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Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved
Irises are among the best-known garden plants. There are about 200 species and all are native to northern temperate regions of the world. Tall bearded iris, the most common kind in Utah, are hardy, herbaceous perennials. Bearded iris get their name from the fuzzy fringe appendages located at the base of the falls. Many other attractive species of iris add interest and extend the bloom season in the garden.
Iris blossoms have three upright petals called standards and three handing sepals called falls. Some varieties have standards and falls of the same color while other varieties have standards of one color and falls of another. Iris come in almost every color including some that are almost black.
Originally, bearded iris were called German Iris. They have been hybridized so extensively that they are no longer assigned to specific species. They are now separated by height into dwarf, intermediate and tall varieties. Standard dwarf-bearded iris grow 8-15 inches tall, intermediate bearded iris are 16-27 inches tall and tall bearded iris are usually over 3 feet in height. By growing many different types you can have iris in bloom from early April until mid-June. Then the rebloomers produce more blossoms in the fall. This keeps the beds looking good.”
Bearded iris require eight hours of full sun and good soil drainage. Because they are sun-loving, plant the rhizomes within an inch of the soils surface. They grow well in any good garden soil but are less susceptible to diseases in moderately fertile soils. Heavy, rich soils tend to produce soft growth. This increases problems with soft rot.
One common mistake is that people plant their iris too close together. The plants increase three fans each year so allow two feet between the plants. Dig iris every three years and separating them. True irisiarians keep two of each variety (in case one doesn’t make it through a tough winter) and give the others away or compost them.
Overgrown iris clumps also cause a decrease in bloom stalks and bloom size -- another reason to divide triennially. After digging up your iris, mark the name (if known) on the fan, cut the foliage in the shape of a triangle and trim off long roots.
Divide and transplant iris after they bloom. Bearded iris grow from underground stems called rhizomes. The stringy roots arise from these fleshy stems. Replant rhizomes immediately so the roots keep growing. The plants then have a better chance of blooming the next year.
“To replant iris, dig a hole deep enough so that the top of the rhizome will be just an inch beneath the soil surface. Dig a narrow trench on either side of the center hole in which you will place the roots which remain — solely for purposes of stability.
Add a liquid fertilizer such to stimulate growth, cover with soil and tamp down firmly so that no air remains to encourage rot. Water frequently until the plants are established. This is evident when one of the cut fans shows a leaf growing taller than the others.
Feed your iris after they finish blooming. Add a light dose of fertilizer in March but do not overdo it.
The Utah Iris Society Spring Show is May 24, 2003 from1-5 p.m. from 10a.m. to 5 p.m. at the Sugarhouse Garden Club Center, 1650 East 2100