attained in an iris of any kind but the reddish coloring of I. fulva produces cultivars with more definite red than is found in other series of irises.

Culture

Louisiana irises have three major needs: they must have an adequate supply of water, the soil must be acidic in composition -any soil suitable for camellias and azaleas is fine -and it must be fertile. These three, unlike climate, can largely be controlled by the grower, and Louisiana irises are being successfully grown in widely varying climates, though with a corresponding difference in length of growing season and time of flowering.

Louisiana irises start blooming in early spring (mid to late March) and grow for about eight months of the year. In Los Angeles, California, where summers are drier than in Louisiana, the growing season is close to 12 months, provided they are watered adequately. The normal blooming period starts in mid-spring (mid to late April).

Surprisingly, these irises will also grow in the cold midwest, where the climate could scarcely be more different from that of their natural habitat. There, Louisiana irises survive the frozen winters either insulated by heavy snowfalls or, lacking snow, with the protection of a heavy mulch. They grow for about five months and flower for a long season in summer, often starting in the second week of June and continuing into July. There is some doubt, however, about the cold hardiness of cultivars bred from I. hexagona. Generally speaking, the smaller the stature of the iris, the more cold-tolerant it tends to be.

Though Louisiana irises enjoy warmth and basking in the full sun they will cope happily with half a day's sunshine or all-day filtered light, yet another example of their adaptability.

In areas where summers are very hot they will need some heat protection: mulching is effective, while also conserving moisture and restricting weed growth.

Louisiana irises like rich, heavy soil and will grow happily in regular beds, at the edge of water, in a bog, in standing water preferably to a depth of not more than 1 in (2 cm), or in pots placed in ponds.

They are also ideal irises to grow as container plants for the patio, as long as they are given adequate water. In spring, when they make rapid growth, and during the flowering season, sit the container in a saucer continually filled with water. They are heavy feeders too, so when potted, they will need frequent fertilizing. Well-rotted animal manures are good. Remove the saucer of water once flowering is over - this imitates its natural habitat, where the swamps often dry out in summer.

Remember that the foliage nourishes the plant and during their summer dormancy most Louisiana irises will grow better if they are kept watered during hot dry spells. In late summer and fall, resist the temptation to pull off dead foliage as this can damage the rhizome increase. Dead leaves will eventually shrivel up and blend into the mulch.

Planting and division

In keeping with their extremely adaptable nature, Louisiana irises can be moved at any time of the year, but it's usual to plant and divide them straight after flowering, or in the fall. To divide, dig the rhizomes and cut back the foliage to about 8 in (20 cm). Rhizomes should be planted about 1 in (3 cm) deep. When Louisiana irises are planted or replanted, it's a good idea to allow time for new roots to develop before giving them lots of water. This avoids the risk of rhizomes rotting in wet soil before their roots are ready to suck up the moisture. It follows that irises planted in pots and intended to be grown in water need about four weeks to develop roots before they are submerged.

These irises tend to increase fast, particularly when submerged, and ideally should be divided every three years as flowering diminishes if the clumps become too cramped.

It is not only the flowers of Louisiana irises that are eye-catching; their seed pods can be huge and add another dimension to the garden, hanging from their stalks like great big green eggs. But they are heavy. If you want to save seed you will need to stake your plants once the seed pods form. Louisiana seeds come with a corky covering that allows them to float and helps to explain their wide dispersal in their swampy homeland.

Once this covering dries out, though, germination is more difficult, so in mild climates seed should be planted immediately once it ripens. In cold climates, however, it should not be planted until spring. Plant the seeds in pots, in a planting mix that is fertile and porous -a medium of equal parts of sand and well-rotted manure works well. Cover them with about 1/2 in (1 cm) of mix and keep them moist and shaded.

Wait until the seedlings have developed a good root ball before attempting to plant them out. They can be almost root-bound and as tall as 6-8 in (15-20 cm) before there is any need to move them. Expect to see flowers in the second season.

