LOUISIANA IRIS SOCIETY
Although originating in wetlands of the Deep South, these versatile iris do not require aquatic culture.
Louisiana iris can thrive in typical garden beds, along with ponds and bogs. To continue to stay green and grow, they need only adequate moisture during dry spells and drought.
For lush blooming, keep them away from trees or plants with extensive root systems and make sure they get at about ½ day of sunshine. Less sunlight will diminish bloom. If planted in full sun, they need to be planted in water.
Louisiana iris can be grown alone in a bed, or along with small annual plants. Iris only beds will go through a cycle after blooming where yellowing foliage may be unattractive. This yellowed foliage will need cutting back to keep the beds neat, and to encourage the new growth cycle in the fall.
Louisiana Irises prefer acid soil but this is not necessary. They have been found growing well in wetlands that are acid, but also around New Orleans and the Mississippi River flood plain where the soil may be neutral or a bit alkaline. In other words, they will grow in most any natural soil condition other than very alkaline soil. Soils in the PH 6.5 to just over 7.2 range have produced excellent results.
In preparing your beds, iris does require high fertility. Organic materials such as finely ground pine bark, composted oak and other leaves or rotted manure, are excellent additions that should be worked into the soil when beds are made. These will help the soil maintain moisture.
Heavy clay garden soils can be improved by adding some sand to loosen the texture. In bogs, clay alone is fine. Adding organic matter or sand to garden soils helps produce a loose, friable soil that helps promote growth and bloom.
If growing in a container in water, the soil mix needs to be heavy enough to keep the plants from floating out of the container, and also to provide stability in wind. There is a a wide variety of soil types that seem to work well, from nearly soil-less mixes to good garden dirt.
If you can, prepare your beds a few weeks before planting. The typical recommendation is to add 2-3 inches of organic material and a generous amount of commercial fertilizer such as 8-10 lbs. per 100 sq. feet of 8-8-8 to the bed to the bed and work it in. Azalea/camellia fertilizer works well in excessively alkaline soil. Organic fertilizers are also effective, but to equate the amount equal to chemical fertilizer is difficult.
Planting and Dividing
The growth cycle of Louisiana irises in their native range begins in the fall. As opposed to most plants which begin new growth in spring, growth continues through winter and finishes with a burst of rapid growth and bloom in the spring. New growth is often indicated by the swords gathering up like ribbon that is pushed together. Extreme heat will slow or even stop the growth if there is not enough water or moisture during those times. The north may not experience this growth as snow and cold will interrupt the growth cycle. Bloom season along the Gulf Coast may begin in mid-March, whereas bloom may start in mid to late June farther north.
When to plant
Mid-to-late August, September and October, after the period of new growth has begun is the optimal time to divide and replant beardless iris like Louisiana's. Irises planted later than November are not likely to become well enough established to reach normal size and bloom in the spring. In cold climates, planting needs to take place early enough for roots to establish before the coldest weather sets in.
August and September are the preferred months for this. Planting during the heat of summer will stress the plants, and little growth or even an early dormant period may result if not kept watered. The longer into the season foliage growth can be continued, the better the chances of good bloom the next year, If it is necessary to transplant after bloom, be sure to supply extra water. If you cannot plant when receiving your iris, hold the irises over in pots set in shallow water and partial shade, until new growth has resumed and plant in fall. Growers in such warm climates in South Florida report that Louisiana iris can be divided at any time of the year.
How to Plant
Iris should be planted about 12 inches apart to allow for spread. Irises rhizomes should be completely covered with 1-2 inches of soil and have 1-2 inches of mulch over the soil. Louisiana irises form clumps that can be left in place 3-4 years before needing dividing. At that time, it is helpful to dig and divide the irises, thinning them out and replenishing the soil with organic matter as if preparing new beds.
If you plant your rhizomes too close together, they will grow across one another and be difficult to identify. How fast they spread depends on the particular variety. The size of different rhizome varieties are not all the same. Each plant can produce two or more offsets each year on either side of the rhizome, and extend perpendicular to the mother rhizome, which eventually produces a clump. Each rhizome blooms only once, followed by offset bloom in subsequent years. Keep this grown pattern in mind when deciding how to lay out your beds. Divisions will reproduce flowers identical to the mother plant, while seeds may produce various different color and shape flowers due to cross pollination by insects and wind.
The beds should not be allowed to dry out. During dry spells, give the iris beds a thorough soaking at least once weekly. Failure to do so may cause growth to halt or cause the plant to go dormant.
Fertilizing recommendations vary among Louisiana iris growers. For new or replanted beds, a light dressing of 6-8-8 or 8-8-8 is sufficient about two months prior to bloom. Established beds are generally given a fairly heavy one at the start of the growing season, and then the light dressing just before bloom. High nitrogen fertilizers are not recommended as they can bring on excess plant foliage, reduce bloom, and possibly make the plant more susceptible to disease. Some growers recommend a third feeding after bloom. You can also use liquid fertilizers or timed-release products such as Osmocote, especially in water culture.
Louisiana irises are heavy feeders, and some average gardeners fertilize them a good bit less than optimal. Failure to water properly or give proper nutrition will cause yellowing during the hot months. Problems from over-fertilizing are rare, but failure to produce bloom is often associated to little water and failure to fertilize.
Mulches help with maintaining soil moisture, keeping weeds under control, increasing organic matter in the soil and protects against sun scald on exposed rhizomes. Excellent mulches are fresh or rotted leaves, pine needles or pine bark.