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As I write, I am comforted by the snow that has accumulated on the boughs of my Nordmann fir and Serbian spruce. It is beautiful, yes, but more important the snow serves as an insulator against desiccating winds and frigid temperatures. We must not forget that evergreens, particularly broadleaf evergreens like rhododendrons and American hollies, lose a great deal of moisture through their leaves in the winter.
Winter desiccation is not unusual, but the effects are magnified coming out of a season of drought. Most of us saw little to no rainfall after the second week of August through October. This late season drought will have consequences for plants for several years, so do not be surprised if some things don’t make it through spring bud break.
My husband and I took a walk one day and ambled around our neighbor Stan Humphries’ nursery (that’s what plant people do for fun, I suppose). In the process, we bumped into Stan who made an acute observation…that most of the plants that have already died due to drought stress were in areas that held water and were poorly drained. These plants were acclimated to a wet environment and thus had shallow root systems, which made them more vulnerable to drought stress (in addition to the heat of the summer, likely surface soil temperatures where a bit higher, too). The first casualty at the farm was in precisely that sort of location, and it was an evergreen; so there was the triple whammy of shallow roots, no water and desiccation.
So, here we are now in the middle of a rather chilly cold spell, but the blessing is the snow because it will help to offset winter desiccation. But with snow, deicing agents are soon to follow and this can really do some damage to your plants.
Common deicing agents come in several forms: sodium chloride (rock salt) is probably the hardest on plants; calcium chloride and potassium chloride, if used excessively, can leach into the soil at dangerous levels for plants, but they will not cause the same foliar burn as rock salt. However, calcium and potassium chloride are preferable over rock salt by far.
Basically, try to avoid using products that have sodium in them, which harms plants and avoid ammonium based products if you are worried about your cement. Instead, try fireplace ash or cheap kitty litter; they won’t melt the snow, but they can provide reasonable traction on walkways without causing injury to plants.
We do not have control beyond our own landscapes and while the salt brine used to keep our roads clear is fabulous, understand that it may cause desiccation and injury along our roadways and in parking lots. While the brine is a vast improvement over rock salt, spread everywhere it may still spray or leach into soils once the big thaw begins. Salt spray damage is usually replaced by new foliage come spring, but salt leached into the soil can have more injurious effects.
Salt-contaminated soils can damage plant roots, which means it cannot take up nutrients and moisture; contaminated soils can also make some minerals unavailable for absorption by plants (resulting in yellowing foliage due to chlorosis). The stress of it all can make trees more susceptible to things like cankers, rot and wilt diseases, which would otherwise not affect a healthy tree.
Some plants are more tolerant of salt, including many oak species and ornamental pears. Those that are intolerant include other favorites such as birch, sugar maple and beech. If you suspect salt stress for these species, you may want to flush the salt from the area by watering once the ground thaws.
(Jeneen Wiche is an avid gardener from Shelbyville. She can be reached at www.JWiche@shelbybb.net.)