Issue: September 23, 1996

Making Christmas cactus bloom on time

Question: When should I begin treating my Christmas cactus to make it flower in time for the holidays?

Answer: Now. Late September is the time to begin flower induction in Christmas cactus, poinsettia, and other plants which are grown for flowers during the holiday season.

Most of these plants flower after being exposed to a prolonged period of long nights. This treatment may be accomplished by placing the plants in a dark closet from 5:00 p.m. to 6:00 or 7:00 a.m. each morning. Do not leave the plants in the dark from now until the holidays. They need light to continue growing, to form their flower buds, and to remain healthy. Another method is to keep the plant in a room which is not entered during the night. As long as lights are not turned on in the room and the window is not brightly lit by a street light, flowering should develop properly. If you must enter the room or if there is bright street light, you can cover the plant with black cloth or a black plastic garbage bag each night. Just remember to remove the covering in the morning.

Some of these plants also need cooler temperatures during this period. Night temperatures of 55 to 60 degrees Fahrenheit are adequate to speed flower development. Day temperatures are less critical, just keep them from getting too hot. That is, don't keep the plants in a room which will consistently be above 85 to 90 degrees.

Enjoy your home grown holiday flowers.

Houseplant pest control

Question: Now that it is getting cooler I began to bring my houseplants back inside. Many of them have insects on them. I don't want to spray insecticides inside. What can I do?

Answer: It is a good idea to begin inspecting and treating houseplants a month or more before you bring them in from their summer outside. Often insect infestations are minimal in these outside plants because natural predators and parasites keep them in check. Once they come inside and are away from the natural agents which have been controlling them, their populations can explode and your plants can look pretty bad. Inside they can spread through a collection of plants rapidly.

While the plants are outside, you have a greater variety of treatment methods from which to choose. You can use appropriate chemical control measures, both organic and synthetic products. Once the plants are back indoors, your treatment options are more limited. There are pest control products labeled for indoor use, but the variety is less. If you have a severe infestation and cannot find an appropriate indoor use insecticide, you may be able to take the plants outside on a warm day to spray them. If the forecast is for a prolonged warm spell, which is common at this time of year, you can leave the plants outside for several days before returning them to their window location.

Once the weather gets colder, you may not be able to take the plants outside and will be able to use only methods appropriate for use inside. Insecticidal soaps are generally safe for both the plant and people. They may be applied to the plant on the windowsill. If you do not want to risk getting the soap spray on the window or surrounding curtains and furnishings, you can move the plants to the bathtub for treatment. For plants which may be injured by soap sprays spraying with a forceful water spray while in the bath tub may be sufficient to physically remove the insects from the plants.

Constant vigilance is necessary while the plants are indoors so that you may treat problems before they become too severe to be treated and before they spread.

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:, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!