Lousiana irises are derived from four species from the United States of America: Iris fulva, Iris giganticaerulea, Iris brevicaulis and Iris nelsonii. They have large, sumptuous flowers in colours ranging from white, cream, yellows and oranges to reds, pinks, blues and purples.They do well in warm, humid climates such as Sydney, as well as cooler regions! Most will tolerate light frost, especially if they are mulched well in autumn. They need sun but will tolerate filtered sunlight in hotter areas. They demand an acidic soil and plenty of water in their growing season: in fact, they can be grown in boggy soils, ponds or water features. They are also suited to growing in pots. The rhizomes should not be exposed. They need plenty of compost and lots of feeding to give the best results (some growers use a camellia food), and they appreciate an organic mulch to keep them cool in summer.
Because of their vigorous, rapid growth, they need dividing every few years. The best time for this is in March or April. Rust and leaf spot can be problems; treat with an organic fungicide or cut the leaves to the ground around February so new foliage can grow. Snails and slugs can ruin the flowers; use a pet-friendly organic bait or hand-pick and dispose of them. I used to grow a number of these irises; I only have one now, as I found their flowering season quite short. However, I still look forward to the blooming of my remaining plant (pictured above)!