It can be traumatic when an early hard frost takes out a beloved plant, as in the case of an immigrant "Flame" azalea that came to us through the generosity of a southern relative. In this case, it simply was beyond our control.
We all have plants that we become attached to in one way or another. Perhaps a close friend or relative brought you a plant while you were in the hospital or perhaps you received a lovely azalea or hydrangea for your spring holiday table. In many cases, it's not the plant that matters, but how the plant came to us in the first place and from whom.
In the case of the "Flame" azalea, its demise came without warning. It grew well for 15 years in our garden until one spring two years ago when several warm days were followed by a hard frost. This plant was used to cold temperatures; although it grew wild in North Carolina, it came from the mountains, where snow and freezing temperatures are common. Many flowering shrubs and trees lost their buds that year, and I didn't expect to get any of the brilliant orange flowers we enjoyed seeing each May.
What I also didn't expect, however, was to lose the entire plant by the following year. It just couldn't recover from the devastating blow of that hard frost. But it wasn't even the frost that got it. The plant had survived much colder temperatures over many other winters. It was the tease of those warm days that encouraged bud break and new growth. When the frost hit, the new growth created the perfect opening for intra-cellular ice damage.
When a winter hardy plant prepares itself for cold temperatures, those temperatures are gradual over a long period of time. We notice several cool nights before the first frost eventually hits. By that time, the plant has had a chance to acclimate. This is why we always recommend with new plants from a greenhouse or houseplants that will go outdoors in spring, they are set out for longer intervals each day for about a week or two. Gardeners call this, "hardening off."
But when a winter hardy plant breaks dormancy after several days of high temperatures and sunshine, if a late frost hits, particularly a hard, killing frost, ice crystals form inside the plant's cells. If the ice formation is extensive or remains over a long period of time, the cells will rupture and die.
When that happens, all we can do is wait and see. We might lose most of the blossoms on our flowering shrubs that year. The plant may look weak and spindly all season, but by the second season could recover. Or, in the case of my "Flame" azalea, it might not recover at all.
According to The Ohio State University Extension Horticulture and Crop Science Division, there are several things we can do to help prevent winter damage to our favorite plants, particularly if they are newly planted that year or have a reputation for being sensitive to winter cold and winds.
n Apply a layer of mulch at least two inches deep after the soil freezes. This will keep the soil cold and will help reduce injury from plant roots coming out of the soil due to periods of alternate thawing and freezing.
n Multiple-branched evergreens and shrubs can be damaged by the weight of snow or ice, so to prevent branch breakage, fasten heavy twine at the base of the plant and wind it spirally around and upward to the top and back down again. In some cases, particularly tall, narrow-growing juniper and arborvitae trees, if the branches are pushed down, they are not likely to snap back up in spring.
n Apply an anti-desiccant product to prevent narrow and broadleaf evergreens from losing moisture through their leaves in winter. In many cases, the plant's roots can't take in what is lost through the leaves, and foliage will turn brown and drop.
n Wrapping your plants in burlap will protect it from the drying effects of winter sunlight, wind, and if the plant is close to the street, the harmful effects of de-icing materials on the roadways. Wrap the lower body of evergreens, but keep the top open as even in winter evergreens need sunlight.
n If your plant is likely to become winter food for rabbits, mice or moles over the winter, place plastic collars around the trunks of shrubs and trees or put aluminum foil or hardware cloth around many stemmed plants.
Evanoff is a Master Gardener with The Ohio State University Extension of Trumbull County. She can be reached at firstname.lastname@example.org.