Ask Mr. Smarty Plants

If we may use some material  from previous questions, it will save some time:

Let's talk first about native or non-hybridized iris. There are 26 irises native to North America in our Native Plant Database. Of these, seven were shown to be native to Alabama. These are: Iris brevicaulis (zigzag iris), Iris cristata (dwarf crested iris), Iris fulva (copper iris), Iris hexagona (Dixie iris), Iris verna (dwarf violet iris), Iris virginica (Virginia iris) and Iris virginica var. shrevei (Shreve's iris).

But, perhaps you are growing the Iris germanica, bearded iris. This USDA Plant Profile link refers to the I. germanica as "introduced"; that is, not native to North America. The same map shows the Iris germanica NOT growing in Alabama, but we think that information is a little out of date. This site from Floridata will give you more information on the culture of I. germanica. It apparently began as a natural hybrid between I. pallida and I.variegata. Iris germanica is thought to be native to Southern Europe and the Meditteranean, and other species from Europe and Asia have been brought into the breeding, but it has become established all over the temperate world and can be found on road shoulders and old home sites throughout much of the United States and Europe. There are literally thousands of different irises, many of them with commercial cultivar names.

Now, we begin to see the value of using plants native not only to North America but to the area in which they are being grown, as promoted by the Lady Bird Johnson Wildflower Center. When you are dealing with a hybridized and/or non-native plant, you have no idea what characteristics it has bred into it, nor of the ideal way to grow it. With plants native to the area in which you are gardening, you don't have to make as many adjustments in water, fertilizer or even soil content, because you likely already have good conditions for the native plant to flourish.

We found a National Gardening Association website All About Iris that can probably give you better information than we can.We are assuming you have Iris germanica, or bearded iris. There has been so much hybridization of most of the irises that nativity would be almost impossible to determine. It is a very popular old garden flower and you should enjoy it. They are pretty tough and forgiving as we know from personal experience. One thing we would emphasize is no mulch. That rhizome needs some exposure to air, and will rot if it is completely covered. Organic compost in the ground, as it decomposes, will help keep the rhizome warm, but you don't want it to rot. We always made it a point to cut off a blooming stalk as soon as it had finished all the buds on the stalk, right down to the ground. Any leaves that are actually browned can come off, too but we don't think a little drooping is anything to be concerned about. 

Iris brevicaulis

Iris cristata

Iris fulva

Iris hexagona

Iris verna

Iris virginica