Caring for Tree Roots: Stem Girdling Roots

There are a wide variety of tree health care issues that arborists deal with above ground. However, it’s easy to forget that there is just as much plant material below ground as is above ground. And that underground portion (the roots) is just as important (maybe even more important) when it comes to overall tree health. The difficult part though, is that we can’t easily see what might be going on that could be affecting tree health.

There are many root system issues that need attention in tree care. More often they relate to soil based issues, but a big one is Stem Girdling Roots (SGR). Stem Girdling Roots refers to a common problem with urban trees where the roots up near the stem of the tree grow in circles under the soil and over time will girdle or ‘choke off’ of and eventually kill the tree. It often happens with trees that have been planted too deep, with mulch piled up too high around the trunk, or trees that were in pots too long before they were planted.

Knowing whether you may have SGR or not will take the skill of an experienced arborist by doing a process known as root collar excavation. The process involved using a pneumatic tool  (Air Spade) to remove the soil from around the tree and roots to expose the roots without damaging them with mechanical tools. In other words, we use highly compressed air to blow away the dirt. This allows the arborist to see if there is a problem with the roots and determine if pruning is needed. The Air Spade is also very useful in decompacting and aerating the soil within the tree’s critical root zone.

Canopy symptoms of SGR will typically present with the very top center part of the canopy dying back or thinning. Certain trees will also start presenting early fall color in those top center portions of the tree. Other indications can be dead spot on the side of the lower trunk with a lack of a clear flare to the base of a tree. The lack of a flare at the base of a tree (root flare/pedestal flare) is not necessarily an indication of SGR, but it does often indicate a tree that has been planted too deep which can lead to tree health issues on its own.

If left undiagnosed or untreated, SGR’s will eventually kill the tree. In my experience with trees expressing symptoms of SGR, about half the time the damage from the girdling roots is too far progressed to fix. Therefore, I recommend that you have all your trees evaluated by a Certified and qualified arborist in plant health care to notice any signs of SGR before the problem is uncorrectable. You can avoid SGR by; carefully and properly planting new trees making sure they are not too deep in the ground, mulch the areas around the base of trees with a level 2-4 inches of mulch and avoid piling the mulch up next to the trunk, and refuse trees that have been in pots more than a year or that already have circling roots in the pot or root ball.

Caring for trees and the soil around them is an often overlooked but important part of tree healthcare. As I stated earlier, we can use the Air Spade to aerate the soil around your tree. So often time the service can be used to investigate potential root system problems while providing a huge benefit to trees by improving the soil conditions that they are growing in. If you have a tree that seems to be declining, contact a qualified plant health care arborist and make sure a thorough evaluation is done to the root systems and well as the canopy in order to properly diagnose the issue.