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How to Grow and Care for Iris
Iris are hardy perennials that are easy to grow and care for in the right kind of environment. Tall Bearded Iris grow well in northern temperate zones. Here we have provided a primer on how to establish your Iris once you receive them, how to care for them, blooming, and how to troubleshoot problems your plants may have. To read fascinating details about the Iris, see Wikipedia's Iris page and to read more about classifications, visit the American Iris Society's site.
When to Plant For best results, Iris should be planted in July, August or September. It's imperative that the roots of newly planted Iris be well-established before the growing season ends. In areas with hot summers and mild winters, September or October planting may be preferred. Where to Plant Iris need at least a half day of sun. In extremely hot climates, some shade is beneficial, but in most climates Iris do best in full sun. Be sure to provide your Iris good drainage, planting either on a slope or in raised beds. Soil Preparation 
Iris will thrive in most well-drained garden soils. Planting on a slope or in raised beds helps ensure good drainage. If your soil is heavy, coarse sand or humus may be added to improve drainage. Gypsum is an excellent soil conditioner that can improve most clay soils. The ideal pH is 6.8 (slightly acidic), but Iris are tolerant in this regard. To adjust the pH of your soil, lime may be added to acidic soils or sulfur to alkaline soils. It is always best to have your soil analyzed before taking corrective measures.
Iris should be planted so the tops of the rhizomes are exposed and the roots are spread out facing downward in the soil. In very light soils or in extremely hot climates, covering the rhizome with 1 inch of soil may be desirable. Firm the soil around each rhizome and then water to help settle the soil. A common mistake is to plant Iris too deeply. Distance Apart 
Iris are generally planted 12 to 24 inches apart. Close planting gives an immediate effect, but closely planted Iris will need to be thinned often. Plants spaced further apart will need less frequent thinning. Watering Newly set plants need moisture to help their root systems become established. Specific watering information depends on your climate and your soil, but keep in mind that deep watering at long intervals is better than more frequent shallow waterings. Once established, Iris normally don't need to be watered except in arid areas. Overwatering is a common error. Fertilization Specific fertilizer recommendations depend on your soil type, but bone meal, superphosphate and 6-10-10 are all effective. A light application in the early spring and a second light application about a month after bloom will reward you with good growth and bloom. Avoid using anything high in nitrogen, as nitrogen encourages rot problems. Thinning Old Clumps Iris need to be thinned or divided before they become overcrowded, generally every 3-4 years. If Iris are allowed to become too crowded the bloom will suffer, some varieties may crowd others out and disease problems may be aggravated. Old clumps may be thinned by removing the old divisions at the centers of the clumps and leaving new growth in the ground. Or, you may dig up the entire clump and remove and replant the large new rhizomes. General Garden Care Keep your Iris beds clean and free of weeds and debris, allowing the tops of the rhizomes to bask in the sun. Bloom stems should be cut off close to the ground after blooming. Healthy green leaves should be left undisturbed, but diseased or brown leaves should be removed. Growing Iris In Pots
Iris can be successfully grown in pots. First, select a roomy pot. A 6" to 8" pot will work for Dwarf Iris; a 12" pot will work for Tall Bearded Iris. Make sure your pot has good drainage. For soil, we recommend 45% fir bark, 20% pumice, and 35% peat moss. Leave at least one inch below the pot's rim, and leave the top of the rhizome exposed. Water only when the top two inches of soil are dry. Overwatering will cause rot. Keep the pot outdoors during the winter. When bloom buds begin to appear in the fans, bring the pot inside and place in a bright sunny window. After bloom, be sure to divide your Iris and replant outside or into more pots.
