Maureen Sexsmith-West
ISA Certified Arborist, PR4600A
The most important and least considered part of your tree is the root system.
The root system of your tree will be extensive (several times wider underground that then tree is tall). The majority of these roots are absorbing roots that occur 6-12 inches below the surface. The structural roots which are the branches underground, grow as the support system to the tree.
Development of girdling roots is not well understood but is normally thought to be the result of unfavourable conditions which prevent roots from growing out in a normal spreading manner. Roots will only grow where there is optimum conditions to do so – they need oxygen and nutrients. When they meet an obstruction they will attempt find the path of least resistance. This can sometime result in ‘doubling back’.
A good example is a container-grown plant, where the roots are often forced to grow in a circular fashion (memory). If these trees are not pruned at the time of transplanting, this growth pattern can cause girdling roots.
Normal trees should have a gentle flare or widen at their base.
Trunks that grow straight up from the ground as though they were a telephone pole can be suspected of having girdling roots. In some instances the girdling root is visible. This can also indicate that the tree has been planted too deep.
Trunks with a straight side or a concave depression on one side may also have a girdling root. The wood is not able to expand in proportion to the rest of the tree.
Girdled Root at Surface
The presence of suckering on some varieties of trees can be an indicator of root issues.
Girdled roots due to restricted growth area by cement frame border
No root development due to failure to remove burlap, basket and twine
Detail of failed tree – abnormal root system
Girdling by steel grate – despite some effort to cut part of it away after it was too late.
