Even if you can't give a detailed explanation about the various parts of a tree's anatomy, you're sure to know the basics. The roots are below ground and grow downwards, with the branches and leaves above ground and growing upwards. But sometimes a tree doesn't follow these basic expectations. When a tree's roots begin to grow upwards, this is known as girdling, and can be bad news for a tree.
An Upward, Circular Growth
Girdling is evidenced when a tree's lateral roots (which should extend horizontally outwards from the tree's main root structure) grow upwards and begin to encircle the tree's trunk (quite literally girdling the tree). This development places pressure on the trunk and prevents the tree from being able to extract nutrients from the soil, as well as restricting the tree's ability to absorb water.
A Slow Process
Girdled roots are a slow process, and it's one that may be underway for many years before the tree is actually in jeopardy. It's often caused by the initial placement of the tree. If the tree is planted too deep, its access to nutrients is compromised, and the development of girdled roots is the tree's failed attempt to feed itself. Alternatively, if a tree was held in a nursery pot for an extended period of time, its root system will begin to encircle the trunk due to a lack of available growth space.
Whatever the cause may be, the bad news is that once root girdling has made its way to the surface, the tree's outlook is not favourable. The best way forward will depend on the tree itself. For smaller trees with moderate girdling, an arborist might suggest removal of the girdled root. This is traumatic to the tree, but with diligent care, it might recuperate and begin to thrive. With larger trees whose nutritional needs are greater, it can already be too late. In many cases of girdled roots, tree removal will be the only solution.
The loss of a tree from your backyard (particularly a mature one) can fundamentally change the aesthetics of your view, so if a tree with girdled roots has to be removed, consider installing its replacement during the same procedure, when the soil is aerated. You must be sure that the tree is planted at the most appropriate depth for its type and ultimate size, as this is the best way to prevent girdled roots.
While girdled roots often lead to the loss of a tree, it's important that you don't delay taking action. As the tree's trunk becomes more girdled, its health can deteriorate, making the tree pose a threat to its surroundings as it begins to die.