I never paid any attention, sorry. I just know that, when they are mature plants and things are right for them, they generally bloom once a year, set a spike in the late fall and open flowers in the early spring. Generally it takes a 10 - 15 degree drop in temperature for a while (few weeks?) to initiate bloom. I've been fortunate in growing and blooming them, but have to say I just take care of them and let them decide when to bloom. I know I've less blooms since my MIL came to live with us, she's 89 yrs old and we keep the house warm for her in the winter, so I suspect that affects my flowers. I'm just glad she's able to live with us though and not in a nursing home, she enjoys the pets and the flowers so much.