When do Iris bloom? Tall Bearded Iris bloom in the spring for 3-4 weeks. Our bloom season here in Oregon generally runs from about May 1 to June 6, depending on the weather. Our peak bloom is normally May 20th to the 30th. The Dwarf Iris bloom earlier, in mid April. Do Iris bloom only in the spring? Several varieties have been known to rebloom after the initial spring bloom season (usually 4-8 weeks after initial bloom). Subsequent blooms are not as reliable as the initial bloom, depending on the quality of the soil, climate, and geographic location. Remontancy is not guaranteed. We offer a special collection that features reblooming Iris. How can I extend the life of my blooms as cut flowers? For longer lasting flowers cut your Iris early in the day with the buds just opening. Place them in a bucket of tepid water and recut the stem end underwater at an angle one inch up. Display your Iris in a cool niche away from direct sun and drafts. Pinch off and remove wilted flowers immediately. Check the water level every other day and replenish as needed. I love Iris, but their bloom season is just too short. Any ideas? An Iris clump should bloom for about two weeks. There are some Tall Bearded Iris that bloom early and some that bloom late, so try some of each to lengthen your season by a week or two. Consider some of the smaller bearded Iris, such as the Intermediate and Standard Dwarf Bearded Iris, as you can add a month to the beginning of your bloom season using these. And finally, consider the reblooming Iris, which can give bloom in the summer and fall.
Do my Iris need watering? Iris initially need water after they have been planted and throughout the first growing season to help their root systems become established. Established Iris will benefit from watering in the spring, but need no other watering in most climates. Infrequent deep watering is much better than frequent shallow watering. It is always better to under water than over water.
What kind of fertilizer should I use? One month before bloom season, while the tulips are blooming, apply a low-nitrogen, well-balanced fertilizer, such as 5-10-10 or 6-10-10. Keep the fertilizer several inches away from the rhizomes. In late September, fertilize again with bone meal.
To ensure a good bloom, we recommend thinning iris clumps every three or four years. In the late summer, dig up the clump, separate the new rhizomes, and replant.
Always keep your Iris beds clean and free of weeds. After they bloom, cut off bloom stems close to the ground. Watch for diseased or dying leaves, and remove them immediately. In the late fall or early winter, cut healthy leaves back to about six inches.
Do my Iris need winter protection? We recommend covering newly planted Iris, especially in areas with cold winters. Soil, straw, pine needles, and leaves are all effective covers. Remove the cover as early as possible in the spring. Early planting will also help your Iris become established before the first winter.
Are there any weed-killers compatible with Iris? Unfortunately, there is no one chemical that will kill all weeds and not also harm your Iris. There are herbicides that will kill grasses while not harming the Iris. There are also pre-emergent herbicides that will keep weed seeds from germinating while not harming the Iris. Avoid using mulches, ground covers, or man-made weed barriers to control weeds around your Iris. If you cover your Iris with any of these, the Iris may quickly rot. There is really no substitute for hand weeding!
How can I tell if I have Iris borers? What should I do about Iris borer? 
Fortunately, we do not have Iris borers in the west. However, the Iris borer can pose a very difficult problem in the Midwest and along the east coast. They hatch in the spring and chew into the leaves, leaving chew marks on the margins of the leaves. They then bore down through the leaf, leaving long wet looking streaks on the leaves. Once they get into the rhizomes, they gorge themselves. What they don't eat then can rot. First, always maintain a clean garden. If you see the borers in the leaves, simply squash them. We recommend using the insecticide Cygon 2-E. Spray in two week intervals from about the time the tulips bloom through mid-summer. A 10% solution of Murphy's Oil Soap (one part soap for every nine parts water) can be used as an organic alternative to Cygon. My leaves have yellow and brown spots. What should I do? 
