Spring cold spell can hurt plants
The recent chilly (cold) weather resulted in quite a few questions about plants and the potential for cold damage. “Should I cover my plants?” was the top question. My answer in most cases this past week was, “not necessary.”
When it comes to spring and cold snaps, there are many variables that come into play. The reason we didn’t see major cold damage to plants this past week (mostly perennials and flowers) was that the temperatures were steady and cold before the drop into the 20s.
Frost and freeze damage in the spring depends greatly on the stage of growth of plants. Plants that have been pushing growth and are nice and tender due to warmer temperatures are extremely susceptible.
Though I am not enjoying it, the weather has been on the cool side for the past week or more, therefore, plants haven’t been developing all that much. They are used to the cooler temperatures.
I remember in 2007, around an April Easter, we had a week of really warm temperatures. Daily highs were in the low 70s. And then the bottom dropped out. Temperatures around the Miami Valley went down below 30 degrees and in some places ended up around 25 degrees.
The damage to perennial foliage
and bulb flowers was significant. Foliage was completely gone in most cases. We ended up cutting all of the foliage back and the plants were fine; they bloomed later in the season, but they recovered.
Flowers are the most tender when it comes to spring freeze and frost. They are the most susceptible. My star magnolias were beautiful this year as the weather was perfect, until last Sunday. The saucer magnolias, for the most part, were damaged by the cold.
Spring freeze and frost are much more damaging to fruit trees. As these buds start to come out of dormancy, they lose their winter hardiness. They are much more susceptible to temperature drops.
In fruit trees, the critical temperature, or killing temperature, is defined as the temperature that buds can withstand for a half hour. Ohio’s peach trees, for example, tend to be damaged often by frost or freeze.
There are things you can do to protect your plant if cold temperatures are predicted. Covering plants to keep the temperature below the cover high enough to prevent damage.
Use blankets, sheets, row covers or even cardboard boxes or newspaper; the protective cover needs to “breathe.” Do not use plastic as any leaves or stems that come in contact with the plastic will freeze. Remove any covering as the sun starts to hit the plants and the ice melts.
Again, there are so many variables that are involved when it comes to temperature lows and plants this time of the year. Species and location of plant, stage of development, temperature prior to the drop, etc. are all factors.
The bottom line is, if you are in doubt, cover it! I don’t cover my plants as I have too many to worry about. I let nature take its course and if I need to cut plants back or clean them up, so be it.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at bennett.27@osu.edu.