Proper pruning is essential for the health and beauty of landscape trees, and improper pruning can damage or ruin the appearance of a tree for years. Given that trees are usually the most expensive items planted on a property, it just makes sense to protect your investment by learning some basic pruning techniques, or by making sure to hire a properly qualified professional.
Note that trees don’t necessarily need to be pruned much, if at all. The main reasons to prune a tree are as follows:
- to train the plant
- to maintain plant health and/or remove dead, diseased, or damaged limbs
- to reinvigorate a tree, and improve the quality of flowers, fruit, foliage or stems
- to restrict growth and/or reduce size
It also very much depends on the type of tree. Certain species, e.g. Crabapple, Plum, and Hawthorne trees, put out a multitude of vertical, interior shoots each year which need to be cleaned out regularly to maintain good airflow and avoid an overly dense, messy looking tree.
When to Prune
Pruning can technically be done at any time of the year; however, recommended times vary with different plants. For example, with flowering trees, you wouldn’t want to prune off buds that will become that year’s flowers! Pruning time also depends on local climate and weather. For example, it is never advisable to prune during a heat wave, as the tree will already be stressed. In general, the best time to prune most plants is during late winter or early spring while they are dormant – i.e. before growth begins.
It also is advisable to limit the amount of pruning done late in summer as it may encourage a growth spurt on some plants. This growth may not have sufficient time to harden off before cold weather arrives, resulting in cold damage or winter kill. On the other hand, if a plant requires pruning to remove dead, diseased or damaged limbs, it is best not to wait any longer than necessary.
Pruning and tree shape
Recognizing the natural form of your tree is always a good start when pruning. In general, it’s best to work with, rather than against, the natural shape of the tree (topiary pruning is an obvious exception). This will maintain a strong structure, resistant to breaking and other defects.
For example, it wouldn’t be advisable to try to prune a naturally pyramidal tree into a spreading form, or a conical tree into a round one. It’s best to make those decisions at the nursery, when you’re picking out the trees to plant in your yard!
What to use
A variety of tools are appropriate for pruning, depending on the job. The main things is to make sure your tools are sharp, as dull blades will make rough cuts, or leave strips of wood that can get infected.
Another common mistake is to try to use too small a tool to cut a branch. New pruning tools will always state the branch diameters they can handle; trying to exceed this will only damage the tool, possibly the branch, and maybe your hand! It’s not worth it!
A pole pruner or pole saw, usually with an extendable handle, is a must for higher branches, and much safer than trying to climb up on a ladder with a pair of hand shears.
Of course, for larger branches, a chainsaw is the preferred tool – provided you know how to use one safely. If you don’t, serrated tree saws (see picture) are a great alternative for medium-sized branches, and often cut nearly as fast.
Making Pruning Cuts Correctly
To encourage rapid healing, make all cuts clean and smooth. Do not leave stubs since they are usually where die back occurs. A stub occurs when a limb is cut between rather than at, either a growth node or the ‘crotch’ where one branch meets another. Understand that the stub will just die back anyway, looking unsightly and creating potential for rot. Also avoid tearing the bark when removing large branches.
Leaving stubs – a ‘don’t’:
Cutting to a growth node or ‘crotch’ – a pruning ‘do’:
When cutting back to an intersecting branch, choose a branch that forms an angle of no more than 45 degrees with the branch to be removed. Make slanting cuts when removing limbs that grow upward, to prevent water from collecting in the cut.
Who should I hire to prune my trees?
If you’re not confident about taking the task on yourself, it’s best to hire a professional. However, be aware that the majority of tree service companies in town are primarily in the business of cutting down trees, not caring for them! What you’re looking for is an arborist – by definition, “a person whose job is to take care of trees and make sure that they are healthy and safe”. Regardless of what they call themselves, you should make sure the person you hire has the horticultural knowledge and experience caring for trees to do the job right. If they don’t, you might end up with this:
Yikes! This is extreme case, but it shows that it can and does happen in town.
In most cases, it is better not to prune than to do it incorrectly. Improper pruning methods often weaken or deform healthy plants. Messy cuts, damage to the tree’s bark, and cuts made in the wrong spot on the branch can lead to infection, damage, and potentially even the death of the tree.
Tree Topping: another big ‘don’t’
All too often, trees are topped to reduce their size. Topping is the process whereby a tree is cut back to a few large branches, usually including cutting off a portion of the central trunk. It is typically done to a mature tree when a homeowner underestimates its mature size.
After 2 to 3 months, regrowth on a topped tree is vigorous, bushy and upright. But the new growth is weak and spindly and can break off during wind or rain storms.
Topping may also shorten the life of a tree by making it susceptible to attack by insects and disease. In short, topping is not a recommended practice, and a reputable arborist will not perform it.
Options to topping: Thinning, Crown reduction & Pollarding
Fortunately, there are good alternatives to topping. Thinning and crown reduction are better ways to reduce the size or volume of a tree. In contrast to topping, thinning removes unwanted branches by cutting them back to their point of origin. Thinning conforms to the tree’s natural branching habit and results in a more open tree, emphasizing the branches’ internal structure. Thinning also strengthens the tree by forcing diameter growth of the remaining branches.
Crown reduction involves the judicious removal of a tree’s outermost branches, leaving its main structure in place, in order to reduce the height and/or breadth of a mature tree. Weight is removed from the end of branches back to a healthy, growing lateral branch, which will then form a new crown. The process reduces long, heavy, or overextended branches, as well as removing damaged or defective branches. If a tree is growing too low to the ground, some lower branches can also be removed to give the canopy a ‘facelift’.
Pollarding can be considered an extreme form of crown reduction, and is a common method in Europe for keeping deciduous trees smaller than they would naturally grow. It is usually associated with a highly formal landscaping style, as the tree’s foliage will tend to have a round, or ‘lollipop’ shape when it comes out in the spring. This may be accentuated by additional trimming to achieve a certain shape. Pollarding is not suitable for any type of tree, and those best suited for it are trees, like Willow, that put out a profusion of small shoots in the spring.
Other trees that can be pollarded include:
- Beech Fagus spp.
- Catalpa Catalpa spp.
- Hornbeam Carpinus spp.
- Horsechestnut Aesculus hippocastanum
- Linden Tilia spp.
- Redbud Cercis canadensis
Pollarding is normally started once a tree or shrub reaches a certain height and maturity, and will be repeated annually to restrict the plant to that height. Although it looks severe (and is quite unattractive in the wintertime), pollarding is not harmful to a tree when done correctly.
Pollarded Hornbeam, formally trimmed:
A pollarded willow tree, untrimmed:
Contact us today to discuss your pruning needs!