Mid-autumn and late-spring snowstorms can lay heavy, wet snow on the branches of woody trees and shrubs, causing them to bend and twist. Sometimes the weight of the snow can cause limbs to crack and possibly sever altogether, but knocking the snow off of branches that are simply bending can be much more damaging.
When a homeowner sees branches bending over from heavy snow load, the first instinct is to grab a stick and start whacking the branches to get the snow to fall off. By whacking branches, the bark and buds can get scratched and damaged, causing a great deal of problems.
Plant material that is holding heavy snow load is already under a great deal of stress. During the mid-autumn and late-spring, the plants are very sensitive, as they are in the middle of a seasonal transition period. During these transition periods the vascular cambium is vitally important, because the plants are hard at work.
The vascular cambium is a thin layer of material between the bark and the wood of woody plant material, whether trees or shrubs. It is the green stuff a person sees if he or she scratches the bark of live plant material. The cambium is the plant version of the human body’s arteries and veins.
Scratching or even gouging the bark disrupts the cambium and cuts off the flow of water and nutrients up the plant from the roots. This damage also cuts off the flow of oxygen and hormones down the plant from the leaves to the roots.
In times of stress, the last thing a plant needs is for its veins and arteries to be functioning at a diminished capacity. However, this is only scratching the surface of problems that can be caused.
Open wounds in plant material are open doors for insects and diseases that may otherwise be kept at bay. Plant material, unlike animals, does have the ability to compartmentalize diseases and insects by creating a quarantine zone that closes off the infected area and prevents the spread of the problem throughout the plant. But, during times of transitional stress, the material is putting far too many resources into the transition, and is not as effective with compartmentalization.
Knocking snow load off of woody plant material can also cause another problem with the vascular cambium.
The wood in the center of a branch or trunk is created when the cambium layers from previous years dies and hardens off, being replaced by a new layer. Since plants are very environmentally adaptive, natural wind and other stresses throughout the year cause the cambium to toughen up, creating stronger bark and wood over time.
By knocking the snow load off woody plants, the process of hardening is reduced, making the plant material weaker and causing reduced sustainability, especially in adverse conditions.
Heavy snow on plants can be equally annoying as a recurring cough or an eyelash that is stuck to the eyeball, but the urge to knock the snow off needs to be subsided.
If it is an extreme case of consecutive, persistent snowstorms, and it is truly an emergency situation, the snow can be gently knocked off with the soft edge of a broom, but much care needs to be taken into this practice.
Even though a broom may not scratch the bark, it can still weaken the cambium and knock off the valuable flower and growth buds. Even during the winter, when the plant is hardened off, the buds are always growing, and these buds are in major developmental periods during the spring and fall. Knocking them off can also reduce the sustainability of the plant material.
Knocking snow off of woody plant material may seem like a good idea, but it is a practice that should be avoided. This action usually does more harm than good, and it is not worth damaging the plant material in an attempt to help it out.