Spruce Tree Pruning Practices

Three Spruce Trees in Anchorage

Let's take a moment and talk about proper pruning practices for spruce trees. Like most conifers, spruce trees require little to no pruning to maintain their beautiful conical shape.  Of course, raising the crown for clearance and assisting in the prevention of spruce bark beetle infestation is acceptable, but that’s a discussion for another day.  Trouble arises when codominant leaders form.

Codominant Leaders/Stems

Spruce Tree with codominant stems

Spruce tree with two codominant stems

Codominant leaders or stems begin as branches.  When these branches show aggressive upright growth and reach about 50% or more of the diameter of the parent stem they begin to compete for dominance as the primary trunk; hence the term “codominant leader.”  This growth typically occurs in the upper crown where the trunk tissue is only about an inch in diameter and becomes damaged through wind, ice, or snow loading.    Codominant leaders are especially concerning because they form very weak unions and ultimately fail creating the risk of property damage and will typically cause permanent scarring to the tree.  This is one of the few times that pruning must be done and should be completed sooner rather than later.  If a codominant stem is caught early, it can be removed without any significant aesthetic damage and the tree can make a full recovery.  Making a one-inch pruning cut to remove a codominant stem as it emerges is much healthier for the tree, than say, a four-inch pruning cut made five years too late.  In older spruce trees, pruning will often leave large gaps in the foliage that aren't very aesthetically pleasing.  An alternative to pruning in these cases could be cabling and bracing in the branch union.  This is a procedure where cables and bolts are used to stabilize and strengthen the union and can preserve the life of the tree but can be expensive and requires regular maintenance and inspection to be effective. 

Spruce tree with heading cut

Storm damaged spruce with a missing top

Topping/Heading Cuts

Next let's talk about heading cuts or "topping" as most folks tend to call it. Topping is not considered an acceptable pruning practice as outlined in the American National Standards Institute A300 Tree Care Standards. This antiquated practice permanently scars trees, exposes trunk tissue to decay causing micro-organisms, and can ultimately lead to the tree's death. On spruce trees and most pines, heading cuts made on trunks and branches less than an inch, can cause response growth, or sprouting.  This can cause codominant stems to form, creating an eventual hazardous condition.  Both decay and codominant stems can lead to tree failure resulting in property damage or injury to people.  Homeowners often express concern about the size of a tree next to their home, leading them to the conclusion that it must be topped to reduce the size and make it safe.  In these situations, think about the relationship between the tree species and the planting site.  Ask the question: Does this tree fit here?  Quite often, the answer is no. In these cases, the tree should be replaced with one more suitable for the location. 

There are several key take-away points here:

1. Conifers with codominant stems should be pruned immediately, and the smaller of the two stems removed. 

2. Topping is a terrible practice and should be avoided at all costs.

3. Most conifers grow into perfect and beautiful tree forms independent of human intervention.

If you have questions or concerns about your trees, give us a call. We love talking about trees!