I am experimenting this year with growing daylilies in 3 gal. pots. I have dug some trenches wide enough to set some full sized 3 gal. pots down in. Those are what I consider to be my "permanent place-holders", most of my rows have room for 14 pots per row, somehow I created one row with room for 15 pots per row. Then I have planted daylilies in some trade 3 gal. pots(a little smaller than full size 3 gal. pots). So the trade pots are placed down in the full sized pots. The goal being to keep the inner pots cooler so they do not have to be watered so often. I have done something similar with a couple of other rows only instead of digging trenches I have just placed mulch (mostly oak leaves and grass clippings) around the pots (using that mulch for insulation). So far the plants are doing well, but the weather has not really heated up yet.