The general garden culture of Louisiana irises is relatively simple. While these irises have a few preferences, they are not difficult to satisfy. For a longer narrative, click the button. And look for additional references below.
There are almost no diseases affecting Louisiana irises along the Gulf Coast. The most serious is rust fungus. Click below for more information.
Rust appears as red to dark-brown powdery spots on leaves and stems, often surrounded by a yellow margin. Leaves may become severely discolored and die back. The rust does not appear to damage the plants severely, but it does make the beds look bad. Furthermore, the fungus will spread to initially uninfected foliage and can persist from year to year.
The best solution is to remove all yellow, brown, or decaying foliage in late summer or fall. If infected foliage is eliminated instead of allowed to decompose, the cycle can be broken and a garden can be rust free. If it pops up again from time to time, remove infected foliage immediately and dispose of offsite. For an article dealing with iris rust, see the section at the bottom of the page.
Leaf Miner is indicated by long white steaks in the leaves, particularly near the base, in hot weather. The larva of a type of fly causes it. The outermost leaves may collapse and, if they become unsightly, can simply be removed. Leaf miners rarely cause enough trouble to warrant treatment with an insecticide.
Iris borer may be a problem now and then in the Gulf South, but it is far more serious in the north and areas where bearded irises are grown. After traveling down the leaves, the worm enters the rhizome at the tip and may hollow it out, killing it or destroying its ability to produce a bloom stalk. The first sign of a borer may be a center leaf in a fan that turns yellow and dies. This stage indicates that the borer, first deposited on the leaves, has worked down to near the growing tip of the rhizome, which it will devour. If one watches for center leaf damage, the borer can sometimes be found and destroyed before the rhizome is seriously injured. Chewed or damaged foliage may be evident before the borer reaches the rhizome. Sometimes, it is possible to gently spread the leaves of a fan and kill the critter before it does real damage. A rhizome damaged by a borer often produces offsets unaffected by the problem, so discarding the entire plant is unnecessary.
Sunscald is not a disease but a condition resulting from exposed rhizomes scorched by the sun in midsummer, causing them to become mushy and deteriorate. Louisiana iris rhizomes do not naturally grow along the top of the soil but usually just below the soil level. Sometimes, particularly late in the season, the top of the rhizome may be exposed. Adding soil or a mulch solves this problem.
Cutworms are sometimes a problem. Cutworms are chewing insects that will sever leaves and disrupt growth. One recommendation is a fertilizer fortified with an insecticide, such as that sold to control lawn chinch bugs.
Snails and slugs may climb up the bloom stalks and disfigure a flower, particularly under high humidity and rainy conditions. Some growers use commercial snail bait or set out saucers of beer. Snails are not a sufficiently severe problem that most growers do anything about. Those who grow irises for entry in shows may be the exception.
Moles and voles are serious problems in some areas. Some growers have reported growing Louisianas in containers sunk in the ground to prevent the rhizomes from being eaten. Obstructed drainage in the container offers the added advantage of promoting the availability of constant moisture. This tactic is more work than just digging a hole in a garden bed and planting an iris, and if the container is not sufficiently wide, the irises will soon escape as the rhizomes grow longer.
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