ShareThisBearded irises can be among the most rewarding -- and frustrating -- flowers to grow. They're mostly easy to care for, but they can baffle even expert gardeners with their unusual habits.
Here are some common questions and advice:
Q. Do bearded iris need a lot of water?
A. No. Water twice a week in spring, then cut back in summer to once a week (or less) as the plants go dormant. In the fall with new growth, resume regular watering, but don't overdo it. Remember: They need good drainage and hate soggy feet.
Q. When should I cut back iris leaves?
A. Green iris leaves should never be cut unless you're digging up and dividing plants, a process that needs to be done every two to three years, usually in late summer when the leaves die back.
Cutting the leaves can prevent the rhizome from growing to maturity and cause the blooms to fail the next year. It's OK, to trim back brown leaf tips on green leaves. Remove brown or dead leaves, usually in late summer or early fall.
Q. Why did my iris stop blooming?
A. Irises grow from rhizomes, a sort of gnarly tuber that is actually a thick underground stem. New blooms come from new growth on those stems or its branches. Unless the rhizomes are divided every two or three years, they get overcrowded with no room for new growth.
Too much shade will stop blooms. Irises can tolerate some shade, but need at least half a day of sun.
If bearded irises are transplanted at any time but late summer, the roots may die. No roots, no new growth, no blooms. And cutting back the leaves cuts back on blossoms.
Q. Why do iris plants change color?
A. It's an illusion. The different-colored iris is actually a new plant sprouted from seed.
Sacramento, Calif., iris expert Wayland Rudkin noted: "One of the pleasures of growing iris is watching the new plants grow after the mother plant has bloomed. I explain to people when they are buying iris that once the plant has bloomed it will never bloom again. However, you will have three or more new plants on the way."
Bees pollinate a mother plant, which drops its seed at its base. The new plant takes only two years to bloom and may be very different from its parent. But these ungrateful children tend to choke out the mother plant with their rapid growth. They only give the impression that the irises changed color.
Antique iris varieties have been known to produce the same color consistently for more than 100 years.
Q. How often should irises be fertilized?
A. Bearded irises have a big appetite. They prefer a balanced fertilizer (such as 6-6-6 or 15-15-15) three times a year: When transplanting, usually in August or September; in February, before spring bloom; and right after they finish blooming in May.
Never use a high-nitrogen fertilizer. (It produces lots of leaves but no flowers and roots.) Many iris growers recommend using rose food or bone meal, a mixture of crushed and coarsely ground bones.
Late-spring feeding gives them a pick-me-up to encourage new growth that will produce next season's flowers.
"If you want to bring out the best the flower has to offer, feed the plants right after blooming," Rudkin said.
Q. How do I plant bearded iris?
A. Irises are not too picky about soil, but they need good drainage and prefer a sunny location. Cut off decayed or broken parts of the rhizome. Plant them shallow with the top of the rhizomes at soil level or just showing and the roots fanned evenly. Keep the soil somewhat moist for the first three weeks while the iris is establishing its roots.
Carefully lift or dig up the clump; a spading fork works better than a shovel. Note that you'll have many more iris than when you started.
Wash soil from the rhizomes. Discard the old decayed rhizomes from the center. With a sharp knife, cut sections of new rhizome showing one or two fans of leaves. Trim the leaves into an even fan shape about 4 to 6 inches tall. Replant the rhizomes.
Rudkin also had this suggestion: "One year, we were able to get a supply of composted (chicken) manure. I dug trenches a foot deep and put in 3 inches of the manure. After filling up the trench, I planted my iris. That year, we had the most amazing bloom ever. Iris are heavy feeders. A little effort can produce big results."
For more information on irises, see the official Web site of American Iris Society, www.irises.org.
The difference between rhizomes and bulbs:
Although some iris species grow from bulbs, the bearded iris grows from rhizomes (pronounced RYE-zomes), a gnarly, tuberlike root that's actually a jointed underground stem.
It looks very different from a typical bulb such as a gladiolus, where new growth sprouts up from one point in the center. Instead, rhizomes grow horizontally just below the soil surface, sending out green growth from several nodes. The name comes from the Greek word "rhizoma," meaning "mass of roots."
(Distributed by Scripps Howard News Service, www.scrippsnews.com.)
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