||The Bay Gardener
By Dr. Frank Gouin
It’s Hard Work to Recycle ’05’s Poinsettia in 2006
But if you insist, here’s how
Think twice before you decide to grow-on this year’s poinsettia to flower next year. It can be done, but it takes both science and art to make poinsettias flower in time for Christmas.
The poinsettia is a short-day plant, meaning that it will not initiate red bracks and flower buds if exposed to more than 12 hours of light. For two and a half months, this 12 hours of total darkness must not be interrupted.
The poinsettia makes other demands, too. The plant must be grown in full sun between 75 and 80 degrees and night temperature above 65 degrees. The roots of poinsettia are also very susceptible to rot, and once the upper leaves have started to color, they are unable to tolerate ammonium-type fertilizer.
If you are still set on forcing this year’s poinsettia for Christmas 2006, here’s what you will need to do:
1. In April, prune your poinsettia plant severely. If the plant is single stemmed, prune the top of the plant to within four inches from the surface of the growing medium. If the plant is branched, prune the side branches to within two to three inches of the main stem.
2. Do not water the plant until new growth appears from the buds on the stems.
3. Fertilize the plant with the recommended concentration of liquid fertilizer; consider using fish emulsion.
4. In June, repot the plant in a large container and place the plant near a south-facing window. Twice each month, rotate the plant 180 degrees to encourage uniform growth. Do not place the plant outdoors. Moving the plant in and out of the house will cause severe defoliation due to changes in light intensity and temperature.
5. During the summer months and into early fall, fertilize the plant twice monthly with fish emulsion fertilizer using the recommended concentration.
6. Starting in mid-September, cover the plant each evening at about 6pm with a large, light-proof cardboard box to be uncovered by around 7am the following morning. The cardboard box is to prevent the plant from being exposed to light during the dark-night cycle. It only takes one exposure to light, for only a few seconds, to stop the flowering cycle and delay coloration of the bracks and flowering.
7. Once the bracks have colored, there is no need to protect the plant from light.
My recommendation is to dump the 2005 poinsettia on the compost pile after you’re tired of caring for it. Purchase a new one in 2006.
Ask Dr. Gouin your questions at firstname.lastname@example.org. All questions will appear in Bay Weekly. Please include your name and address.