Excessive moisture and rainy or humid weather can lead to this problem known as leaf spot. Always remove old dead leaves, and cut off and destroy any leaf or part of a leaf that is affected. In the spring, about six weeks before bloom, begin a regular spraying program with a fungicide. Using two fungicides alternately is often more effective than using one exclusively. What should I do about slugs, snails, and other pests? In early spring, or when you notice damage from slugs and snails, bait for these pests using whatever method you prefer. Aphids, thrips, and whiteflies can be controlled by an insecticide such as Cygon 2-E or Malathion. Insecticidal soaps can also be effective. What should I do to control soft, smelly rot? Excessive moisture can sometimes lead to outbreaks of bacterial rot. It is imperative that you remove the rotting tissue as soon as possible. Remove the soil from around the rhizome, leaving the roots anchoring the plant. Using an old spoon, carefully scoop out all the mushy tissue. If necessary, dig up the entire plant and remove the rotten tissue. After removing the tissue, drench the wounds with a 10% bleach solution (1 part bleach to 9 parts water) and allow them to dry for several days before covering with soil again. My Iris aren't blooming. What can I do? For Iris to bloom consistently, they need full sun, good drainage, lots of space, and quality soil. To improve your chances of bloom, add fertilizer and divide large clumps. Only 60-75% of Iris bloom the first year after planting. Sometimes they need an extra year to become established. Unusual weather conditions or late spring frosts can also harm bloom. Do Iris change color? We have grown Iris since 1925 and have never seen an Iris change color. Iris do not change color - it's simply a genetic impossibility. If your Iris are blooming in colors different than you'd expect, what is more likely to have happened is that your Iris are overcrowded. More vigorous varieties will tend to crowd out the less vigorous varieties. Give your Iris lots of space, and divide them every three or four years. When you divide them, be sure to dig up the entire clump, not leaving behind any new shoots that might get mixed in with your new varieties. Another possible explanation is that a chemical drift from a chemical spray (such as the weed killer Roundup) affected your Iris, possibly warping and damaging the flower and its color. My Iris look healthy and produced stems, but the buds never opened. What happened? Your Iris are growing very quickly in the spring before bloom. This new growth is very tender. A cold night can abort the growth of the bloom buds. My Iris leaves are wrinkled up. Why? Sometimes an Iris fan will have stunted growth and the foliage will appear like corrugated cardboard. This is called "pineappling." No one knows the exact cause of pineappling, but though unsightly, the plant will not be lost. It is not a contagious disease. Such abnormal growth is probably due to unusual weather conditions. Normally, the side increases will grow fine and not be affected. Why don't all my Iris grow the same? Each Iris variety has its own personality. Genes control the color of our hair or eyes, and likewise play an important part in Iris growth. Some Iris are very vigorous and increase rapidly. Others grow more slowly, are shorter, and have less disease resistance.
How should I plant my Louisiana Iris? Plant your Louisiana Iris in full sun. They grow best in acidic soil (pH 6.5) that is prepared with lots of organic matter, humus, and compost. Good drainage is not necessary, as these Iris do well in mud and water. These plants can be planted at any time, but we suggest planting in August and September. When you receive your rhizomes, soak them in water overnight before planting. Keep the tops of the rhizomes one inch below soil level. Use a general fertilizer such as 10-20-10. After planting keep them moist, not allowing the rhizomes to dry out. How do I transplant my Louisiana Iris? Select a location that will allow for three year's increase. Leave about 12" between rhizomes. Keep Louisiana Iris moist between digging and transplanting. How should I care for my established Louisiana Iris? Keep the soil well fertilized. Use manure or compost, or add a side dressing of artificial fertilizer in the spring and fall. Water regularly, but Louisiana Iris do better with more than average water. Use a layer of mulch in the summer, especially in hot, dry climates, to prevent the soil from drying out. Cut back dead and decaying foliage in the late fall. In cold areas, put a thick mulch of straw or leaves around the rhizomes during the winter. Be sure to remove the mulch in early spring.
How should I plant my Siberian Iris? Upon receipt, soak your rhizomes in water overnight. Plant your Siberian Iris deeper than other Iris, covering the rhizomes with one or two inches of soil. Space your plants two feet apart. Use acidic soil (pH 5.5 to 6.9). Peat moss, compost, and humus all work as soil enhancers. Plant your Siberian Iris where they will receive full sun. Good drainage is essential, as Siberians thrive in moist but not soggy conditions. How should I care for my Siberian Iris? Keep your rhizomes moist, as they should never be allowed to dry out. Lightly fertilize in the spring and after bloom. We recommend using mulch during the first winter to prevent any damage. When the foliage dies back in the fall, cut it off close to the ground and remove it. |
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3625 Quinaby Road N.E. |
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Depth to Plant
What should I do when my Iris become crowded?
What care do my Iris need once they are established?