Siberian iris are among the hardiest perennials I can think of. There were clumps of white iris, and deep purple iris around the house when we moved here 30 years ago. I’ve moved clumps of these around the garden, I’ve given them away to friends, donated them to plant sales, and I’ve even tossed divisions into the field and over to the edge of the road – see above. I don’t want you to think I planted them by the side of the road, I mean I threw them on top of the weeds. I don’t think any of them have ever died. This is obviously a plant that doesn’t need coddling.
If you want to buy Siberian iris I can think of no better nursery to recommend than Joe Pye Weed’s Garden. They have a fantastic selection of Siberians in many colors. They have not paid me to say that!