Jennifer Schultz Nelson
Extension Educator, Horticulture
As a gardener, I have a love/hate relationship with snow. I love the way my garden looks softly draped with snow and sparkling with ice, but as the winter wears on this beauty fades and I long to see something bursting into bloom in the garden. Everyone's landscape is covered in a thick blanket of snow thanks to this week's storm. This is a two-edged sword. Good in some respects, bad in others.
One benefit of deep snow cover is that snow is an excellent insulator. Though snow itself is cold, it prevents bitter cold temperatures from penetrating deep into the soil. The colder the soil gets, the higher the risk of damage to root systems of plants.
Another benefit of snow insulation is protecting plants, especially those considered to have "marginal" winter hardiness, or labeled as "tender perennials". It's a bit counter intuitive, but plants under a layer of snow are actually warmer than those out in the open. They also retain more moisture. Plants exposed to cold winter winds dry out much quicker than those protected under snow. It's still a gamble to expect "tender perennials" to survive central Illinois winters on a regular basis, but a good layer of snow may help.
Snow also minimizes the freeze-thaw cycles that happen throughout the winter months. Winter sun on bare soil will thaw it out a bit, only to freeze again once the sun goes down. This causes soil heaving, which can break and expose delicate roots and plant parts to the drying wind. Repeated freeze-thaw cycles are generally more damaging to plants than being at freezing temperatures for prolonged periods.
Without the protection of snow, it's a good idea to mulch plants after the ground has frozen to protect them over the winter. We usually think the mulch is helping to keep the plants toasty warm for the winter, but actually the opposite is true. Mulch added in the winter is intended to allow the plants and soil to stay cold, which minimizes damage from repeated freeze-thaw cycles.
There are some potential problems generated by snow cover. For one, I am quite positive that the local vole population is having a party in my back yard as I write this. Voles, which are very similar to field mice, typically don't venture out into the open, preferring to stay under cover of vegetation to save them from local predators like hawks.
Snow gives them free reign over the landscape, as they can burrow beneath the snow undetected by predators. As the snow melts later this year, keep an eye out for small trails or tunnels in the surface of your lawn and gardens. Unfortunately, voles feast on overwintering perennials and bulbs, so you may find increased levels of damage this spring.
Rabbits also tend to wreak more havoc than usual when snow is deep. Their snowshoe-like feet allow them to travel on the top of the snow, and they can reach new heights. So this spring when you find rabbit damage four feet up on your shrub or tree, it's not because you have been invaded by Labrador-sized rabbits—your local rabbits just took advantage of the snow drifts to find a meal.
Another problem with deep snow cover is the weight of heavy snow can cause damage to trees and shrubs. Gently shake or use a broom to brush heavy snow from shrubs or tree limbs if it appears to be weighing down the plant. But don't get carried away. Limbs that are bent over and covered in ice should be allowed to naturally thaw and may be later propped or staked to add support. Trying to move an ice-encased branch will likely crack it and cause damage.
Ice storms put an incredible amount of stress on trees. Depending on the size of the tree, a coating of ice can increase the branch weight by thirty times or more! Much of this added weight is highly dependent on available surface area.
Even if you don't consider yourself a "gardener", proper pruning of trees is one way to protect your home or other structures on your property. . Some of this can be a do-it-yourself adventure, but potentially unstable, very large limbs hanging over buildings or involved with power lines should be handled by professionals.
Pruning is best done during the winter when the tree is dormant. There are many philosophies on the art of pruning, and many publications dedicated to the subject, but for preventing storm damage the primary focus is developing a solid limb structure.
One general approach is to remove crossing branches, as they may rub together and damage each other, remove any vertical twigs, also known as "water sprouts" as these tend to be weak, and remove whole branches whenever possible. If removing a whole branch is not possible, remove the branch up to a sturdy secondary branch.
Removing whole branches, whether through regular pruning or storm damage repair, requires some attention to detail. Look at where the branch joins a larger branch or the trunk of the tree. There is a ridge of tissue that looks like a turtleneck—this is the branch collar. The collar produces plant hormones that promote natural healing at the cut site.
Leaving a large "stub" of branch extending beyond the collar will not promote healing, and will be unsightly. Cutting the branch off flush with the trunk or larger branch will remove the collar and its healing hormones. The resulting cut will take much longer to heal, and is more susceptible to insects and disease. When pruning at the branch collar, cut at an angle that will allow water to drain from the cut site, and not allow it to pool in the cut, which could promote disease. Use of "pruning sealer" or other such products is unnecessary and not recommended. The tree's natural healing ability is best.
Despite the potential problems, and new landscape maintenance "to-do's" generated by the snow, there is something to be said for the beauty of the world covered in white that made most of us slow down a bit, at least for a day. Even if you hate everything to do with snow, the harsh winter winds will give way to spring, sooner or later. Perhaps we will appreciate it just a little more this year.