Trees are long term investments. Like a vehicle selecting the right one for you is a important step, and what is hidden can often lead to a lot of grief. The tree’s roots are one of the most critical parts of the tree. However, they are hidden by the pot and soil. Roots anchor, stabilize, and absorb water and nutrients. Unfortunately, nursery grown trees, especially those grown in pots, can have defects that inhibit proper root development. This blog post will address the importance of looking for defects, the importance of root pruning, and when you should return a tree.
As depicted above, the natural tendency of a trees root system is to first go down and then spread horizontally. The roots that go down secure the tree in place and the root spreading to the side keep it from toppling over. Nutrients are absorbed by the spreading roots within the top 6-12 inches of soil.
The most common problem seen in potted trees is circling roots. Circling roots occur when the tree is keep in pot too long. Often this is a result of large stocks or timing. Some trees grow roots faster than others and it can be difficult for a nursery to keep up. Unfortunately, either due to improper training or time restraints some nurseries take a badly root bound tree and pots it up without taking care of the problem (see Picture 2).
When trees have the circling root problem, such as the one displayed in photo 2, the tree will not develop stabilizing roots and will continuously fall over. If you find circling roots that are about the width of your thumb, then you should take the tree back for an exchange or a refund. These trees can become a major issue if they do survive. Planting the tree deeper is also not going to solve the problem and will ultimately cause other issues.
Like circling roots, Descending roots are roots that are growing out from the tree. When they hit the side of the pot instead of growing left or right, they grow vertically. These roots will never straighten out and stabilizing roots will not form. This could lead to a tree falling over.
Girdling roots are circling around and often against the trunk of the tree. If left unchecked these will eventually strangle the tree. Like circling roots, this is a result of the tree being in a small pot for too long. There are ways to correct this issue, even on established trees. In extreme cases, as shown in Photo 3, are best returned to the nursery.
In both of these defects it is best to at least remove the top layer of soil to see what the upper roots are doing. Often you may ask the nursery if you can take a look at the root system before you purchase the plant. A mark of a good nursery is they will allow you to take a peek.
It is not uncommon for any plant to be slightly root bound. It is just important to know the difference between the time to rehabilitate the tree and when to return it.
When taken out of the pot, most trees will have some circling or descending roots. Do not attempt to break up the root ball to spread them out. Normally they will continue to circle around the tree, rather than spread out. Instead, it is best to prune the circling and descending roots. Depending on the severity, this can be achieved with either a hand pruner, a handsaw or a saws-all. If you see only a few roots just clip them at the point where they come out of the soil. You want to see the circle of the root. If there are a large quantity of circling roots take the saws-all and shave about 3/4 to 1 inch of soil off the edge of the root ball. Then cut off about the same amount from the bottom of the root ball. Water the tree often for the first 4-6 months depending on the size of the tree. During this time new roots will form to secure the tree.
Any girdling roots that are close to the trunk or are crossing over another larger root, they can also be pruned off. To achieve this, carefully use a handsaw or a pruner to cut off the root. Be careful not to damage the trunk or the crossing root while pruning off the problem root.
Roots are important in the health of the tree. Defects such as gridling and circling roots can cause the tree to decline and often die. However, by taking some time to inspect the root system and to prune away any structural issues you can have a healthy tree that will last for many years. Circling, descending, and girdling roots are a major problem that can affect the stabilization and longevity of the tree. Pruning these defects now, rather than later, is one step in giving you a healthy and long-lived tree
- Container production practices: roots – Website by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida
- Cut roots at planting – Website by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida.
- Video: Shaved vs. Not Shaved – 11.5 minute root pruning demonstration video by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida.
- Video: Root Growth Shaved vs. Not – 1.5 minute video by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida.
- Removing Circling Roots – Guidelines on removing circling roots from established trees- Website by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida.