Working in the garden is the last thing most people are thinking about at this time of year, but some people will use this time to have some tree and shrub issues corrected.
You see, fall and winter are great times to prune. In the dormant season, insect and disease problems are much less likely to infest trees through pruning wounds. This is why Elm trees must be pruned only between October 1st and March 31st in Calgary, by law. Pruning in the winter also tends to increase growth rates in the spring, which can be desirable (especially when trying to get things to grow in a climate like ours). With the leaves down, it is much easier for field arborists to see the structure of the tree or shrub they are dealing with and decide where pruning is needed which can lead to a more esthetically pleasing result. When having work done on large trees or having trees removed, the impact on the surrounding landscape is reduced due to the frozen ground and snow cover over tender perrennials and shrubs which reduces the over all impact on the yard.
Another point to consider is what species of tree or shrub you are dealing with as some species such as Birch and Maple are preferably pruned in the summer months while they are in full leaf. As well some spring flowering shrubs will not bloom if they are sheared in the winter. A good example is Lilac, as the shrub is sheared, flower buds are removed which isn’t a health concern but reduces the value of the plant. These shrubs can still be thinned and dead wooded, but trimming of the top is not recommended. If you are unsure what it is safe to prune in the dormant season you should contact a professional arborist to help you decide. Usually a combination of dormant and summer pruning is ideal to ensure all plants are pruned in the best season.