Oh, I thought they were potted ! In that case, I would go ahead and plant them in the ground, and treat them as you would any "new" iris...until the ground freezes, then mulch them with some "pine straw', or any type of mulch that's "loose', and won't pack down, (maybe laying some fence wire, or small tree branches on top the mulch ,to keep it in place). As long as the soil is kept 'cold" they won't "heave'...and when the ground loses it's frost...for good, in early spring, remove the mulch.
