I have heard the same thing. However, it has never been a problem for me or for my mother. Who by the way moved her iris at a very inappropriate time. If your iris are buried too deep they are probably;y not going to bloom any way so what have you got to lose. I would also recommend fertilizing your iris. When planting bearded iris top dress with a low nitrogen fertilizer and in the spring each year top dress with a low nitrogen fertilizer.

Thanks for any info…it’s quite frustrating as I’ve “rescued” Iris from old homesteads and also bought very expensive rizomes from Iris Farms and still don’t see too many blooms each season…

There are many reasons iris won’t bloom. There are also many types of iris. Since you didn’t mention which type of iris you have, I am going address this question as a bearded iris issue.
The two most common reasons that bearded iris won’t bloom are: buried too deep and not enough light. The iris rhizome should not be covered with soil and should not have much mulch, if any, on top of it. When the rhizome is covered it will produce lush green foliage and no blooms. Bearded iris need a minimum of six hours of direct sun a day to bloom well. Start with these two reasons and see if either one is the reason your iris won’t bloom.

Other factors including improper watering, insufficient phosphorus and too much nitrogen, overcrowding and late freezes can also inhibit blooming. Check your conditions and see if you can determine the cause. Please let me know if you need more information.