1 - Christmas cacti need long, uninterrupted nights, dry and cool conditions to induce flowering.

Yard and Garden January 5, 2013

Q.

My Christmas cactus did not bloom for Christmas this year. I received it as a gift last year when it was flowering and hoped to have flowers again this Christmas. What happened?

A.

The Christmas cactus is an interesting plant. It is a true cactus that grows as an epiphyte (plant that grows upon another plant) in tropical rainforests of South America. As an epiphyte it grows in an environment that may have rain every day during the rainy season, but it dries quickly. It also must survive a dry season. A cactus is well adapted to these conditions. In its native habitat, although it grows near the equator, it grows at a relatively high elevation that becomes cool at night. The conditions of its native habitat are the conditions needed to induce flowering. It must have a relatively dry period that is cool. These conditions must come when the days are short and the nights are longer than 12 hours.

In your home environment, you need to provide drying. That means you should water less frequently than during the growing season, but do not let the plant dry enough to begin to shrivel. You must provide uninterrupted long nights during this period. If you turn on a light in the room with the cactus during the night you may delay or prevent flowering. The final factor, cool night temperatures, is important. The Christmas cactus will not tolerate freezing temperatures, but needs temperatures near of 40 to 50 degrees to induce them to produce flowers. This became very clear to me when I grew a Christmas cactus in an office window. The custodians came in most nights and turned on lights. The plant did not flower for Christmas, but one branch that touched the window and became very cool at night produced flowers at the end of January.

If you can match the necessary conditions, especially the cool night temperature conditions, you may still see your Christmas cactus producing flowers this winter. If it does not flower this winter, then begin drying, cooling, and provide uninterrupted long nights next year in the autumn after the autumnal equinox.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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