Ask Mr. Smarty Plants

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. According to this USDA Plant Profile, it is not native to North America, but is certainly well-distributed, including to Wisconsin, as you can see from the USDA map. Strictly speaking, we ordinarily only deal with plants native to North America, but there are a number of irises that are native to North America, that also have rhizomes, and also grow in the same places. Plus, 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.

There are instructions on how to put the rhizome in the ground in the referenced article, and they do recommend that you plant it as quickly after you get it as possible, so we would suggest you should do so right away. They are pretty tough, and forgiving of beginning gardeners, 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.