"I wonder if the snow loves the trees and fields, that it kisses them so gently? And then covers them up snug, you know, with a white quilt; and perhaps it says, "Go to sleep, darlings, till the summer comes again."-Lewis Carroll.
The historic amount of snowfall this winter looks beautiful in our parks, but poses some challenges to trees and shrubs. Some obvious impacts are snow and ice breakage. Species with brittle wood, such as elms and zelkovas, can lose limbs from the weight of the ice and snow, especially during windy snowstorms. Another common impact is from salt, which is commonly spread on roads as ice melt. Salt gets into the water that is taken up by the trees, and can also be blown onto trees by the wind. Most trees cannot tolerate much salt exposure without suffering significant dieback. Some other impacts of the wintery weather are less obvious. Prolonged very cold temperatures can cause root dieback, although the amount of snow we have had does provide insulation. Most winter damage to plants is not caused just by the cold temperatures, but by fluctuations in temperature. Trees can develop "frost cracks" caused by the winter sun, along the trunk of the tree. And evergreen trees are susceptible to "winter kill", which happens on sunny winter days, when the sunshine tricks the tree into trying to photosynthesize. The problem is that when the ground is frozen, the tree cannot draw water up through its roots, which is required for photosynthesis. This results in dieback of the tree.
Fortunately for us, the ongoing tree care that the Friends provides in our three parks creates resilience to stress in the trees. The pruning that we've undertaken in all our parks reduces the likelihood of snow and ice breakage, and stimulates the trees to grow more vigorously, which enables them to withstand the stress of the cold temperatures. One unknown of this historic winter of deep snowpack - estimated to be the equivalent of 4"-7" of water - is whether our trees will become susceptible to soil and tree-related diseases that are caused by excess water in the ground.
Nevertheless, and although it is hard to believe now, spring really is right around the corner. The trees will shake off their dormancy and many will burst forth their flowers, followed by their new, pale leaves.
Claire Corcoran is an ecologist and member of the Friends of the Public Garden Board of Directors. She is a self proclaimed "tree hugger" and dedicated advocate for greenspace in Boston and beyond. Claire lives in the South End of Boston with her husband and three children. Claire also wrote the recent post, Explaining the Odd Shape of Trees in Winter - Load Reduction Pruning.
