Q.Water Iris
What kind of soil do I use when re-potting Water Iris? Can I buy the soil at The Home Depot or Lowes Garden department? I re-potted Iris last year using “Potting Soil” but every one of them died. I also put Iris clumps that I divided tucked around some boulders and rocks around the pond and they all lived.

Certified GKH Gardening Expert
It is less about the soil, and more about keeping the pot and soil completely or close to completely wet at all times. This can pose a problem for container plants, so Peroxide will become your best ally in preventing infection to your plants. This article will help: https://www.gardeningknowhow.com/ornamental/bulbs/iris/water-iris-plant-care.htm