Photoperiodism, the amount of light or dark a plant is exposed to, affects the bloom of most plants. Some plants need longer periods of darkness and are known as “short-day” plants. Others require fewer dark hours, “long-day” plants.
Many summer flowers and vegetables are in the long-day category. Chrysanthemums, Christmas cactus and poinsettias fall in the short-day category. These plants require at least 12 hours of darkness every 24 hours in order to bloom. Growers can force blooming by controlling the light and dark periods.
If you have poinsettias from last year, follow these steps to encourage blooms in time for the holidays.
Many summer flowers and vegetables are in the long-day category. Chrysanthemums, Christmas cactus and poinsettias fall in the short-day category. These plants require at least 12 hours of darkness every 24 hours in order to bloom. Growers can force blooming by controlling the light and dark periods.
If you have poinsettias from last year, follow these steps to encourage blooms in time for the holidays.
- For no more than 12 hours each day, keep poinsettias in an area where they will receive the brightest light possible. Temperatures should be kept between 65- and 75-degrees F.
- Provide at least 12 hours of uninterrupted darkness to the plants every 24 hours. If a completely dark room or closet is not available, place a cardboard box over the top of the poinsettias. Be sure to seal the openings of the box with duct tape to prevent light from entering. 60- to 65-degrees F is the ideal nighttime temperature to promote blooming.
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