Some varieties of the bearded Iris bloom a second time in the late summer or fall, hence the name rebloomers. In general, these stand more water and more "food" for performance than to regular varieties. And, while in the near past it was true that the rebloomers' quality of bloom was lower than that of the true spring bloomers, many modern varieties show bloom of equal quality with the bonus of repeat bloom.
Culture of Bearded Iris
The bearded iris is very popular, adapting quite well to the hot summer temperatures. These irises offer carefree blooms in nearly every color of the rainbow. They are easy to establish and require a minimum of maintenance. Petals that vary in texture from the most plush velvet, to the finest silk, often on one flower, provide variety to suit almost every taste.
Unlike most spring bulbs, bearded iris don't require a period of cold to produce blossoms, making them perfect for areas with mild winters. They are also extremely drought tolerant, good for areas with little or no summer rains-- e.g. the San Joaquin Valley!
These bearded Iris are the result of crossing the exotic but demanding species Iris of the Near East with the other bearded Iris. Varieties with less than or equal to 1/4 Aril blood can usually be grown under the same conditions as the Tall Bearded Iris. The higher the percentage of Aril Blood, the greater the need for perfect drainage, clean cultivation, alkaline soil, and dry summer conditions. Also, the greater the chances that the foliage will die down during the summer and reappear in the fall.
This garden class includes the 350+ botanical species and is the root of all the preceding classes. Since these wildflowers come from every type of environment from desert to swamp and mountain top to grassland, the culture of each needs to be specified individually.
Sometimes called the dinner plant Iris, Japanese Iris have a "flat" flower composed of three (single type) or six (double type) petals. They require acid soil with lots of humus and plenty of water during growth. Indeed, they are often used in small pounds for ornamentation. On some varieties (and depending on the severity of your winters) the foliage will die in the winter and reappear in the spring. Flowering height varies greatly with culture and may reach 3' to 5', but is usually somewhat less.
The Louisiana Iris are derivatives of the Iris species of the Gulf Coast states. The hybrids have flower forms varying from nearly flat to gracefully drooping. Like the Japanese they require acid soil and plenty of moisture. Unlike many Iris they are tolerant of partial (but not dense) shade and will thrive under bog conditions. They do, however, need lots of room since the rhizomes tend to "walk" or grow very long rather than staying in a tight clump. Heights range from 2' to 5'.
Culture of Beardless Iris
In general the beardless Iris should be dug and/or planted in the fall as opposed to the summer for the bearded Iris. The rhizomes should be planted a little more deeply than those of the bearded Iris and must be kept moist until the plants are established. Unless noted otherwise, they bloom after the tall bearded Iris.
The Siberian Iris should be planted where they can be left for several years, since their beauty lies in the bouquet effect given by an established clump in full bloom. They require acid soil and sharp drainage and are not difficult to grow if you can provide a soil which is constantly moist but never soggy. These Iris go dormant in the fall with new growth appearing in the spring. Flowers are held on 1 1/2 ft. to 3 ft. stems on well established clumps.
PACIFIC COAST NATIVE IRIS
A highly variable group, the Pacific Coast Native Iris are graceful derivatives of the Iris native to the Pacific Coast. They need acid soil with sharp drainage and much moisture during the fall, winter and spring. Watering should be held to a minimum during the summer when the plants are dormant. Foliage varies from evergreen to semi-deciduous with flowers on 6" to 2' stems, depending on the variety. Time of bloom also varies widely from one variety to the next -- the first come before the main Bearded Iris season, others bloom in late May early June, and some rebloom. In all but truly coastal climates, they should be grown in filtered shade. A few varieties should be divided annually, otherwise they tend to bloom out; most resent transplanting and should be left until crowded.
The medians are the little cousins of the tall bearded Iris. Their general culture and flower form are the same except that the smaller the plant, the shallower the root system, the more frequent the need for watering and the earlier the bloom season. The types of medians are defined by the height of the bloomstalks and the time of bloom except for the Miniature Tall Bearded Iris which are bred for small flowers on graceful wiry stems and foliage in proportion.
The types are: Miniature Dwarf Bearded, Standard Dwarf Bearded, Intermediate Bearded, Border Bearded and Miniature Tall Bearded.
The Spurias are among the best Iris for cutting with flowers similar to the Dutch Iris (florist Iris) forming along one side of tall rigid stems. Their narrow, upright growth habit makes them excellent for use as vertical accents in the garden. They are also the only beardless Iris which prefer a mildly alkaline to neutral soil. They require ample moisture during fall, winter and spring, and will go dormant if water is withheld during the summer. However, they require heat (full sun) in order to bloom well. Many of the modern hybrids bloom on stalks in the 4' to 6' range, but expect bloom to be shorter and somewhat sparse the first spring after planting.