Early blooming trees, shrubs provide color for landscape but risk late-season frost damage
It is always exciting to see the first of the year’s flowers bloom and relieve us of our drab and colorless winter. There are several trees and shrubs that get a particularly early start. Early flowering trees and shrubs include redbud (Cercis canadensis), native plum (Prunus americana), crabapple (Malus spp.), magnolia (Magnolia spp.), azalea (Rhododendron spp.) and camellia (Camellia japonica). Two very common trees in Alachua County that open leaf buds early are maples (Acer spp.) and sweetgum (Liquidambar styraciflua).
Although the beautiful flowers are a welcomed sight, these plants are engaging in some rather risky behavior. When warm temperatures are sustained for several days and nights, and adequate levels of moisture are available, these plants will be triggered to flower or open their leaf buds. Warm weather in late January and early February have caused some of these plants to begin breaking dormancy.
In Alachua County, frost-free dates extend from March 13 to Nov. 24. Therefore, we have approximately one more month with the possibility of cold temperatures. Plants that have broken dormancy are likely to suffer flower and/or leaf loss if exposed to a hard freeze. Plants that lose flowers will not likely re-flower as it takes all year to create and set a flower bud. As a result, landscapes will lose their beautiful spring color and the plants themselves may not be able to develop a complete fruit set — and thus will not create seeds. Plants that lose newly developed leaves will respond by pushing out another set of leaves. This can be taxing for the plant as it is forced to use energy stores to create new leaf buds. Also, those leaves lost will no longer be able to photosynthesize and create sugar stores for future use. If the frost is severe, older trees may lose a limb or two but will likely survive; young trees may completely succumb to the cold. Another threat to hardwood trees (especially maples) is a condition called frost crack. When temperatures increase, trees will begin to move water from the soil, through their water-conducting elements and into photosynthesizing leaves. If these trees undergo a hard freeze, the water inside of the trunk (xylem) will expand and cause cracks. Cracks in the trunk are entry points for wood-rotting fungi that can enter the tree and begin to deteriorate the inner wood. Eventually, trees with a heavy load of wood-rotting fungi will lose their structural integrity, die and possibly fall over.
Unfortunately, there is little we can do as homeowners or landscape professionals to prevent these trees and shrubs from getting an early start and risking frost damage. If shrubs are small enough, they can be covered with frost-protection blankets to help minimize flower loss.
For more information on caring for cold-damaged plants, refer to the UF/IFAS Gardening Solutions article “Treating Cold-Damaged Plants” at gardeningsolutions.ifas.ufl.edu/care/weather/treating-cold-damage.html.
— Dr. Kevin Korus is the Agriculture and Natural Resources Extension Agent for UF/IFAS Extension Alachua County. Contact him at kkorus@ufl.edu or 955-2402.
This article originally appeared on The Gainesville Sun: Early blooming trees provide color but risk late-season frost damage
