Iris are found in many landscapes, providing graceful flowers in an endless array of brilliant colors. The bold sword shaped foliage is also an excellent contrast to the more traditional or mounded forms of garden plants.
There are hundreds of species and cultivars of iris, varying from tiny woodland groundcovers to dramatic flowers for sunny landscapes to species that thrive in water-logged conditions. There is an iris for virtually every condition in the garden.
The most common iris types growing in Louisiana landscapes are the bearded iris (Iris germanica), Japanese iris (Iris ensata), Siberian iris (Iris sibirica) and the Louisiana iris (Iris spp.).
Bearded iris is a hardy, long-lived perennial that require a minimum of maintenance. The flowers have six petals; three upright petals (called standards) and three hanging petals (called falls). A fuzzy line or beard runs down the middle of each fall.
September is a good month to plant these iris. This will allow them to become well established before winter. In a well-prepared bed, dig a shallow hole large enough to accommodate the rhizome or clump of rhizomes. Form a mound of soil in the center for the planting base. Make the mound high enough so the top of the rhizome is slightly above soil level. Spread the roots around the mound, fill with soil, and water.
For a mass of color, plant at least three rhizomes (spaced 8 to 10 inches apart) or plant undivided clumps; point each fan of leaves away from the center of the group. Clumps should be spaced 18 inches apart.
After three to five years, iris generally become crowded and should be divided. Iris can be divided any time, but many growers prefer to divide four to six weeks after the flowering period. Cut the leaves to one-third their length. Dig the clump and wash soil off with a hose. Cut rhizomes apart so that each section has at least one healthy fan of leaves and firm, white roots.
Japanese iris require a slightly acid soil (pH 5.5-6.5) and have the most spectacular flowers of all the iris. Blooms are usually huge, ruffled and flat in form; some are marbled with gray or white. They bloom about a month after tall bearded. Japanese iris will flourish in wet environments. These iris are heavy feeders and require lots of organic matter for nutrients. They need six hours of full sun.
Bare root plants should be soaked in cool water for a few hours or overnight. Plant individual rhizomes 2-3 inches deep and 6 to 8 inches apart. Water in well to start the root development, do not let new transplant dry out. Depending on your soils and weather a daily watering may be needed for the first week or two. Planting in a shallow depression will allow you to flood irrigate the plants.
These iris should be planted in summer to early fall or may be divided best in early spring before growth starts.
The Siberian iris will tolerate a wide range of soil moisture conditions, thriving in damp and even wet areas, since they grow from fibrous roots rather than fleshy rhizomes. They also bloom in partial shade — though not as well as in full sunlight.
Plant these iris in late summer to early fall. The plants should be removed from their packaging promptly and soaked overnight prior to planting. They should be planted with the crown just under the soil surface, and then watered in. There are two opportunities for dividing Siberian iris. Divide in early spring as new growth just appears or late summer or early fall, cut back the foliage to about six inches, then dig and divide.
The original Louisiana iris species often grow in swampy or boggy conditions but these and their hybrids can be grown in ordinary garden beds.
The best time to plant and divide Louisiana iris is mid-to late August and September. Plant the rhizome so it is at or just below the soil surface. Louisiana iris should be grown in a site with full sun, a pH of 6.5 or lower with high fertility and organic matter. Watering is critical during the growing season. The most important times to water are early in the growing season and in the spring.
Remember — when gardening, have fun, be creative, be informed and be safe
For answers to your specific gardening questions contact Steven Hotard, Area Agent in Horticulture/Forestry with the LSU AgCenter in Ouachita Parish at 323-2251 or by email at email@example.com.