LSU AgCenter Horticulturist
Land-grant universities, including Louisiana State University, are committed to advancing agriculture in America through research and innovative growing and farming methods. Another part of our mission is disseminating research information to the public. I recently had the opportunity to attend a training program focused on urban tree health, an initiative aligned with this mission, and I’m excited to share some of the great techniques we learned.
To ensure tree health in urban settings, we’ve got to start with the roots. One technique we learned about based on successful research is called root shaving. This technique can improve the health and success of the root of newly planted trees. The technique isn’t quite so new but has not been readily adopted by many home gardeners and landscape professionals.
Trees that are growing naturally in a forest form a broad network of six to 12 mostly straight, large-diameter roots that extend radially. These roots grow horizontally outward from the trunk. However, the trees we purchase from retail garden centers and wholesale nurseries have been grown in round containers that prevent this natural, radial, horizontal growth.
In containers, tree roots encircle the pot and extend downward to the bottom. This root structure can lead to tree instability and the development of an unusually deep root system, which is not well suited to compacted soil in urban landscapes.
Roots will continue to circle in the same pattern as they did in the container when planted in the ground if we do not take any action. The good news is it is simple to correct this circling of the roots by shaving, or removing, the outer ring of roots before planting.
The correction can be made by removing the outer 1/2 inch to 1 inch of the root ball's periphery, where roots are often matted or deflected due to container walls. You can do this by using a sharp digging spade or hand saw to trim peripheral roots in container-grown trees before planting.
New roots will form at the end of the cut roots. Once planted in the ground where they can perform their natural horizontal growth, the roots will establish a very strong system that will support the tree. Trimming the roots before transplanting encourages the development of new, healthier roots that can more effectively establish in the new location.
Root shaving is a simple practice that helps ensure the long-term well-being of the tree. Once rooted in, it can be extremely difficult to correct problems underground.
There are two other important things to do when planting trees from containers. First, it is a good practice to eliminate excess soil on top of the root ball down to the point where the first main roots originate, checking for circling roots near the trunk. Secondly, water the tree heavily after planting to encourage new growth. Ensure proper drainage and that roots are not in standing water for extended periods of time.
Lastly, apply a 2-to-4-inch application of mulch — but do not pile any mulch against the trunk and keep it off the root ball on newly planted trees. Spread mulch evenly underneath the canopy of the tree.
Tree roots play a crucial role in the overall health of trees and the soil ecosystem. They absorb water and nutrients from the soil, providing essential elements for the tree's growth and development. Stable root systems anchor the tree securely in the soil, providing stability against wind, rain and other environmental forces, and strong roots contribute to the overall structural integrity of the tree. Ensure the success of your trees by establishing a strong root system with root pruning before planting.
Root shaving or pruning can be done with hand saws and hand pruners prior to planting. Photo by Randy LaBauve/LSU AgCenter
Root shaving can help ensure the long-term well-being of trees. Photo by Randy LaBauve/LSU AgCenter
Roots of container-grown trees will continue a circling pattern if they are not pruned before planting. Photo provided by Ed Gilman
Roots of container-grown trees will spread in a natural, outward pattern if they are pruned before planting. Photo provided by Ed Gilman