This is the time to begin conditioning poinsettias, Christmas kalanchoe and Christmas cactus to get them ready for the upcoming holiday season.
They are all short-day plants needing long hours in total darkness. They eventually bloom at their own pace, but if you want them in flower for the holidays prepare them for at least six weeks beginning in mid- to late-September.
These are the basic instructions to stimulate flowering: Place the potted plant in a closet or unlighted room, or cover the plant with black cloth over a frame or a cardboard box for 14 hours. The plant must then be returned to the light each day for at least eight to ten hours. The more you know about each plants’ natural habitat, the more successful you’ll be in helping the plant thrive in your household conditions.
Poinsettias are the most popular flowering plant sold in the United States. Red is still the favorite color, but you can find poinsettias in white, pink, peach, yellow as well as marbled and speckled. They are native to Mexico where the plant is a perennial and grows 10 to 15 feet. The flowers are modified leaves called bracts; the ‘true’ flowers are the small clusters of yellow blooms in the center of the bract.
Poinsettias should be given an application of a high-phosphorous fertilizer this month and again next month to help encourage the development of flower buds. Feed your Poinsettia every two weeks with a high nitrogen fertilizer once color has begun to show.
Kalanchoe is a colorful, long-lived plant that should be treated as a succulent. It has thick fleshy leaves and bright flowers. Kalanchoes normally bloom in January, but they can be forced into bloom at any time of the year by controlling their exposure to darkness. Kalanchoes are now available in many colors: red, pink, yellow and orange.
Be careful not to overwater or overfeed your kalanchoe. They bloom for a long period, 10-12 weeks. As each flower cluster fades remove it and its stem. Once the plant is done blooming, you still have an attractive green foliage plant that will continue to grow. If the plant becomes too large, either repot or cut back the plant to its original size or smaller, and watch it grow again.
Christmas cactus have become a favorite of mine because they perform well year-round. When in bloom the colorful tubular flowers at the tip of each branch are a cheerful sight on dark winter days. It’s easy to start a new plant. Simply break off a branch and place it in a vermiculite medium. They like tight spaces and thrive in pot-bound conditions. So, transplant carefully. In summer, they can be placed outdoors in a shady spot. To encourage blooms, it needs the same general care as poinsettias and kalanchoe with the exception that they must have cooler evening temperatures of about 50 to 60 degrees Fahrenheit. To grow them successfully, it’s important to remember they are not sun-loving, drought-tolerant desert cacti. In their native habitat, the rainforest in the Organ Mountains of Brazil, they receive as much as 17 inches of rain each month from December to March.
When you have questions, Colorado State University Extension has research-based answers. Get answers to your horticulture questions by visiting ask.extension.org any time day or night. You can also visit or call the help desk 719-520-7684 Monday to Thursday from 9 a.m. – 12 p.m., or email CSUmg2@elpasoco.com. The help desk will be staffed with volunteers during those hours through the end of September.