Irises

Irises belong to the family Iridaceae which includes freesias and gladioli, plants that, to the casual observer, have nothing in common with the iris. The family also includes plants that look very much like irises, yet are classified under other names. Such plants are Moraea from South Africa, Tigridia from South America, and Dietes, a real iris look-alike, also from South Africa. But no true iris is native to the southern hemisphere.

History of irises        The anatomy of irises            Propagation of irises          Landscaping with irises     Pests and diseases of irises

Widely dispersed across Europe, Asia and parts of North America, irises are recognizable by the arrangement of their floral parts in multiples of three. They have six floral segments (or petals) in two sets -the standards and the falls. Standards are named for their tendency to sit upright; falls tend to droop and are often broader than the standards. These parts are merely the decoration, and have no role to play in the reproduction of the plant.

As well as the falls and standards, irises have three style arms that are evident when you look down on the bloom. These radiate from the center of the bloom, overlaying the falls and adding to the beauty of the flower with their distinctive colors. But they have a specific purpose: they are extensions of the ovaries, which contain the egg cells. Once pollinated, the ovary swells to become the seed pod. Styles, ovaries, stigmas and anthers all constitute the sexual or seed-forming parts of the iris.

Bewitching to look at, the often surreal color combinations created by the different parts of the flower are not produced merely for humans to marvel at, though they play a large part in making us fall in love with the plant. The iris is flaunting its beauty to attract pollinating insects. This attraction is enhanced by a feature on the falls, a landing strip that tempts the insect closer to the flower. On beardless varieties it may be a bold bright signal, a stripe in a contrasting color or a frilled crest. Stand for a few moments one warm sunny day when the irises are in flower and watch a bumblebee head straight for the narrow slot created by the style arms spreading over this patch at the top of the falls. The bee disappears as if through a secret trapdoor, greedy for the nectar found at the base of the flower, and in the process fertilizes the plant.

The genus consists of more than 200 species, many of which have hybridized naturally in the wild, cross-pollinated by insects. This sometimes makes it difficult, when "new" finds have been made, for botanists to distinguish between true species (i.e. a plant having characteristics it does not share with any other plant in the same genus), and natural hybrids. Classification still continues and as new, genetic information comes to light, name changes occur from time to time.

As hybridizers work their magic -breeding new cultivars -the most visible effects of their alchemy are increasing color ranges in particular series, and flowers that have changed in shape from the species. In many cases, the falls have become broader and, especially in the case of Japanese irises, more horizontal. Standards often have become less upright.

Substance is the term used to refer to the thickness of the floral parts: the more substantial the petals, the longer the flower tends to last, either on the plant or as a cut flower, and the better is its resistance to heat, rain and wind. But where fragility is part of the charm of a particular flower, increased substance may not necessarily be regarded as an improvement. Texture refers to the surface of the floral parts; they may be velvety or silken, glossy or mat, smooth or papery.

With the advent of the chemical breeding of tetraploids (plants with cells that contain four sets of chromosomes instead of the usual two), and the crossing of natural tetraploids (in the case of bearded irises), hybridizers started creating flowers which are larger, more ruffled, more flaring in form, and richer in color, while various features of the plant are emphasized. The leaves and stalks are frequently thicker and a deeper green, the substance of the petals or their velvety texture may be exaggerated. lrisarians can be passionate about their favorite flowers.

Hybridizers also look to increase the all-around garden performance of irises, to create plants that are healthier and more floriferous, that will produce more branches, that will flower more than once in a season (remontancy) , or that will tolerate a wider range of climate differential. And the search is on to create a truly red iris though there are now some Louisiana irises that come close.

Most gardeners choose irises for their stunning color or for their classic form. But as members of a community of plants, foliage and behavior throughout the seasons become important design factors. After all, the foliage will still be there, irritating or satisfying, long after the blooms have faded, and all irises have foliage that defines the shape of the plant.

Foliage of the tiny spring-flowering Reticulatas can be less than appealing once the flowers have gone; but the leaves need to remain on the plant to replenish its resources for the following season. So it's a good idea to plant these early-flowering irises where their foliage will be hidden by the new growth of later developing spring plants.

Dwarf Bearded irises also flower early in spring, but in contrast to Reticulatas their foliage is still handsome in mid-summer, providing fans of upright light green blades -an attractive focus in the front of the border among low, sprawling perennials.

Siberian irises, on the other hand, form tall graceful fountains of fine grass-like foliage that in themselves become a garden feature until they die down in the fall. So, once seduced by the flower of a particular iris, it's a good idea to consider carefully where it will look best.

Soils vary considerably in their composition, from extreme acidity to extreme alkalinity, the relative measure being expressed as the pH value; 7 is neutral. A pH reading of 6.5 and lower indicates soil of acidic composition with the level of acidity increasing as the number decreases. A reading above 7 indicates that the soil is alkaline, and the higher the number, the higher the alkalinity. Some irises like soil that is alkaline in its composition; many require an acidic soil. Providing the right soil for the kinds of iris you want to grow is very important. So too is the amount of moisture that is required. Think about where the iris grows naturally and then try to simulate those conditions as closely as possible. Obviously, if you garden at sea level you cannot do much to increase the altitude but, depending on what your favorite iris requires, you can ensure that the ground is boggy or well-drained or somewhere in between. And you can add nutrients to the soil to adjust its chemical composition. Agricultural sulfur, rotted animal manure, pine needles and leaf mold all help to maintain the acidity of the soil. Treating it with lime or dolomite will increase its alkalinity.