When first introduced to the United States in 1825, poinsettias or Euphorbia pulcherrima were named “Painted Leaf” and “Mexican Fire Plant.”
In 1822, Joel Roberts Poinsett, who was ambassador to Mexico at the time, sent cuttings back to his plantation near Georgetown, S.C.
Poinsett began his diplomatic career posting at Veracruz and visited Taxco de Alarcon in southern Mexico, where he discovered the poinsettia.
A friend of Poinsett, John Bartram, took this new plant and raised it in 1828. In June of the following year, Bartram exhibited this new euphorbia at the Philadelphia Flower Show, the first exhibition by the Pennsylvania Horticultural Society.
Since then, we have adopted this plant as the best-known Christmas flower in the United States, and growers have had a chance to modify and improve for color. One of the many ironies of this plant is that this beautiful flower is not a flower.
The color you see on the plant is the leaves. The poinsettia is also the best-selling potted plant each year, as recorded by the magazine Greenhouse Management. Seventy million pots of Poinsettia come into bloom and sell in 6-weeks before Christmas.
Knowing that Poinsettias are from Mexico will help us get these Poinsettias to bloom again.
Wait! The yellow flowers on the very top of the Poinsettia are the only flowers on the plant. If you ask how to get your Poinsettia to bloom, it won’t happen. The part of the plant that turns red in time is not a flower but a leaf.
The leaves on our trees change color in the Fall, as prompted by the change in the length of days here in Ohio. The same basic principle takes effect when we look at the leaves that change color in the Poinsettia, which we call flowers.
Twelve hours of darkness starting Oct. 1 is the start of this process. Keep this date in mind next year to get your Poinsettia to come back into bloom.
Imitating this length of day will fool this photo- periodically sensitive plant into thinking that your plant is back in Mexico and will start preparing to come into bloom.
When I took the greenhouse management class at Ohio State University – Agriculture and Technical Institute, Dr. McMahon taught us about the consequences of photoperiodism in the form of DIF—a simple term but complex in implementation.
On a commercial basis, growers roll out dark cover fabric over the benches where the poinsettias grow. For 12 weeks beginning Oct. 1, the Poinsettias must be kept entirely in darkness for 12 hours daily.
In three weeks, color develops in the leaves. Poinsettia owners trying to do this at home need a spot in a closet to get them to turn colors that block all the light out. Patience is required to understand that this is a three-month process.
The top leaf of the Poinsettia produces a bracht, and the leaves that surround the flowers are typically white. In our light-polluted living of always having lights on, creating 12 hours of darkness each day and causing the bract enzyme to turn red is an issue.
Shade clothes and timers cause the leaves to change color in the Poinsettia.
Even in Mexico, we try to imitate the shortest days around Christmas, which causes the enzyme to change the pigment to red instead of green.
Poinsettia rebloom
To help the Poinsettia rebloom:
1. Cut the plant back to about six inches.
2. Start this pruning three months before you start your light treatment.
3. From the end of July to the beginning of August, prune your Poinsettia.
4. Stop watering the Poinsettia for about two weeks or until the leaves start falling off.
Usually, a small drought occurs in Mexico in the Fall, causing the Poinsettia dormancy.
At this point, we begin the blackout treatment we have talked about. The regimen allows the plant to be in exactly 12 hours of complete darkness.
As this time ends, you must remove the plant from the dark to the light for another 12 hours and repeat until you see the bracts changing.
After a few weeks, you will see the results in moving the plant from dark to light. One needs a blackout room, a blackout curtain, or dark closets you don’t use. Consistency is critical to turn the leaves red.
As with any plant, fertilizing with proper nutrients is critical. The Poinsettia grower must use a balanced, water-soluble fertilizer every two weeks. Follow the basic directions on the fertilizer.
Over-fertilizing can be as much of a problem as under-fertilizing.
Cool drafts will hamper the growth of the Poinsettia. Remember to water your Poinsettia after removing it from its sleeve and putting it where it can drain. Take standard care of your plant.
Practice consistency and caution to produce plenty of pleasing blooms for your Poinsettia to prosper.
The Christmas season has started, and some teens have been on my outdoor thermometer.
One thing that warms me is that tropical plants like the Poinsettia can give me warm thoughts. I hope all of you have had a good season. Try to extend your gardening in some form.
If you have any gardening problems indoors or outdoors, you can email me at ericlarson546@yahoo.com.
My website is www.ohiohealthyfoodcoop.org. You can find links to the blogs to leave comments soon. Thank you for participating in our column.