Make no mistake about it, there is some bitter cold headed our way. Northeast gardens have been tempted with mild temperatures so far this winter and many of us have noticed that sprain bulbs, perennials, shrubs and trees have responded by emerging from the soil or pushing out flower buds. So, what should be done to protect these plants from damage?
Well, there is good news and not so good news. But before we get to the answers let’s assume a few things:
- The plants are native to our area, or at least hardy to it
- The plants are placed and planted correctly
- The plants have not been fertilized recently and were able to acclimate or “harden off”.
OK, so we’ve seen our share of damage in the landscape this past year with tornadoes, hurricanes, pre-season snowstorms, and more. It would be just heart-breaking to see more damage after repairing or replacing that already lost. When it comes to protecting ornamental plants from winter damage we are first concerned with structure and second, transpiration. So, will the stem withstand strong wind, heavy snow, or accumulating ice (remember, we’re assuming they were planted correctly so we’re not including heaving from freezing and thawing)—this is one of the many reasons why proper pruning of ornamentals is so important—and which plants are most prone to loss of water through leaves?
Just reading the second concern you probably already guessed that we really only have to be concerned about evergreen species, as deciduous plants and plants that “die back” to the ground don’t have leaves and therefore stomata, during the winter (although there are other concerns for some species due to the fact that they are not yet fully acclimated to freezing temperatures this season). So, we are left with evergreens and in many cases they have their own defense mechanisms to prevent water loss, but in situations where the ground is frozen and the air temperature is high enough to trick the plant into transpiring, there is a net loss of water. We see the result in broad-leaved evergreens like Rhododendrons when an exposed branch’s leaves are rolled AND brown (there are interesting phenomena that take place which cause the leaves to droop and curl in order to protect itself—the key is the leaf turning brown, as if it were sun-burned). What can be done? In some cases an anti-desiccant can be applied, but it is best not to rely on this remedy. It is always better to site the plants in a place shaded from winter’s noonday sun, more than likely to the north of the house or other tall structure or planting.
We should NOT wrap a plant in plastic, canvas or other impermeable cover to keep it warm—at least here in the Northeast. In rare situations when we inherit a weak or poorly pruned specimen we may drape it in burlap only for the purpose of protecting against broken branches (think: structure), and then as soon as the danger has passed it is removed. Wrappings can cause conditions similar to that inside a greenhouse which would cause the plant to come out of dormancy too early or suffer sun scald. They also provide excellent shelter to critters which feed on the very plants we’re trying to save.
As for the bulbs and perennials we can quickly cover any exposed parts with leaves from yard. We don’t want to use any bark or wood mulches, composts or other material that is actively producing heat. Again, we don’t want to produce a situation where we are forcing plant growth. Just cover them to protect against cold winds and significant others or pets from stepping on and crushing them. Snow is a great cover—if there is any nearby.
So what is going to happen to all of those buds and perennials that have been tempting us with feelings of spring? In all likelihood there will be some damage. In the case of ornamentals it might be a less showy presentation of early spring flowers. If the existing buds survive the harsh cold there might be some visible “winter burn” on them. Some plants might even put out a second, smaller flush of flowers. In the end, spring will come and we will garden again.
Gardens Are