This winter’s exceptional weather was deceiving some popular springtime ornamental shrubs and fruit trees into flowering prematurely. The weather took a turn for the worse last week and the deception is over.
Azaleas, for example, began blooming because there were warm days which followed a few days of cold.
With the return of below seasonal average temperatures to panhandle Florida, many are questioning how this will affect their shrubs, plants and fruit trees in the spring of 2025. A few factors offer the potential answer.
There are a number of variables which determine when a plant will bloom each year, including the sun, water, and air temperature. To understand why the plants bloom, there should be an understanding of “photoperiodism,” meaning the effects of light and darkness on some plant species.
Some local azaleas were prematurely blooming brightly, until a few days ago. The premature blooms gave way to harsh temperatures which removed them and has the potential to diminished the upcoming spring’s bloom.
Certain plants respond to the day length. Some are long day plants which flower in spring and summer, and some are short day plants flowering in fall and winter. Then there are plants which will bloom in any season, identified as day neutral plants.
Long and short-day plants will not be directly affected by prevailing weather conditions. For example, chrysanthemums, which are short day plants, naturally bloom in winter.
These plants can be forced to bloom in summer by keeping them in a dark room for 12 hours a day for several weeks. Many nurseries and florists use this technique and utilize greenhouses with blackout systems. They also use grow lights to produce early season blooms on spring/summer flowers sold for Valentine’s Day in a few weeks.
For those neutral day plants there is “vernalization.” These plants must be exposed to cold weather to some greater or lesser extent.
Most temperate fruit trees need exposure to cold temperatures. When winters are too mild or contain intermittent warmer periods, dormancy is prematurely terminated and bud break starts.
Most of the exposed buds of these fruit trees can survive freezing temperatures, but many of their flowers will be killed if exposed to a late arriving hard freeze or frost.
After the freeze most of the flowers may appear normal, but the center part of the flower, where the reproductive organs reside, has died, resulting in no fruit formation. Covering plants in-bloom provides some freeze protection.
When there is a warm early winter there will be an irregular and premature flowering. Yields in blueberries, peaches, and pears will probably be diminished, if not completely eliminated.
Another consideration is fruit trees or shrubs pruned too early in winter. Warm weather combined with the pruning stimulates the growth of new shoots.
There is a hormone produced in lateral or terminal shoot buds which travels down the shoots, inhibiting their growth. When the terminal shoots are pruned too early, the growth-inhibiting hormone is removed.
The warm days during winter can cause these newly pruned plants to form new shoots. The new growth is tender and very susceptible to freeze injuries. Pruning in late January or February will likely deliver the best results.
For shrubs like azaleas and gardenias, flower buds are set in summer, long before they can be identified by most people. Losing the buds after midsummer, no matter the cause, drastically decreases the number of flowers the following spring.
While it may be too early to forecast spring 2025’s fruit tree yield and azalea bloom performance, it may have been reduced by the late January blizzard of 2025.
Leave a Reply