"In general, the flowering response is triggered by a few weeks of more than twelve hours of darkness," says Justice. So when the days start to get shorter and darker, your holiday cactus takes this as a sign it's time to bloom. "Commercial growers expose plants to sixteen hours of darkness for eight days to facilitate bud formation on Thanksgiving cacti," says Justice.
Caring for your Christmas cactus
Justice offers the following tips for jolly Christmas cacti all year round:
- Keep your Christmas cactus in a bright space, but not in direct sunlight. Near an east- or south-facing window in your home is perfect.
- Cool conditions are best, especially in homes with low humidity.
- Plant Christmas cacti in small containers; the roots demand lots of oxygen.
- Re-pot every few years for fertilization. Otherwise, they are slow growing and don't require fertilizer.
- Do not over-water. Remember, these are cacti! If root rot sets in, plants decline rapidly.
- Similarly, do not let your Christmas cactus dry out on a regular basis. They don't like to be parched, either.
Unfortunately, what may have worked to set buds in motion in the past is not always feasible now: "In the past, in mild areas like Vancouver or Victoria, people typically summered holiday cacti outdoors under trees, bringing them indoors at the end of September," says Justice. "Nowadays, however, there is usually too much nighttime light exposure in urban areas and bud set is not reliable using this method."
Christmas cactus cousins
There are two similar cacti to the Christmas cactus that bloom in the spring. The Hatiora rosea has small, short-tubed, open pink flowers and the Hatiora gaertneri has larger, crimson flowers. These are known as Easter cacti and are generally cared for the same way—they just show their colours for different holidays.