-
- Articles
Index : Miscellaneous Gardening Topics
-
-
- 35. Plants Fooled by Recent Warm Weather - Top
- Sweet Acacia, Desert Senna, Flowering Plum and even Bougainvillea coming into full bloom in late January and early February is not a typical occurrence. These and many other plants are well on their way to full spring growth at a time they should still be deeply nestled in Winter dormancy. And though the respite from cold weather was welcome, for plants it could spell real trouble ahead!
Flowers are the most cold sensitive of all plant parts. A light frost is usually sufficient to kill most opened blossoms. For early-flowering ornamental plants like Acacia or Senna, it's of little consequence if the flowers are lost to cold, but that's not the case for fruit producing plants.
Peach, apricot, and apple trees now in full bloom are likely not to produce any fruit again this year. If cold comes in the next few weeks, these flowers and the subsequent small fruits that may form will be frozen. Because deciduous fruit trees bloom all at once, when that blossoming "flush" is killed by frost, there will be no back-up flowers coming along to replace them.
Chances are good that we will have more freezing temperatures before spring finally arrives. Last year, we experienced a hard freeze in Tucson as late as March 6th, and our final frost occurrence came on March 20th. In fact, most years it isn't until mid-March that we here in Tucson can bid farewell to cold weather.
In addition to the stimulating of early flowering, the recent warm weather is stimulating new growth. This is a particularly bad situation for frost-sensitive plants such as bougainvillea, lantana and verbena. New leaves are very tender and are easily frozen. In addition, the stems producing these new leaves are laden with moisture and thus, more easily damaged by the cold. Frost sensitive trees like Jacaranda and Indian Rosewood are likely to be injured in this manner as well.
Hardy plants as well can be injured when new leaves emerge too early. This is true for deciduous trees such as Arizona Ash, Mimosa, Locust, and Sycamore. Although freeze injury will be limited to young leaves and not the stems or branches, it will delay normal spring growth. Hardy trees, however, can tolerate several defoliations before any permanent damage is done.
With the unseasonably warm weather, many types of cool-season vegetables have begun to "bolt." This is a process whereby the plant begins flowering; resulting in inedible heads of broccoli and cauliflower. In the case of leafy vegetables like lettuce and chard, flowering causes the cessation of new leaf development. There is nothing that can be done to stop this warm weather flowering, however, crops can be harvested and salvaged prior to the demise of the plants themselves.
One seasonal event that is normal and expected is the winter leaf drop which occurs on many evergreen trees. Mesquite, Texas Ebony, and Live Oak are experiencing normal yellowing and dropping of leaves. This happens over the entire tree and may take several weeks to occur. It also happens at different times for different trees. For example, the leaves of one Live Oak tree may turn yellow and drop off weeks before an individual of the same species and age growing right next to it. The tree may remain leafless for a week, or several weeks, depending on the individual tree and the weather conditions. Not to fear; trees experiencing seasonal leaf drop will develop their spring growth sprit sooner or later.
Finally, there is really nothing that can be done about plants which are jump-started into premature spring growth due to unseasonably warm weather. If freezing temperatures do damage flowers or new growth, be patient. It may take longer than normal for new growth to reappear. In the case of cold-sensitive plants, don't be too hasty to cut off freeze-damaged stems. Wait till mid-march before pruning plants back. If cold weather occurs earlier, the frozen parts will help protect the rest of the plant.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
- Updated: February 9, 2003
-
-
[e-Mail me
the Articles] - [Search
the Articles]
-
|
