I dig my fall crocus up, split and replant every two years. I plant them 4-6 inches deep. I notice every second year the bulbs, which have grown to baseball size, are protruding out of the ground. Did I not plant them deep enough two years earlier or are they telling me it's time to dig and split them? Also, when is the best time to split them? I have done it both after the foliage dies back in June and after they bloom in Sept., doesn't seem to make much difference.