I did two plantings of Iris 'Canyon Snow'. The first planting (plants purchased from the Payne Foundation) was near the base of a slope, early in the winter or perhaps late fall, wasn't successful - I think I lost two of three plants. The second planting, midwinter, has been very successful. The second planting (plants purchased from the SB Botanical garden) was a bit up on the same slope, so perhaps the iris weren't so water logged or perhaps they had a tab bit more sun or maybe I didn't disturb the roots as much. Whatever the reason, all three of the second planting have been successful and have flowered their very first year.