LSU AgCenter Horticulturist
The Louisiana iris (Iris spp.) has been named the spring 2022 Louisiana Super Plant selection by the LSU AgCenter. It comes as no surprise to Louisianians that this native beauty is worthy of this title. No other flower conjures thoughts of Louisiana more than the iris, except maybe the southern magnolia.
This herbaceous, semi-evergreen perennial grows best in full sun but will perform well in partial shade. Blooming begins in late March and continues through May, and flowers come in a wide range of colors including burgundy, blue, lavender, pink, purple, red, white and yellow. Plants actively grow beginning in the fall in October through early summer.
The Louisiana iris has a dormant period at the end of summer in August through October. This is the best time to divide clumps of iris. Overcrowded areas will not be as healthy and can diminish flower production. This iris spreads by rhizomes — continuously growing, horizontal, underground stems that put out shoots and adventitious roots at growing points. These can be cut into individual portions so long as the section has at least one growing point.
Division of clumps should be done during the dormant period in late summer. Divided clumps can be shared with friends and neighbors, relocated to a new location in the garden or planted in containers. Louisiana irises also can be planted successfully in the spring from containers purchased at retail garden centers.
There are five main species of Louisiana iris: Iris fulva, I. brevecaulis, I. hexagonaI, I. nelsonii and I. giganticaerulea. Hundreds of cultivars and hybrid crosses have occurred both naturally and as a result of breeders seeking unique flower colors.
Irises are an excellent selection for low areas that hold water because they are so water tolerant. Additionally, they make a good selection for rain gardens and can be planted along the banks of ponds or lakes to help stabilize the soil. Plants do well also in containers and in raised garden beds.
There are few pest and disease issues associated with the Louisiana iris. The plant disease rust can affect it and typically shows up as tiny red or dark brown spots with yellow margins on the leaves and stems of the plants.
Rust often appears in early summer after flowering has stopped. The disease does not typically kill plants and because it shows up after flowering has completed, it is not necessary to treat. Fungicides such as an organic copper can be used to help control it in heavily affected plants.
Caterpillars, iris borers, leaf miners, snails and slugs can sometimes be a problem. Most do not cause severe damage, and plants typically bounce back with no issues. In severe infestations, you can use a systemic pesticide but follow the label directions strictly. You also can try organic options. Remember, insecticides not only control the pest problems, but they may also harm pollinators.
Irises can be fertilized in the fall in late October or early November when they begin actively growing again. They can also be fertilized in the springtime just before flowers emerge to give them a boost for flower production. Use slow-release granular or liquid fertilizers. You can also try organic options such as compost or worm castings to help improve the soil.
Cut faded flower blooms off where the stalk emerges from the foliage to prevent seedpod formation and to conserve energy for future flowers.
Louisiana Super Plants is the AgCenter’s educational program that promotes university-tested, industry-approved plants. For more information on the initiative and a list of previously announced Super Plants, visit www.lsuagcenter.com/superplants.
The Boiled Crawfish Louisiana iris is a gorgeous burgundy and yellow selection. Photo by Ashley Edwards/LSU AgCenter
The Creole Can Can Louisiana iris has a deep purple, almost blue, flower. Photo by Ashley Edwards/LSU AgCenter
The Southdowns Louisiana iris is a gorgeous yellow selection. Photo by Ashley Edwards/LSU AgCenter
Divide large clumps of Louisiana irises while they are dormant in late summer. Photo by Heather Kirk-Ballard/LSU AgCenter
Louisiana irises begin blooming in early spring and continue through May. Photo by Heather Kirk-Ballard/LSU AgCenter