Dear All: I have found that regular 5 gallon pots are usually deep enough for Rhodophialas and other bulbs that like to grow deep. A solution for small quantities of bulbs is to take a one gallon or two gallon pot, fill it two thirds full of potting medium, then take another pot of the same size, cut the bottom out, place it inside the first pot and then fill it with potting medium (you then have two pots stacked one inside the other, giving you double the depth). I have had as many as three two gallon pots stacked in such a manner for things like Tropaeolum. Unpotting the bulbs is very easy, since you just lift the top pot out, and the potting soil falls away, exposing the bulbs. Diana