The Louisiana Iris (like Sinfonietta pictured left) is a native to the southeastern United States. Aptly named for its region of origin, this species grows in the swamps, along riversides, and damp hillsides. Garden cultivation and hybridizing of the Louisiana Iris has brought us a vast array of colors and flower forms.
Louisiana Iris grow well in much of the world, proving highly adaptable as to climates, soils, and cultural practices. Despite the common perception that Louisiana Iris must be grown in bogs or water gardens, they will tolerate a wide range of moisture conditions. While they will usually survive a periodic drying out, they will not prosper nor bloom well if grown with less than an inch of water per week during the growing season. Here is a link to an interesting article from the blog "World of Irises" about growing Louisiana Iris successfully in northern states.
Here we provide a further guidelines on growing and caring for your Louisiana Iris.
When you receive your rhizomes, soak them in water overnight before planting. Keep the tops of the rhizomes one inch below soil level. Use a general fertilizer such as 10-20-10. After planting keep them moist, not allowing the rhizomes to dry out. In warmer climes these tough Iris can be planted at just about any time, assuming you provide adequate water and protection from the hot sun. In colder regions of North America they should be planted early enough in the autumn so the roots can get established before the onset of cold weather.
Like most Iris, Louisianas need sunlight in order to prosper. They bloom best with six to eight hours of sunlight per day. In hot climates, and in the desert southwest, afternoon shade would be good. If you have a low area in your garden where water stands for long periods, you probably have a good place to grow Louisiana irises—assuming you have adequate sunlight.
Louisiana Iris tolerate a wide range of soil types and acidity levels. The old belief that these irises preferred a highly acidic soil has been disproved. The best advice is to avoid both pH extremes.
Louisiana Iris evolved in the lowlands of the southern Mississippi delta, and thus they tolerate heavy clay soils. Indeed, clay soils retain moisture over a long period, which Louisianas love. These Iris will also grow well in a soil with high organic matter content, as long as it is moist; they suffer considerably when growing in sandy soils unless copious amounts of organic matter are added.
Louisiana Iris grow quite well in beds that have been lined with plastic. Such beds should be at least six inches deep.
~Culture information adapted from The Society for Louisiana Irises
For new or replanted beds (to which commercial fertilizer and organic material have been added at planting time), a light dressing of a complete fertilizer (2-4 lbs. Per 100 square feet) is sufficient about two months prior to bloom (late January in Louisiana). Beds which have not been replanted in late summer are generally given two applications, a fairly heavy application at the start of the growing season (with good watering in), and then the light dressing just before bloom. Complete fertilizers such as 8-8-8 are preferable to high nitrogen fertilizers. High nitrogen can cause the plants to produce leafy growth while suppressing flowering; it can also make the plants more susceptible to disease.
~The above information adapted from The Society for Louisiana Iris website
The best time to plant and divide Louisiana Iris is mid-to-late August and September. Transplanting immediately after blooming is not recommended. If existing beds are to be divided and replanted, dig out all the Iris and rework the beds, adding organic materials and a commercial fertilizer. Replant as soon as possible, preferably the same day. Do not allow the newly planted beds to dry out; water every few days until the plants are established. Planted in a triangular format (about 12 inches apart), they can be left 3 to 4 years and will form nice clumps.
Iris grow in the direction they face; at least two offsets generally form each year, one on each side of the rhizome. Each rhizome blooms only once, then the offsets bloom the next year. Good growth and offset formation are, therefore, necessary each season for consistent bloom. The offsets represent vegetative reproduction and are identical in every respect to the parent rhizome.
~The above culture information adapted from The Society for Louisiana Iris website
While Louisiana Iris will tolerate moderately dry conditions for short periods of time, they should never be allowed to dry out completely. Upon being planted, young rhizomes need to be kept constantly moist for at least one week. Once established they will grow and bloom in a normal perennial bed or border. These Iris respond well to deep watering rather than a mere “sprinkling.” Drip irrigation can be very effective.
Louisiana Iris will always produce best if given lots of water. They will even grow and bloom in standing water. They are ideal for growing in pots sunken into fishponds.
Obviously, Iris growing in standing water will need more attention to feeding than ones planted in soil. The standing water can dissolve nutrients quickly, requiring more frequent feedings.
Given their preference for even moisture, Louisiana Iris respond well to being mulched. Mulching has the added advantage of regulating fluctuations in soil temperature, and it also protects the rhizomes (which often grow right at the top of the soil line) from the dreaded sunscald and the extreme temperatures. Importantly, good mulch will deter weeds from invading your growing area.
Many long time growers of Louisiana Iris use pine needles (known as “pine straw”) to mulch their beds. They are long lasting and do not mat down. Leaf mold makes great mulch. Avoid mulches of heavy woody material as it might take nitrogen from you soil during the decomposition process. Be forewarned that hay might make good mulch, but it usually contains weed seeds.
In hot climates Louisiana Iris rhizomes are subject to sunscald, a common problem which can result in poor bloom, rot, and other afflictions.