PLANTING

WHEN:
Irises may be planted anytime between July and September. A plant in bloom during May or June is best left undisturbed until its bloom season is over. The rhizomes can be transplanted two weeks after their bloom season. We will give you healthy rhizomes freshly dug from the ground. If you cannot plant your irises as soon as you receive them, store them spread out in a cool, dry place and try to plant them within two weeks' time to ensure their vitality.

WHERE:
Usually irises do best in full sun. Planting on a slope or in a raised bed ensures good drainage. Tall bearded irises, unlike louisianas, do not do well in standing water.

Preparing Soil

Irises do well in most soils, though a pH of 6.8 (slightly acidic) is considered ideal. Lime makes soil more alkaline, and sulfur makes soil more acidic.

Distance

Planting too closely will necessitate frequent thinning. Planting 1 to 2 feet distance apart will allow you to leave iris clumps undisturbed for up to 4 years.

Depth

Only the roots should be embedded in the soil. The rhizome should ride on top of the soil to ensure adequate sun exposure. Soil should be firmed around the rhizome after planting and then watered to help settle the soil.

Watering

Under normal conditions, irises don't need to be watered except for the first two weeks after planting, which helps establish the root structure. Hot, dry climates will naturally necessitate occasional watering. Overwatering over the course of a season is to be avoided as rot can result.

Thinning

The plants will become crowded and diseased and not bloom properly if the clumps are not thinned every 4 to 5 years. You may wish to separate part of the clump or dig the whole plant up and divide the rhizomes, planting them toe to toe with adequate space in between in a circular fashion.

MAINTENANCE

Rid the garden of weeds and debris frequently so the rhizomes can receive the sun. Remove dead and diseased leaves and old bloom stalks. Cutting the leaves back to about 6 inches in summer or fall will help prevent withered leaves covering the rhizomes. Treating your garden with TREFLAN or some other pre-emergent herbicide (available at your local co-op) in early spring and again in the fall will help minimize new weed growth.

Fertilizing

Recommended fertilizers are 6-12-12, bone meal, superphosphate and composted horse manure. Fertilize in the early spring and about a month after bloom season. Avoid fresh manure as it is high in nitrogen and can cause rot.

Pitfalls

ROTTING: Too much moisture can promote bacterial soft rot; so can overfertilizing and insect devastation. Yellowing fans toward the base of the plant are a symptom of a rot problem. The mushy soft rhizome tissue should be removed with a knife or spoon and the wound treated with a disinfectant such as sulfur powder (available at local co-op or garden centers). Avoid letting the scooped-out rot touch any healthy parts of the plant, as this may spread the problem.

IRIS BORERS / other insects: Borers feast on iris leaves, leaving nicks or slimy wet areas on the surface. Often they will hollow out the rhizomes, causing the fans to fall away and rot to spread. Two effective insecticides to use against borers are Cygon 2-E (available at local Co-op) and Bayer Grub Control (available at Lowe's / Home Depot). Spray according to directions in two week intervals from early spring through mid-summer. Spectracide is also good (available at local co-op or garden centers). Catnip planted around the garden helps control some types of aphids and other insects.

LEAF SPOT: This problem is the result of a fungus that is spread by wind and rain. It appears near the tops of leaves as small yellow and brown dots and spreads downward, destroying leaves and sometimes resulting in root rot. It is helpful to remove old dead iris leaves you discover to be infected. Daconil, Bayleton and Captan and other fungicides (available at local Co-op) should be sprayed about six weeks before bloom and after rain. It is better to alternate two different fungicides than to use one exclusively, since the fungus can build up resistance to a given fungicide with repeated use. Putting a teaspoon or two of liquid detergent in the spray mix helps to attach the spray to the leaves.

Winter Protection

Newly planted irises need extra protection during cold winters. Soil may be used to cover the rhizomes as well as pine needles and straw. This should be done in late fall but then removed as the new growth of leaves begins appearing in early spring. However, established irises rarely need winter cover in Middle Tennessee.

Irises are subject to natural hazards and we cannot be responsible for conditions in other gardens. However, following the guidelines on this sheet will greatly aid in the culture of your irises.