Poinsettias shine with lack of light

For those annoying little twangs of seasonal affective disorder that seem to sneak up on you in the days leading up to the winter solstice there’s nothing better than a Poinsettia or two to brighten up a dark corner of the living room.

horticulture-Poinsettia Sparkling punch
PHOTO: Steven Chadwick

And don’t fret about urban legends warning that the plants are poisonous. The milky white sap common to most members of the Euphorbiaceae family may be a mild irritant for some but the foliage is harmless and it would take a sackful of foul-tasting Poinsettia salad to make you feel the least bit queasy. Even so, it might be a good idea to keep them out of reach, for the sake of the plants if nothing else.

Poinsettias were named after Joel Roberts Poinsett, a 19th-century politician who is not only remembered as the namesake of these popular Christmas icons. From 1825 to 1829 as the first United States Minister to the newly created Republic of Mexico, he managed to annoy and offend his government hosts to such an extent that he was also immortalized by the word ‘poinsettismo’, a slang word coined by Mexicans to mean someone or something that is rude, irritating and obnoxious.

In between stints of political rabble-rousing and the death threats that followed, it’s no wonder Poinsett liked to get out of town once in a while as an amateur botanist and obsessive plant collector. He was known to take frequent plant hunting expeditions. It was during one of these late-season forays in the region of Taxco del Alarcon that he became fascinated with colourful bushes of Euphorbia pulcherrima which had turned a dazzling bright red due to the lowering light levels of the approaching winter. He took cuttings from the plants and shipped them back to South Carolina where they were propagated and shared with other growers. It wasn’t long before Poinsettias became a sought-after novelty, and one of the most popular plants of the Christmas season.

In their native Central American habitat Poinsettias can reach heights of three to four metres and are largely ignored as an anonymous and insignificant weedy shrub for most of the year. To attain their brilliant colour they undergo photoperiodism, in which a plant uses phytochromes, a pigment in its leaves, to detect and measure extended periods of darkness. Similar to other short day (or more correctly ‘long night’) plants such as chrysanthemums, kalanchoe and Christmas cactus, when the critical light period is met – usually six to eight weeks of uninterrupted nights more than 12 hours in duration – hormones are released that cue the plant to produce flower buds.

Love them or leave them, they are big business and one of the most anticipated and lucrative seasonal crops, with about 70 million plants sold in North America during the Christmas season. It’s a highly competitive market, with growers scrambling to create an assortment of new colours, shapes and sizes to add to the more than 100 varieties that already exist.

But if you are looking for a unique colour don’t get fooled by those grotesque lavender blue Poinsettias you occasionally see on store shelves. They were invented by an enterprising grower who decided to generate more sales by simply spray painting the foliage of white Poinsettias blue – an indictable offence in my book.

One place that you won’t see any lavender Poinsettias is Allan Gardens, where the gardeners take their plants seriously and the annual Victorian Christmas show is in full swing, continuing until Jan. 12. The conservatories are bursting with endless streams of red, pink, creamy white, variegated and rosette Poinsettia cultivars that are scattered throughout the tropical beds, framing water features and even stuffed into hanging baskets – all of them supplied from cuttings grown at the city’s High Park greenhouses.

Whether you want to give a little boost to the holiday spirit or just want to sweep away the winter blues in a steamy tropical oasis, it’s definitely worth a family visit to this horticultural gem that’s just a hop, skip and a streetcar ride from the Beach.

Steven Chadwick is a professional gardener and horticulturist, and longtime Beach resident

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