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Louisiana Iris

When to Plant:  Plant Louisiana iris in the fall (September) after the temperature has cooled less than 100 degrees and before frost.

Where to Plant:  Plant Louisiana iris in good soil with at least half a day’s shade. Morning sun or filtered sun is acceptable. Good drainage is not required since LA will grow in mud or water. Borders of boards, bricks, or rocks helps hold moisture and mulch materials. Plant rhizomes at or slightly below ground level and shade with a layer of mulch or soil in summer, especially in dry hot climates when planting in full sun. They do fine in the ground, in large pots, and are fantastic when the pots are submerged in a fishpond or other garden water feature.

Soil Preparation:  Prepare beds at least a month in advance. For 100 sp. ft, use 2-3 lbs of treble super phosphate, 3 lbs. Soil sulfur and 2 lbs of nitrogen (ammonium sulphate). If using ammonium phosphate instead of treble super phosphate, skip the ammonium sulphate. The soil sulphur will increase acidity of the alkaline soil. To counteract yellowing leaves, use iron chelate according to package directions. Dig in peat moss, compost, straw and/or rotted manure to loosen soils and hold moisture. Some literature suggests adding clay to better support the heavy foliage system.

Watering:  Water well first before planting the first time and keep bed damp all year long. After bloom season, the plants need to be watered well at least weekly. Water every day if necessary to keep LAs always damp. Soaking the bed is suggested. Growth will slow down in the summer, but the plants should not be allowed to lose their leaves and go dormant. LAs, being native to bogs, like to be continuously wet. LAs have a fondness for moisture and many varieties can tolerate standing water. But the water levels may need to be dropped in the winter because letting the plants freeze in ice during the winter is fatal.

Mulching is absolutely vital to Louisiana Irises that are being grown in garden beds and borders. Mulch at a depth of 3 inches will help to conserve water and protect the rhizomes from sunscald. A mulch depth of 8-10" added before really cold weather set in may be needed in northern areas where freezing weather is expected. Pine needles make excellent mulch, as do well-chopped autumn leaves.

Fertilizing:  Louisianas are heavy feeders. After frost danger is over, start fertilizing. You can use Miracid at ½ rate by sprinkling lightly around each plant or over the complete bed every two weeks up to bloom season and again after bloom season just once. Do not fertilize during the bloom period. Louisiana irises like to feed more during the year than other varieties. Add iron to keep color in the foliage. Established plants should be side dressed in Spring and Fall.

Bloom Season:  Louisiana irises bloom at the same time as the Tall Bearded Iris.

General Garden Care:  Cut spent bloom stalks if not being kept for the seedpods. Remove dead leaves only after they are ready to fall away from the rhizomes. Some varieties stay green all summer and some go completely dormant. Most, if kept well mulched and watered, will remain green all summer. Provide shade over rhizomes in the summer to cut down on sun scald that reduces increase and future bloom.

Moving & Thinning:  Transplant or thin Louisiana iris in September. Wash plants and roots well, place in plastic bags and store in the refrigerator – NOT the freezer. Always keep the roots long and damp. Most clumps need to be divided about every other year for best results. Leave enough space between plants to allow for long rhizomes that "travel" or "walk" as much as a foot from the old rhizome. Cut the foliage back and water to settle the soil around the roots. Pin the rhizomes to the ground when planting in shallow ponds or along creeks.


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