Codominant Tops in Conifers: What Homeowners in the Snoqualmie Valley Should Know
- Jen Wentworth
- 2 days ago
- 3 min read
If you've got tall evergreens like Douglas fir, cedar, or spruce on your property, there's one thing worth taking a closer look at, especially if you're in places like Snoqualmie, North Bend, or anywhere along the Eastside: codominant tops.
They might look like a natural part of the tree's shape, but they can create significant problems, especially with our wet winters and strong windstorms. Below, we'll give you insights on how to protect your trees for longevity and health.
What Are Codominant Tops?
Codominant tops happen when a tree grows two or more main stems (or leaders) of the same size and height, rather than forming one strong central trunk. You'll often see this in conifers like Douglas firs, which are naturally meant to grow with just one trunk for strength and stability.
When multiple tops compete for dominance, the tree's structure gets weaker over time, which can become a real issue in a place like Western Washington, where the weather hits hard.
The Hidden Problem: Included Bark
One of the biggest red flags with codominant tops is included bark. This is when bark gets trapped between the stems instead of fusing as solid wood. As the leaders grow, pressure builds, and the union between the two becomes weak, like a crack in the foundation of a house.
The result? A tree that's more likely to split apart, especially during windstorms or heavy snow. This happens all over the greater King County area, sometimes with no warning.
Why This Matters in the Pacific Northwest
In our climate, codominant tops can make trees more prone to:
Splitting In Storms
Weak unions can give out in heavy wind or snow.
Broken Limbs or Falling Leaders These can damage property or put people at risk. Tree Decline Constant stress from poor structure can leave trees vulnerable to disease or decay.
If a tree is near your house, a driveway, or anywhere people spend time, it's worth checking on.
What to Watch For
Not sure if your tree is at risk? Here are a few things to look for:
Two main trunks that have grown from the same trunk.
A narrow "V" shape where the trunks meet.
Bark is tucked in between the stems (this is called included bark).
Visible cracks, stress marks, or lean.
So, What Can You Do?
We work with many homeowners in Snoqualmie, Fall City, and Duvall who love their trees and the beauty they provide, while also wanting to keep them healthy and safe. Here are a few options depending on the tree's condition:
Keep an eye on the tree. Not all codominant trees are immediate risks, but monitoring them over time is smart.
Prune while the tree is young. If caught early, strategic pruning can help guide the tree into a better growth pattern.
Install cables or Braces. Structural support can reduce the risk of failure. Learn more about cabling and bracing on our blog here.
Consider the removal of the dangerous tree. If the tree is in poor health or poses a serious safety risk, taking it down might be the safest choice.
The Difference Between U-Shaped and V-Shaped Unions
You can tell a lot by the shape where the two leaders meet:
U-shaped unions have a wider angle, usually allowing more wood to form and creating a stronger connection.
V-shaped unions are tight and often trap bark—these are the ones that tend to split over time.
When to Call an Arborist
If you're in the Snoqualmie Valley, Sammamish, Issaquah, or nearby and unsure about a tree on your property, call us. We specialize in helping people understand what's safe to keep and what might need attention. A quick inspection can go a long way toward preventing big problems down the road.
At Rain City Tree Works, we're out in these communities daily, climbing, pruning, and ensuring trees are stable and strong—whether they're growing on a mountainside or in a backyard.
Codominant tops might look harmless, but they can turn into serious hazards if left unchecked, especially in the kind of weather we get around here. Whether you're caring for a big fir that's been growing for decades or a younger tree that just needs a little guidance, we're here to help you make a safe, informed decision.