There’s a common saying here in northern Nevada about our changeable weather, “Wait five minutes!” This spring started with unseasonably warm temperatures that encouraged plants to come out of dormancy. One friend commented that peonies and roses are blooming too early. Some gardeners had to fight the urge to plant tomatoes!
The lovely warm weather was followed by freezing nights and damage to new growth. University of Illinois Extension Educator, Ken Johnson, calls it “Spring teases and freezes.” Caitlin Reinartz from the Urban Ecology Center calls it “False spring.” No matter what term is used, plants are quite vulnerable to these swings as they emerge from dormancy.
How do plants survive these sometimes-drastic fluctuations, especially in spring? Sometimes they don’t. It depends on the intensity and duration of the freeze, the plant’s stage of growth as well as its age, the hardiness of the plant, the time of year and the amount of water actually in the plant and what water is available from the soil.
Plants may not die as a result of temperature fluctuations, but they may produce less fruit or no fruit in the case of fruit trees. Spring bulbs are more adapted to colder temperatures but be damaged from wet snow or cold rain. Perennial plants may bloom less this year. Shade trees, such as my cottonwoods, may have their leaves scorched with cold or experience dieback of new growth.
A plant’s protective mechanisms include the scales that cover the buds, which are like little jackets protecting the potential leaves or flowers inside. If the bud scales open too early, it is likely that the new growth inside will die or struggle to catch up. I have noticed one cottonwood here at home suffering after two false springs in a row. “…the level of resistance of a plant to a given stress will depend on its ability to activate tolerance mechanisms.” A quick freeze after a warming trend may not allow a plant to activate its tolerance mechanisms in its biochemical, metabolic, or cellular structures. Although plants can acclimate, it takes place over time.
Cold reduces photosynthesis. It also changes how fluids move through cell walls and can cause cellular dysfunction. Low temperatures can reduce a plant’s ability to absorb water, causing dehydration. Nutrients cannot be taken up while a plant is cold stressed.
All we can do to help plants survive is to keep them healthy all year long by supplying adequate water, even in the winter, appropriate nutrients and good maintenance.
— JoAnne Skelly is an Associate Professor and Extension Educator, Emerita, University of Nevada Cooperative Extension. She can be reached at skellyj@unr.edu.
