Louisiana Iris Growing Tips

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Location

Provide at least a half day of sun. Unless the irises are growing in water, a little shade is a good thing in hot areas. In the cold North where the growing season is shorter, full sun is essential for goog bloom.
Avoid tree roots to the extent possible
Regular beds are fine; boggy conditions are great but not necessary
Be able to provide consistent moisture. If the irises are exposed to a summer dry spell without consistent watering, they will tend to go dormant, and, at least, the foliage may not look good until fall.

Dig in several inches of compost or other organic material (e.g., finely ground bark or peat moss).
If preparing the beds several weeks in advance, work in chemical or organic fertilizer (equivalent of 1 lb. of 8-8-8 per 10 square feet of iris beds; if planting irises immediately, apply the fertilizer as a top dressing after the irises are planted.
An acid to slightly alkaline soil is fine. Louisiana soils are generally good for Louisiana irises, and pH is not an issue.

Space irises with room to "walk" in the direction in which the leaves are growing from the rhizome and 6"-9" apart in a triangular pattern.
Plant with the rhizome just covered with soil, 1/2 to 3/4 inches. No more than 1 inch.
Mulch after planting, e.g., with 2-3 inches of ground bark, leaves, pine straw or equivalent materials.

Fertilize established beds in September or October and again in late February or March. Many recommend a third dose after bloom. These dates are for the Gulf Coast with bloom expected from late March through April and foliage growth continuing through the winter. Adjust for climate, especially in areas with significant snow cover in winter.
In the Fall, use 1 lb or 8-8-8, or equivalent, per 10 sq ft of iris bed. In the Spring, use the same amount, or a bit less.
Regularly remove and discard any foliage that yellows. Don't compost the yellowed foliage since it can harbor rust spores.
Keep the beds consistently moist. If the irises get too dry, they will cease growing and the foliage will not be attractive. The plants will resume growing in the fall, however.
Remove bloom stalks after the bloom season unless you want to harvest seeds in late June or early July. Cut stalks to within an inch or so of the ground.
If the stalks are not removed, at least remove any seed pods before summer to avoid unwanted seedlings popping up among existing plants.
Divide irises after 3-5 years or if they lose vigor. Replenish soil as if creating a new bed.

The LSU AgCenter Research and Extension division offers a good brochure on Louisiana iris culture that is available online.