I have often wondered how a bulb, or other bulbous plant, knows its depth in the soil, or what the effect of trying to move itself might achieve. Is it trying to get dryer, wetter, cooler, warmer, away from the light or oxygen rich air...? Trying to relate this to pot growing is even more complex as pots heat up quite differently, may have wetter tops or bottoms depending on your watering regime, and with nutrient poor growing mediums and ample nutrient rich water, tending to hydroculture, may produce unnatural root systems. I rarely find adult bulbs moving down much in pots when grown in gritty soil based composts, and bulbs that increase quickly vegetatively, or self seed readily, like some Habranthus, usually push themselves up to the surface or burst the pot, whichever is the easier for them. Brian Whyer, Buckinghamshire, England, zone ~8