Published: November 09, 2009 03:29 pm      

PLATEAU GARDENING: Getting Christmas cactus to bloom

Plateau Gardening reader Sue of Crossville sent an e-mail asking, “What have I done wrong? I got this Christmas cactus years ago. It is a Zygocactus truncates according to my flower book. The plant was growing in a shallow amount of poor looking soil. I changed the pot and dirt in the spring of 2008. It normally blooms in early June but had no flowers that year. Though it has been getting new shoots, it did not bloom in spring-2009 either.” 

Two pictures from 2007 (the last time the plant flowered) were attached to the message. These photos showed many pink, double blooms at the tips of long, flat, dark green succulent stems hanging down from a pot. The plant is truly beautiful when flowering.

Answer: Success with a houseplant sometimes hinges on providing conditions like the native habitat for that species.Cacti in the botanical family “Cactaceae” are native to North and South America. (Cacti is the plural form of cactus.)

The word “cactus” brings to mind an arid desert environment — sunny, extremely hot by day but really cold at night. That’s misleading, as Christmas and other holiday cacti are not desert plants. Tropical cacti need bright shade rather than direct sunlight, prefer cooler daytime temperatures and must have high humidity. These cacti are tropical plants native to Central American and South American rainforests.

Christmas cactus are sometimes called “orchid cactus” because they are classified as epiphytes, as are many orchids. An epiphyte grows on another plant, using that other plant for support. Epiphytes aren’t parasitic because they produce their own food through photosynthesis. Spanish moss, staghorn ferns,and lichens are also epiphytes.

My research indicates flowering is favorably influenced by a longer nighttime to daytime photoperiod, by cool nights and less soil moisture. Provide these conditions starting about 45 days before you wish to see flower buds. Learn more of what experts advise about growing Christmas cactus at the website www.humeseeds.com/xmascactus.htm or read “Christmas Cactus FAQs” and “Care of Christmas Cactus After Holidays” by B. Rosie Lerner, a Purdue  Consumer Horticulture Specialist at www.hort.purdue.edu/ext/cactusFAQs.htm.

2009 produced a lot of rainfall during August and September. Despite all that moisture, some of my cacti formed buds in September. This may indicate dry soil isn’t as critical as experts say. Orange-flowering Thanksgiving cacti sitting on my deck until the first week in October 2009 not only set buds, they were blooming on Halloween night!

Repotting your Zygo-cactus probably caused the lack of flowers in 2008. Repotting is usually performed when new growth is seen in spring but that maintenance should not be done just ahead of expected blossoms. The late spring bloom you historically experienced with this plant indicates it is a variety naturally programmed to flower in springtime rather than at Thanksgiving or Christmas. Another factor is that these types of cacti seem to bloom most reliably when pot bound.  Once the plant’s roots fill the new pot and if conditions are right for bud formation, it should bloom again. Perhaps that’ll be at the end of 2009 or in spring-2010. Don’t fertilize it. Temperatures of 45-55 degrees produce flower buds. Keep the plant on your unheated screened porch until a frost or freeze is forecast. A freeze can be deadly.

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Plateau Gardening is written by Master Gardeners for those tending home landscapes and gardens in Tennessee’s Upper Cumberland Region. Contact UT Extension Cumberland County, P.O. Box 483, Crossville, TN 38557, (phone 931-484-6743) for quick answers to specific questions, free publications, or to learn about becoming a Master Gardener. Email comments or yard and garden inquiries to Master Gardener Rae, mgardenerrae@frontiernet.net.