I grow hundreds of species of bulbs in pots, plunged to the rim in coarse sand in cold frames. Some bulbs that I grow (none are the tropical amaryllids discussed by Jim SHields and some others) tolerate being crowded, but others need more room. I think the more a plant tends to produce big, thick perennial roots (such as those on the big amaryllids), the more they need big pots. I agree that regular feeding with soluble fertilizer is necessary (I feed once in fall and 3 times in spring). I use the pots primarily to keep these many species separate and identifiable, and also to limit access by rodents. I use either unglazed terra-cotta (clay) pots or plastic mesh pots. Jane McGary Northwestern Oregon, USA