Zone 5 How deep to plant

Well I am confused on how deep to plant. I have just redug and planted my iris, I mounded them up on a little hill with the tuber showing. I planned to cover them in Oct with soil. Now I have received a catalog from Cooleys that states they should be planted with light soil covering. If they are too high does this cause leaf flop?
All advise is welcome...
Thanks, Jill

Hi Rosa, I am not very far from you. I plant mine in flat ground in the sun with the top of the rizome just barely above the soil line. You do not want to cover them with anything because it will hold moisture and they will rot. I plant mine in rows with two faceing one way and one faceing the other in between the fist two but not right against them. Then go about 8 inches and plant three more. That way when the walk! or multiply they will go on down the row and fill in. Hope this helps. BEV