From time to time this year I will add gardening advice that I have tried, some from various publications and others from gardeners like myself. This is one I have used over a period of several years with great success, but I leave them alone for 8 weeks or so.
Coaxing sulky Irises by Gwendolyn Anley. The Iris Yearbook 1942
Some Irises have the name for being "bad doers," but I have yet to find one which does not respond to the following treatment. A bin of peat stands in the open in the shade of the potting shed. Healthy offsets from unhealthy rhizomes, plants for stamina and "bad starters"are planted in the moist peat and left for some weeks. Strong new roots start into growth in a very few days, and in three or four weeks time a splendid root system has developed. The ball of roots with as much as possible of the adhering peat must be lifted and tact and planted carefully. I find that plants so treated never looked back.