[Image: Louisiana Iris]The active growing season for Louisiana irises is different from most herbaceous perennials that are typically dormant in winter. Louisiana irises begin to grow as the weather cools down in October and continue to grow until April when they bloom.
After all the flowers on a stalk have bloomed, cut the flower stalk off where it emerges from the foliage. Cutting here prevents seed pod formation. Making seeds is a wasted effort unless you are breeding Louisiana irises. The energy put into making seeds is better put into strong rhizome growth and future flowers. In addition, the heavy seed pods pull the plant over, causing it to flop unattractively.
By June, the irises go dormant, and some or most of the foliage turns yellow and brown. During summer dormancy, feel free to trim off the yellow/brown foliage to make the planting more attractive. Irises usually are at their most dormant (although some green foliage may remain) in August and September. Those that receive abundant moisture and those growing in aquatic situations generally do not go as dormant as those in drier conditions, and more of the foliage stays green through the summer.
The best time to dig, divide and transplant Louisiana irises is in late summer -- August through early October. Dividing clumps of irises is a way to control the size of the clump, invigorate clumps that have become overcrowded and propagate irises to plant in other areas or share with friends.
First, dig up a clump of irises. Locate the new rhizomes that have green foliage at their tips. These will bloom for you next year. Cut those rhizomes from the old rhizomes. Replant the divisions immediately back into the bed or into containers.
If you would like to rework the bed after the irises are removed (recommended), wet down the irises and cover them to keep them from drying out.
Replant the divisions into the reworked bed, spacing them 8 to 10 inches apart with the rhizomes at or just below the soil surface. The irises will grow in the direction they face, so keep this in mind when planting. Finally, water them in and apply a 2 inch layer of mulch.
Mulching is an essential part of good culture for Louisiana irises. The rhizomes of Louisiana irises lie on or very near the soil surface. During summer, the sun can shine directly on the exposed rhizomes once much of the foliage has died back. This causes a condition called sunscald that damages the rhizome and may cause it to deteriorate and rot. The tip of the rhizome will continue to grow, but it is unlikely to bloom the next season. Sunscald is one of the main reasons for failure of Louisiana irises to bloom consistently.
For more information, come by or call our Acadia Parish office at (337) 788-8821.