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You Can Grow It: Making poinsettias bloom

Getting these brilliant flowers to bloom in time for the holidays can be quite the process.

Thanksgiving is over and Christmas is just weeks away. And along with all of our other holiday decorations, we’re seeing a lot more of one of our favorite Christmas symbols – those beautiful poinsettias.

When you see a beautiful bright red poinsettia, you know it’s the Christmas season. They’ve been part of Christmas celebrations for centuries. Poinsettias do grow naturally in tropical climates, but getting these brilliant flowers to bloom for us in time for the holidays is quite a process, almost like magic.

Most local greenhouses begin with pre-started plant cuttings in the summer and transplant them into small containers. At Edwards Greenhouses, they grow nearly 10,000 poinsettia plants, with nearly three dozen different varieties, including 10 to 15 different shades of red. The plants all start out green, but then something stimulates their magical color transformation.

“It would be the shortening of the day.”

The color change is triggered by the length of daylight, just like the leaves on trees and shrubs growing outdoors. The plants need several hours of continuous darkness to initiate that color change.

“Fourteen hours is what they recommend,” said Garnette Edwards with Edwards Greenhouses.

“What we do is, usually by September 1st, we have no artificial light on the greenhouse, in the greenhouse, from about September 1st until about the 30th of October.”

And as the days grow shorter, the colors become more pronounced.

What we think of as flowers, the part that changes color, are actually the leaves of the poinsettia, which are known as bracts.

“And those are actually transition leaves on the plant. And they are meant to draw, attract insects that will pollinate the flowers. The flower is actually the little center here, and that is called the cyathium.“

“So the red background and the bright yellow will bring insects from a long ways away to pollinate this.”

Think of it as the plants’ colorful make-up to attract bees and butterflies.

“Well, yeah, this is the lipstick and these are the lips.”

For weeks, the plants stay green. but then, around the third week of October, a subtle change begins, with a hint of red showing up in the leaves.

By mid-November, the full change is underway, as the poinsettias have magically transformed into a sea of vivid shades of red, yellow and white, with the colors growing more brilliant each day.

The classic red shades are by far the most common for holiday decorating, including the Capitol poinsettia tree, in the center of the Idaho State Capitol rotunda.

I managed to keep these poinsettia plants from last Christmas alive through the summer and fall, and I decided to give reblooming a try.

Starting in mid-October, I kept the plants in bright sunlight during the day, and then put them in a dark closet away from any light between sunset and sunrise. Weeks went by without any noticeable change. And then, around mid-November, I started to see some red appearing on the leaves.

I’m hoping that by Christmas, these reblooming poinsettias will look a lot more like these new ones.

The colorful transformation of the poinsettias is truly magical, making it an iconic symbol of a magical time of year.

Here are some tips to keep your poinsettias looking their best through the holidays. Put them in a somewhat cool location with bright, but indirect sunlight, away from any heater vents and drafts. Keep the soil moist but not too wet.

In the spring, once nighttime temperatures stay above 50 degrees, you can move your poinsettia outside for the summer, and then try reblooming it again next year.

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