Extension Communications Extension 4-H Youth Building Ames, Iowa 50011-3630 (515) 294-9915

12/15/03

Contacts:
Aaron Brand, Plant Pathology and Horticulture, abrand@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

Yard and Garden Column for the Week Beginning Dec. 19, 2003

Coaxing Christmas Cacti to Bloom

By Aaron Brand
Plant Pathology &
Horticulture Student
Iowa State University

Growing up, there were three things that were almost guaranteed when I visited my grandmother's house during the Christmas holiday season; a fully-decorated Christmas tree, wonderful baked goods and gorgeous holiday cacti in full bloom.

I also knew others who had holiday cacti that never bloomed. Frustrated indoor gardeners couldn't figure out why the holiday cacti didn't bloom "on cue." Everything imaginable was tried to get the plants to bloom. Using different fertilizers, repotting, using distilled water instead of well or city water, using different watering regimes, and other "tricks" were tried with no luck. Often, the plants were eventually discarded or given away. Other, more persistent indoor gardeners, repeatedly gave their plants "just one more chance" to perform to their expected potential.

As with all plants, it is important to understand what the plant needs to perform up to its potential to create enjoyment. Most holiday cacti fail to flower, not because of improper soil, watering, or fertilization, but because of improper temperatures and, more importantly, lighting.

Following are some hints on how to grow a healthy, happy holiday cactus and get it to bloom for the holiday season.

Soils
Most commercial potting mixes are suitable for holiday cacti as long as they have adequate drainage. Ideally, the mix should have at least 50 percent sand or perlite or some other coarse material. Also, do not let the pot sit in a saucer of water for long periods of time.

Water
Watering should be regular, allowing for the soil to dry between waterings for most of the year. The cactus should be allowed to have a period of time during February and March when water is given infrequently. Holiday cacti are not typical cacti, so they cannot be allowed to become "bone" dry like other cacti. Most cacti that one would think of grow in the hot, dry deserts of the world, but holiday cacti, instead, originate from the jungles of South America and are called epiphytic cacti. Epiphytic means that in nature, the plant grows on the surface of other plants, but is not parasitic (taking food from the other plants). In the case of holiday cacti, they grow in the axils of trees.

Fertilizer
Fertilization should be done using half-strength liquid fertilizer during the periods of normal watering. Fertilizer should be withheld from September through mid November and during February and March.

Temperature
Holiday cacti should be kept in controlled temperatures throughout the year to ensure satisfactory blooming. During the spring and summer months, holiday cacti should be kept between 55 and 75 degrees F. Temperatures greater than 77 degrees will cause growth and development of holiday cacti to be stunted or stopped altogether, although this is not a severe concern in the summer months. The plants will be fine with higher temperatures during the summer months. But from September through November, and again in February through March, nighttime temperatures should be between 55 to 65 degrees to aid in the uniform development of flower buds. Temperatures greater than 75 degrees during these months can cause the death of developing buds. After 4 to 6 weeks of decreased temperatures in September and October, the temperature can be increased to 65 degrees.

Light
Lighting is one of the most important factors controlling the blooming of holiday cacti. These plants are described as short-day, or more properly, long-night plants because they require more hours of darkness than light in order to bloom. In the case of holiday cacti, the amount of darkness needed is 15 to 16 hours per day, and the other 8 to 9 hours of the day should be spent in a bright sunny window. Artificial lighting can be substituted for direct sunlight. The darkness must not be interrupted. If the period of darkness is interrupted by turning on lights, even for a short amount of time, the initiation of buds may need to be restarted, as the plant will recognize a short burst of light the same way it will an entire day. By placing the plant in light conditions with the proper number of hours of darkness for 4 to 6 weeks, the flower buds will be initiated by the plant.

The use of several varieties of holiday cacti in different colors and proper techniques for growing these plants can ensure a spectacular show throughout the winter holidays. If you have a holiday cactus that doesn't bloom well, maybe the right thing to do is to give it just one more chance so that you can enjoy it at its full potential.

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Editors: No photo is available for this week's column.

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