Of course there are "triggers" that awaken dormant bulbs - rain at the end of a dry season, warmth at the end of a cold one. I'm still puzzled as to why some crocus flower in fall when many of them bloom in spring. And what advantage does colchicum gain, flowering in fall and waiting 8 months to produce seed. And then there are bulbs that flower in summer, adding a third season into the equation . . . Judy in New Jersey, where an accidentally dug up hyacinth has a nice fringe of white roots at the basal plate.