1 - Poinsettias and other short day flowering plants may stay outside until temperatures near freezing.

Yard and Garden - October 1, 2011

Q.

OK, the days are now shorter than the nights. Is it time to bring my poinsettia plants indoors so that they will bloom this winter?

- M.J.

Santa Fe

A.

You are correct, we have passed the autumnal equinox and days are now shorter than nights. These are the conditions that induce flowering in poinsettias, Christmas cacti, kalanchoe, and other "short day" plants. However, you do not have to bring your plants inside yet. As long as the night temperatures are well above freezing (probably a few more weeks for you in Santa Fe and more than a month in Southern New Mexico). Houseplants kept outdoors are somewhat protected from many insect problems by natural predators that feed on harmful insects. Once you bring the plants inside, the harmful insects may begin increasing their populations, forcing you to take measures to control these insects. As long as you can leave the plants outside, this problem is delayed. When you bring the plants indoors, begin watching for pests so that you can remove them manually or control them with the control measures appropriate for indoor use. This is a good time to consider the needs of these plants when they are brought indoors. All houseplants will need a location with bright light (not necessarily direct sunlight), protection from drafts and dry, hot air from furnace registers. Adequate water, reduced fertilization, and relatively cool temperatures are beneficial for house plants. Short day plants are those that flower in the winter. These require special considerations. Bright light is important during the day, but they must have nights that are not interrupted by light. They should be kept in a room in which lights will not be turned on during the night. They should not be in a window near bright outdoor lighting (street lights and bright security lights). If room lights are needed or if there is bright outdoor light that illuminates these plants at night, you can move them to a closet each night (for approximately 14 hours), or you can cover them with dark fabric or a black garbage bag. Be sure to remove covering material or return them to the light each morning. These plants also develop flowers more readily if they receive cool night temperatures. Temperatures of 60 degrees or lower will benefit flowering. If they are in an unused room, temperatures to 40 degrees are not harmful, but temperatures between 50 and 60 degrees are better. This will help you reduce energy costs and produce the best flowering. Day temperatures can be up to 80 degrees. As mentioned at the beginning of this article. Always watch for insect infestations. It is much better to catch and manage the infestation while the insects are few than to wait for large numbers of insects to severely stress the plants.

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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