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HOW TO GROW IRISES: Bearded Iris Culture

When to Plant or Divide-- For best results in New England, Tall Bearded Irises should be planted or divided in July, August or September, three to four weeks after bloom. (September is a little late in the northern part of the Maine but early to mid September is workable in southern New England.) It is imperative that the roots of newly planted Irises (All kinds) be well established before the growing season ends. That is why the Maine Iris Society holds itís Iris Auction in July and the Connecticut Iris Society holds their auction in early August.

Where To Plant---Irises need at least a half day of sun in order to bloom. In Maine a whole day is best. The most spectacular bloom occurs in full sun. 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. Many Bearded Irises are lost in the spring when the snow and ice melts and there is water standing on the ground.

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 England tends to be toward the acid side.

Depth to Plant--- Bearded Irises should be planted so the tops of the rhizomes are exposed to feel the warmth of the sun while the roots are placed deeper in 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.

Fertilizer ---Fertilizer should be applied as a side dressing in early spring. Fertilizer can burn rhizomes, and should be applied around the plant, not on it. Too much nitrogen promotes soft, lush growth that is susceptible to rot, so a 5-10-5/ 5-10-10 or similar formula is best.

Distance Apart --- Distance apart varies according to the effect desired. Close (8 to 10 inches) for immediate effect. If the plants are 2 feet apart, they will need dividing every 3 to 4 years, more often if they are closer. If you have more than one rhizome of a cultivar, arrange them in a clump with the leaf end facing out. Planting three rhizomes in a triangle of equal sides gives an attractive clump effect.

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.

Care of Plants--- Care of plants is relatively simple. Keep weeds and grass tufts out of the rhizome clumps. 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. 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 warm wet ones leaf spot, caused by fungi can make the leaves look unsightly. 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. Bearded irises may be sprayed along with roses and other perennials with a fungicide spray at regular intervals usually every 10 days to two weeks 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, to foster development of the new sprouts for the next season.

Mulching ---Mulching of bearded irises is to be avoided during the growing season. If you desire to mulch the bed for appearance, you should NOT cover the rhizomes. The sun must reach them to facilitate development of next yearís increase. Freezing weather will not harm the rhizomes, other than causing them to heave out of the ground as a result of successive freezes and thaws. A good remedy for this is to mulch with pine needles or salt grass after the ground has frozen. Evergreen boughs also help. You wait until the ground is frozen to keep the mice from making homes in the soil under the mulch. This provides an insulating affect that prevents the ground from thawing and freezing so much as the weather cycles from cold to warm and back again. In the early spring, usually late March, the mulch must be removed. If any roots have been heaved out of the ground, simply cover them with additional soil. We strongly recommend winter mulching newly planted irises to keep from losing them. The reason for using pine needles or salt grass is that they do not hold water or get soggy. Prolonged wetness on bearded iris rhizomes many times produces rot.

Gardening Tools: Trowel
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