There are many beautiful flowering plants to complement the fragrant evergreens and twinkling lights that adorn our homes in the coming festive season. But the most popular by far is still the poinsettia, Euphorbia pulcherrima.

Native to Mexico, the poinsettia is indigenous to a region near silver-rich Taxco, and the wild it generally grows 6-12 feet (2-4m) tall. But Mexican flame leaf, its other common name, is a popular outdoor shrub in many tropical parts of the world.

Years ago, I took a Christmas vacation to the Canary Islands where 10-foot tall poinsettias grew around the swimming pool, attracting butterflies to the yellow cyathia (tiny, cup-like flowers typical of the euphorbia clan) in the center of the red leaf bracts. Although these colourful bracts are often called “flowers”, they are modified leaves and their purpose is to attract pollinators to the tiny blossoms.

It’s unlikely the poinsettia would ever have become such an important Christmas symbol were it not for the fact that the first U.S. ambassador to Mexico (1825-1829) happened to be a botanist. And when ambassador Joel Robert Poinsett spied these gorgeous red plants on a December visit to Taxco, nothing would do but to have some shipped back to the greenhouse at his plantation in South Carolina.

And the rest, as they say, is history.

Hints for Growing Poinsettias

Paul Ecke Ranch of Encinitas, California, is the biggest grower and breeder of poinsettias in North America, responsible for most of the 70 million-plus plants sold each year. They offer tips for buying and growing healthy plants (including the fact that poinsettias are not poisonous).

· When selecting your plant, avoid any with too much green around the bract edges and make sure the smaller bracts surrounding the yellow flowers are fully colored and lying horizontal; if not, the plant will quickly lose its color at home.

· Buy plants in pots, not cardboard sleeves, since poinsettias displayed too long in sleeves exhibit “epinasty”, a wilting or drooping of the leaves and bracts.

· When bringing your poinsettia home, protect it carefully since just a few seconds of exposure to freezing temperatures can be fatal.

· A poinsettia needs 6 hours of indirect light, but try to avoid bright sun as the bracts can fade. Keep it out of drafts in a spot where daytime temperatures don’t exceed 21C (70F).

· Water it thoroughly when the soil surface feels dry to the touch, but don’t let it sit in standing water.

Getting Your Poinsettia to Rebloom

Poinsettias are short-day plants, meaning their switch from leaf- and shoot-production to flowering is triggered by the relative length of darkness and light levels as winter arrives. This is a natural phenomenon called “photoperiodism”, and poinsettia growers have learned to manipulate light levels in their greenhouses to fine-tune the timing of poinsettia flowering to the holiday market.

If you want to try getting your plant to re-bloom the following winter, cut it back to 8 inches (45 cm) or so in early April. Keep it in indirect sun, water regularly, and re-prune if necessary to keep it bushy, but not after September 1^st. It can go outdoors into a sheltered spot after night temperatures warm to 13C (55F). Repot it around June 1^st into humus-rich potting soil in a slightly bigger pot and fertilize it every few weeks from spring to fall.

Starting October 1^st, place your plant in complete darkness for 14 continuous hours each night; tuck it in an unused linen closet or cupboard, or cover it with a large box that admits absolutely no stray light in the “dark period”. (One tiny flash of light will interrupt the hormonal signals in the plant and it will fail to initiate flowering.) In the daytime, give it 8 hours of bright light. Continue to water and fertilize, and in 8-10 weeks – with luck – you should have flowering plants.

But given how laborious it is to coax a poinsettia to reflower, most poinsettia fans leave the work to seasoned growers and are happy to spend the money each year for a beautiful plant in prime condition.

A few decades ago, the only poinsettia you were likely to find would feature red or white leaf bracts. Then came a rosy-pink. Today, there are hundreds of cultivars in colors that range from pure white through yellowish-white (‘Lemon Snow’), to peach, to rich salmon-pink (‘Maren’) to frilled edges (the ‘Carousel’ series), doubles (‘Christmas Rose’), marbled bracts and even stripes (‘Strawberries ‘n Cream’). And of course, there are still the velvety reds like ‘Cranberry Punch’ that recall the beautiful Mexican shrub that bewitched Joel Poinsett all those years ago.

Adapted from a column that appeared originally in the Toronto Sun

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