Caring for those favorite holiday plants

By Lynette L. Walther | Dec 05, 2013
Photo by: Lynette L. Walther Temperature and light both influence blooming of a Christmas cactus.

Illuminating our homes with color and life and holiday festivity, a Christmas cactus or a poinsettia can be tricky to foster once the season is over. But with a few concessions to their specialized needs, you can often keep those seasonal plants and eventually see them bloom again.

• Poinsettias are native to Mexico, and as might be expected, thrive on warm temperatures and bright sunlight. Not cold hardy, they can easily be damaged by freezing temperatures, even cold drafts. A damaged plant will wilt and drop leaves, as will one that has been watered too much or too little. Place your blooming plant where it can receive the maximum amount of sunshine indoors, keeping it evenly moist but not sitting in water which could lead to rot.

The brilliant red or white petals aren’t actually the blooms of the poinsettia, but rather those inconspicuous little yellow structures at their center. And contrary to one myth, they are not poisonous, though some people are sensitive to the milky sap of this plant.

If you have saved last year's poinsettia and want it to flower again this year, a six-week period of preparation is necessary. Known as "short-day" plants, poinsettias can be brought into bloom if they are given short days and long nights. Flower formation is triggered by long periods of uninterrupted darkness.

Provide your plant with at least 12 hours of each 24 in uninterrupted dark. Night temperature also has an effect and should be below 70 degrees F with 60 to 65 degrees F preferred. To bloom a poinsettia, during the day, place the plants in the sunniest location of the house. This high level of light is needed for the plants to have the energy required for good bract coloration. Day temperatures should range between 65 and 75 degrees F.

Uninterrupted darkness means a room in which the lights are never turned on. Or place the poinsettia in a dark closet or cover it with a cardboard box (tape all the seams with duct tape to cut off any light) each night for the required 12 hours. The process takes anywhere between eight and 11 weeks to flower once the dark treatment has been started. Start the dark treatment in early October. The first six weeks are critical. Every night missed during the first six weeks, adds two days to the bloom time. After the six-week dark treatment, the buds should be set and the dark treatment is no longer needed.

• Christmas Cactus (Schlumbergera bridgesii) and Thanksgiving Cactus (Schlumbergera truncate) can provide weeks of spectacular bloom. These epiphytes are native to the jungles of South America. Epiphytic plants grow on other plants, using them for support but not for nutrients. Christmas cactus normally has smooth stem segments and Thanksgiving Cactus has hook-like appendages on each segment.

Both of these cacti like bright indirect light. Too much sun may cause leaves to turn yellow. Household temperatures are fine. Keep soil constantly moist but not waterlogged. These plants seem to flower best if kept a little pot bound. If you need to repot, try waiting until spring. If a segment or two is accidentally broken off, use it to start new plants by placing the stem end in a small pot filled with potting soil. Keep the pot in a brightly lit location, evenly moist and the segment will soon send out roots.

Flowering is induced by temperature and light treatment. Hold the plants at temperatures of 50 to 55 degrees F, and flowering will occur regardless of day length. But temperatures below 50 degrees F prevent flowering. Nights greater than 12 hours long and temperatures between 59 and 69 degrees also can generate flowers. Twenty-five consecutive long nights is enough for flower initiation. Nights will naturally become greater than 12 hours close to the fall equinox. A plant receiving natural sunlight but no artificial light during night hours, will have this 25-day requirement met about October 20. It takes an additional nine to 10 weeks for flowers to complete development and bloom.

With a little care comes a lot of impact with these festive holiday plants. And now you know how to keep them around to enjoy for more than just one season.

Lynette L. Walther is the recipient of the Garden Writers Association’s Silver Award of Achievement, and she gardens in Camden. Got questions, or comments? Visit her blog, and join in the conversation at: gardeningonthego.wordpress.com or ”friend” her on Facebook to see what’s new in the garden day-by-day.

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