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Poinsettias can last, if you put in the effort

| Friday, Dec. 28, 2012, 8:58 p.m.
Poinsettias can be coaxed to turn red again next year, but it takes some work. Jessica Walliser

Now that Christmas is over and the new year is about to begin, I typically get many inquiries from folks who are interested in keeping their poinsettias going strong. Many gardeners grow this interesting and beautiful flower as a houseplant through the winter and then use it as a unique outdoor-garden specimen come summer.

A native of Mexico and parts of Central America, this member of the spurge family can reach up to 20 feet tall. On a trip to Guatemala many years ago, I saw a backyard specimen as tall as the dogwood in my own backyard. It was smothered in brilliant, red bracts — the colored, modified leaves we think of as flower petals. It was breathtaking.

Though it would be difficult to grow such a large specimen here in Pennsylvania (the closest I've seen is the 6-foot-tall poinsettia tree at Janoski's Farm and Greenhouse in Clinton), getting a poinsettia to color-up and rebloom again the following Christmas is a big challenge many gardeners enjoy taking on, myself included.

To best care for your poinsettia after the holidays, keep the plant in a bright window but out of direct sunlight. Reduce the watering to once every 10 to 14 days and stop all fertilization. Many of the leaves and bracts may drop off. Shocking as it is, this is not unusual. From this point until April, the plant will be resting; perhaps entering a completely dormant state if all of the leaves drop off. To check if the plant is still alive, bend one of the bare stalks; if it remains flexible, the plant is still alive.

Then, in late April, begin to put the plant outdoors in a shady site only for a few hours during the day if temperatures remain in the 50s or 60s. Bring it back indoors at night and do not expose the plant to frosts or temperatures lower than 50 degrees. Eventually, your poinsettia will become acclimated to outdoor growing conditions and will begin to produce new leaves.

In May, once the danger of frost has passed, repot the plant into a slightly larger container using new potting soil; or plant it directly into the ground. Position it in full to partial shade — no direct sun during the midday. Continue to water it throughout the summer months when necessary and fertilize every two weeks with an organic water-soluble fertilizer-like fish emulsion, liquid kelp or compost tea. In late June, if you wish, you can prune back the plant to promote bushy, compact growth.

Once early September arrives, move the plant back indoors. It is important to do this before the nighttime temperatures drop below 50. Once October arrives, the goal is to mimic the day and night cycles of the plant's native habitat. For without the proper day and night lengths, the plant will not rebloom. This is where the dedication and challenge comes in.

Starting Oct. 1, keep the plant in complete darkness for exactly 14 hours each day. This period of darkness cannot be interrupted by any amount of light. Not a flashlight, no street lights, no car headlights, no closet light, nothing. You may want to put the plant into a closet, close the door, block the bottom with a rolled towel and set a timer to remind you to remove it and put it back into a sunny window after the 14 hours have passed.

That means every day at 5 p.m. it goes into the closet, and every morning at 7 a.m. it comes out, religiously and without fail. Otherwise, it will likely not produce color, though some varieties are more forgiving than others.

Another unique way to provide the hours of complete darkness is to place the plant in a dark closet or basement bathroom with no windows and position a grow light over it. Set the grow light on a timer cycling at 10 hours light and 14 hours darkness per day. Once the plant begins to show color, about eight weeks later, you can discontinue the process and enjoy your beautiful blooms.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Grow Organic” and “Good Bug, Bad Bug.” Her website is

Send your gardening or landscaping questions to or The Good Earth, 503 Martindale St., Third Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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