I hope everyone had an enjoyable holiday season and is having a great start to the New Year. Let’s spend some time this month looking down at the roots. A common diagnosis I make on declining trees is girdling roots; unfortunately, many people have no idea what a girdling root is! Girdling roots are usually lateral roots at or slightly below the soil line that cut into the main trunk. These roots restrict the flow of water and nutrients and lead to tree decline (see photo above). Many different types of factors – some natural and others manmade, cause girdling roots, but the top three causes are:
* Leaving a plant in a container for too long
* Improper planting
* Compacted soil.
*By the way, Some trees have a genetic tendency to have the roots grow in a circular pattern.*
When plants are held in containers for too long a period of time, the roots begin to circle around the container. These eventually can girdle the tree. When planting trees and shrubs, be sure to loosen the roots from the root ball and spread them out in the planting hole before back filling.
Improper planting can also lead to girdling roots. When a planting hole is not dug wide enough or deep enough, bare-rooted stock is twisted into the hole in order to make it fit (not a good idea!). This undesirable practice can cause root growth to encircle the trunk and result in girdling of the main trunk. Be certain to make planting holes wider than the root area in order to prevent encircling roots from forming – remember: Put a 10 dollar tree in a 100 dollar hole. Also remember to remove all twine, wire and burlap from around the trunk (The photo below shows a tree with the twine left on at planting time)
A third major cause of girdling roots is planting in very compacted soil. Roots can circle the bottom of a compacted planting hole, not unlike those growing in an undersized container. Eventually, several of these roots can begin girdling the trunk. Other soil obstructions like foundations, curbs or large rocks can deflect roots and may contribute in some cases to the development of girdling roots.
Next time we will discuss how to diagnose and fix girdling root problems…