Characteristics

The flower stalk of Louisiana irises should be straight or gracefully curved, except in the case of varieties with I. brevicaulis in their background-those will have the zigzag characteristic of that species. The height of the stalk should be in proportion to the blooms. Flower buds should be spaced so that there is no interference with the foliage, and there should be a minimum of six buds per flower stalk. As to flower form, any form is acceptable that is typical of that variety. The flower color should be fresh and clear. All of the primary colors and their combinations are found in the Louisiana species and their hybrids. Louisiana irises may have flowers of bright, pleasing, blended colors and bicolors with harmonic color contrasts. They may display new color patterns including pronounced veining, spray patterns or halos.

Louisiana irises have flowers of many types including forms that are flat, flaring, pendent, recurving, open, overlapping, cartwheel and double or semidouble. The standards and falls may be ruffled. The style arms, very important to the beauty of these irises, may be in a different color than the standards and falls or they may be ruffled or edged with a different color. Signals, markings that may appear in the same location where beards are found in bearded irises, are typically orange or yellow and vary from nearly absent to very large. Some Louisiana iris cultivars have signals on both standards and falls and some have line signals referred to as crests that are raised and pubescent. There is so much variety to Louisiana irises that one must know a great deal in order to judge what is the ideal for the varieties.

Marvelous plants for a bog or water garden, the Louisiana irises also are handsome choices for herbaceous beds and borders. They are beautiful as cut flowers and easy to arrange. When the flower stalks are cut, the buds continue to open and the flowers will last several days. The flower stalks range from 1 to 5 feet in height.

Not as widely known as the bearded irises every gardener grows, the Louisiana irises have many variations in flower form and size as well as color, making them fascinating choices for perennial gardens. The flowering period, which follows that of the bearded irises, can last from six weeks to two months, an advantage not found in many perennials.

Species

I. hexagona

This iris comes from the southeastern United States, adjacent to the Atlantic coast and the Gulf of Mexico, so it likes warm summers and mild winters. The flowers are a gorgeous blue, sometimes varying towards lavender, with a narrow yellow signal on the falls, and standards that are upright and slim. The branching stems vary in height, from 12-36 in (30-90 cm), and as with all Louisiana irises, it has sword-like, yellow-green foliage.

I. brevicaulis

Is another blue-flowered species, generally paler than I. hexagona, with an open form. It is the dwarf of the species in this group and it occurs further north than I. hexagona, often found in open pasture where moisture is high during the growing season. With much shorter stalks -10-14 in (25-35 cm) -than its cousins, the flowers are always carried low, never appearing above the foliage. I. brevicaulis is quite hardy and in Louisiana flowers in early to mid-May, later than the other species. A notable feature is the stalk, which zigzags at the nodes.

I. giganticaerulea

As the name suggests, is also blue-flowered, though it may vary somewhat through shades of wisteria and lavender to white. Stalks are tall and straight, occasionally growing to 66 in (165 cm). The slender flowers are carried above the foliage, giving the plant an air of elegance, especially when grown in clumps. This is a plant that likes rich soil and thrives in flooded conditions, growing in full sun or partial shade in open swamps.

I. fulva

This iris s a robust plant ranging in height from 18-32 in (45-80 cm). It is notable for its dull red, coppery, orange-red, even (rarely) chrome yellow flowers, borne on stems that are almost straight. Both falls and standards are drooping, and the short, semi-erect style arms look like a butterfly sitting atop the bloom. This iris caused a sensation in Britain when it first arrived in 1814 because of its color. It occurs abundantly in Louisiana but has been found as far north as Ohio, growing in partial shade to full sun, in open swamps, in wooded swamps where light is sufficient, and alongside streams and canals. Usual flowering time is early summer and this iris is one of the easiest to grow.

I. nelsonii

This iris was not "discovered" until 1938 and occurs naturally only in a very limited area south of Abbeville in Louisiana. This iris is a tall-growing plant with stalks that may reach 44 in (110 cm) and are often branched, while the flowers have long reflexed falls and standards, creating a bloom of rather languid appearance. The flower, varying in color from red to a dull terracotta with a hint of lavender, is similar to that of I. fulva, and like it, has made it possible for hybridizers to introduce red into their breeding programs. For this reason it is a very important member of the Louisiana family, having contributed to many of the incredibly beautiful modern cultivars.