It depends on where you are, of course, but if the heat hasn’t arrived yet, it probably will soon. It may come as a shock to the Louisiana irises, but they are tough plants. They will handle the heat with a little post bloom fertilizer and consistent water. If you grow them in standing water or mucky soils, all the better, but in regular flower beds you’ll need to be diligent about watering to keep them green. Once they get too dry, they begin drifting toward dormancy. They may not go fully dormant, but they likely won’t look crisp and green again until the new growth cycle begins in the fall.

If the irises do go dormant, no problem—they will crank up again in the fall. And if the foliage becomes unsightly, cut it back to a few inches above the ground. But if the leaves stay green, let them continue growing. Continued growth means larger rhizomes and, presumably, better bloom. 

Bloom Stalks Be Gone

After bloom, it is good practice to remove the bloom stalks unless you want to collect seed. The sooner you do this after bloom has ended, the better. The irises gain nothing from supporting old stalks, and directing their energy into new offsets is far more beneficial.

You’ll also want to remove the stalks before seed pods mature and begin dropping seeds into your beds. At the latest, this should be done about two months after bloom has finished. If you see seed pods turning yellow or brown in preparation for splitting open, it’s time to act. But why wait? Once bloom is finished, old stalks quickly become unattractive. Your clumps and beds will look much better without them. Do not compost the stalks or any iris foliage—rust spores, if present, can be reintroduced into your plantings. A black trash bag is the safest route.

After the bloom stalks are gone, there isn’t much to do for a few months beyond routine maintenance. Water the plants and remove any yellowing foliage. It’s normal for some leaves to yellow throughout the year, and everyone will be happier if they are removed.

Off‑Season Transplanting

Gardeners often need to replant a Louisiana iris in the “off” season. The hot months are the problem, and we often have no control over when we receive a bare‑root rhizome from a sale or a friend. This is not a problem if a few precautions are taken.

In or near hot weather, a rhizome is best planted in a pot and placed in a shady spot. At minimum, hold it until new growth has begun (and perhaps until fall) before moving it into the garden. The uprooted iris will need ample—but not excessive—moisture in the meantime.

One good practice is to set the pot in a shallow tray of water—an inch or two—so the plant can draw up what it needs. The iris will not want soggy conditions, however. It may seem counterintuitive for a wetland plant, but Louisiana irises grow happily in water only when their roots are established. If you plant a bare‑root rhizome directly into water, there is a good chance it will rot. It needs roots anchored in a growing medium and its leaves above water to survive and thrive.