Hold off on cutting back plants hurt by cold
If you’re thinking we’ve had a mild winter, you’re right.
Since a bone-chilling, below-normal cold spell at Christmas, we have been much more above normal than below. So far, our winter has basically been 12 days in December and the first four in February. From
Dec. 18 through 29, we saw daily average temperatures of 10 degrees below normal. And Dec. 23 through 29 they were 13.2 degrees off the normal December monthly daily average of
46.1 degrees. Those were seven straight days of hard freeze temperatures (defined by the National Weather Service as at or below 28 degrees). And then Old Man Winter took a month off.
The daily average temperatures for December and January were 2.1 degrees below and 5.6 degrees above the normal, respectively, according to the
National Weather Service in Norfolk. By all measures, that flip-flopped the norm.
But just when you were thinking we were on Easy Street — boom! The Old Man returned the first weekend of February and brought three days of hard freeze. Where things go from here, I don’t know. But if you think this is it for the cold, I’d advise, as they say on the farm, “Don’t count your chickens until they hatch.”
Some of your plants may not have escaped our sketchy winter completely. I’ve seen some signs of winter damage around the area after both cold spells. If your plants have been hit, here’s what you should do: Be patient.
That’s what experts recommend before going all-in now and hacking back plants that appear to have sustained winter damage. It is better to sit tight and wait until spring growth emerges, so you can more accurately determine the extent of any injury. Jump the gun and you can risk removing viable growth. Your heavy, premature pruning can
have unintended consequences for future plant architecture and health.
Temperature isn’t the only factor in the extent of cold injury. Others are plant species, age, health, severity of cold and time of exposure, location, soil moisture and plant culture. Mild fall temperatures that prevent proper hardening off, followed by a sudden drop in temperatures to well below normal, create a perfect scenario for winter injury.
With significant shoot dieback, a plant’s delicate root-to-shoot balance can be upended. That means you should recalibrate your spring cultural practices. Forgo fast-acting nitrogen fertilizers, which may stimulate growth of suckers and water sprouts. Carefully monitor the plant’s water needs; overirrigation may damage a root system that is now out of balance with the plant’s growth.
Because of this goofy winter, the colorful displays from some of our spring blooming trees and shrubs may not occur this year in the way and time frame we are accustomed to. Things may not be pretty now, but with a little luck they are not as bad as they might appear. Keep a close eye on your plants. Fortunately they are pretty resilient.
And one more thing (or two)
Depending on your reference point (meteorological versus astronomical), we are 10 days or about a month from the calendar date of spring. But except for this last speed bump in early February, it seems as if spring has been here for a good while. What do the plants think about all of this?
Let’s look to the science of phenology, which studies the relationships between life cycles, such as those of plants and animals, and environmental conditions. Heat accumulation, as measured in growing degree days, is a good predictor of such phenological transitions, such as bud break in a particular species.
Collaborators for the National Phenology Network have collected, monitored and analyzed data that confirms that these thresholds are coming earlier and earlier each year. Compared to the 30-year average (19912020), as of Feb. 6, spring leaf-out is 11 days earlier than normal in Norfolk. Just call it an early spring.
Visit the National Phenology Network, usanpn.org, and learn more about how you can participate.