According to Veronica Read's book, there can be as many as 6 units in a healthy hippeastrum bulb. Each unit is made up of 3 leaves plus a 4th leaf which is semi sheathing. The inflorescence develops within the axel of the fourth leaf. She goes on to say, that contrary to popular belief, Hippeastrum hybrids are evergreen and do not require a resting period. Linda Foulis Okotoks, AB Canada