Growing Tips for AIS Region 23

BEARDED IRIS CARE, PLANTING, AND CULTURAL INFORMATION

When to Plant:	For best results in New Mexico, Tall Bearded Irises should be planted in late June, July, August or September, three to four weeks after bloom. (September is a little late for the good bloom the following spring, however, in southern New Mexico, digging and planting in September and October seems fine). It is imperative that the roots of newly planted Irises be well established before winter, when the growing season ends.
When to Divide:	For best results, divide iris during the months of June through September, to coincide with planting time. Clumps of iris that are overcrowded, and not blooming well, generally clumps that are 3-4 years old, are good candidates for division.
Where to Plant:	Irises need at least a half day of sun in order to bloom. If your Irises are growing well, but are not blooming, there is a very good chance that they are not getting enough exposure to the sun. They may also be overcrowded an in need of division. Be sure to provide your Irises with good drainage by planting on a slope or in raised beds. If a Bearded Iris rhizome sits in water for more than a couple days, it may rot. In New Mexico, heat can bake the rhizomes and stress the iris. Overwatering at this point without good drainage can lead to rot. Good drainage is very important. Many Bearded Irises are lost in the spring when the snow and ice melts and there is water standing on the ground, and in the summer months due to heat stress and poor drainage. The ideal location for iris is a sunny, well-drained area. Sun should be present for at least 6 hours. Iris do not do well in deep shade. Bearded iris will not tolerate wet feet. No water should stand in the iris beds. Raise the beds slightly above the level of the garden paths, if necessary, to allow for good drainage.
Planting Depth:	Bearded Irises should be planted so the tops of the rhizomes are exposed to feel the warmth of the sun. Planting just below the soil surface is fine, while the roots are just beneath the soil. .Mound the soil in the bottom of the hole and place the rhizome on the mound with the roots flowing unbent over the sides spread out, facing down, where they will enjoy the damp (not soggy) soil. Firm the soil around each rhizome and then water to help settle the soil. A common mistake is to plant bearded Irises too deeply. Deep planting will lead to rot.
Distance between plants:	Generally, iris are planted from 14-18" apart to allow for growth and expansion. If you want an immediate clump effect, you can plant the iris 8" apart in groups of 3 or more of one variety. By planting iris closer together, you may have to divide your plantings more often, but you will have a wonderful splash of color sooner than if you planted only one rhizome of one variety.
Fertilizing:	Iris will thrive without feeding, but will reward you for its application. In the preparation of a new iris bed, mix a good application of compost below the roots. Add bone meal or a small amount of super phosphate to the soil prior to planting the rhizomes and mix in well. You may apply a good fertilizer prior to bloom season, but use a formula of 5-10-10, or 5-10-5. If the nitrogen is too high, the plant will provide many leaves, but little bloom, and may develop soft, lush growth that is susceptible to rot.. Fertilizer should be applied as a side dressing in early spring, and again in the fall. Care should be taken when applying the fertilizer, because it can burn leaves and rhizomes, and should be applied around the plant, not on it. Too much nitrogen promotes soft, lush growth that is susceptible to rot. The same formula of 5-10-5/ 5-10-10 or similar formula is best to apply for spring and fall feeding.
Cultivating and Weeding:	Cultivate shallow. Iris feeding roots are very near the surface. Keep iris free of weeds and do not allow neighboring plants to encroach upon them. Remember, they need sunlight down to the rhizome. Keep grass, weeds, etc. away from the rhizomes. Brown leaves can be trimmed off at any time. Clean cultivation is the finest precaution for iris disease and pests.
Dividing:	When dividing, dig the plant up (a garden fork is the best tool) . Each division should have one or more sections approximately two to six inches with leaves and healthy white roots. Remove and discard the old center rhizomes plus anything that may have rotted or been attacked by pests. You may cut the old centers with a knife while they are in the ground if you do not want to lift the whole plant. If you have never divided iris before, take a look at the article from Region 18 called Bearded Iris Culture , which shows pictures of dividing and planting iris. Another web page to look at for help in dividing iris is: Dividing Iris, which is shows dividing and planting iris.
Soil Preparation:	Irises will thrive in most well drained soils. The soil should be worked to a depth of ten inches. If your soil is heavy, coarse sand or humus can be added to help drainage. Gypsum is a good soil conditioner that can improve most clay soils. The ideal pH is 6.8 (slightly acid), but bearded irises are tolerant in this regard. To adjust the pH of your soil, lime can be added to acidic soils or sulfur to alkaline soils. It is best to have your soil analyzed before taking corrective measures. Soil in New Mexico tends to be toward the alkaline side.
Care of Plants:	Care of plants is relatively simple. Keep weeds and grass out of the iris beds. Cultivate shallow, since the feeder roots are near the surface. Newly set plants should be kept moist until the roots are growing well. Established plants rarely need watering except during prolonged dry spells; at such times, deep, infrequent watering is best. (Iris are good candidates for low water planting in New Mexico.) Air circulation and sanitation are the best problem preventatives. Remove old (dead) iris leaves and other debris from around the base of the plant. Aphids, caterpillars, etc., may damage the flowers, but rarely do serious harm to the plants. Slugs love to nibble at the young shoots and will even climb and attack the tall leaves of some varieties . In some years (usually, a warm wet spring or summer) leaf spot, caused by fungi can make the leaves look unsightly. We usually do not see this much of this in New Mexico. Cutting off the spotted leaves will improve the appearance of the garden and retard the spread of the disease. Discard the cuttings away from your garden. Even though New Mexico climate is hot and dry, some fungus can still occur. Bearded irises may be sprayed along with roses and other perennials with a fungicide spray peridically during the growth period. Old bloom stalks should be broken off at ground level but healthy, green foliage should NOT be cut off. The foliage should be left on the rhizomes, which promotes the development of the new sprouts for the next season.
Links to Other Iris Cultivation Information:	Bearded Iris Culture is an article from Region 18. This article contains some very good pictures showing division and planting of iris. It is very helpful!

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Last Update: March 18, 2011