Download Girdling Roots: A Problem of Shade Trees Trees can slowly weaken

Delbert Johnson
Doctor of Stumpology
Girdling Roots: A Problem of Shade Trees
Trees can slowly weaken and die over a period of several years by the strangling or girdling action of roots.
Some tree roots that begin to grow around or along the main trunk and large lateral roots can cut off or
restrict the movement of moisture and plant nutrients into the
SYMPTOMS: Over a period of time, branches on the sides of the
tree affected by the girdling root will slowdown in growth. Injury may
eventually show up as weakened top growth, short terminal twigs, and
smaller, lighter green leaves. The branches will eventually become
weakened by strangulation and the tree may die over a period of 5 to
15 years. Good cultural practices of fertilization, watering, and
pruning will not offset the slow death by girdling roots.
Figure 1. Normal tree trunk
Normal trees have a flare or buttress root swelling at the base of with flare or buttress at soil
the trunk as shown in Figure 1. Tree trunks without flare that grow line.
straight up from the ground as if a soil fill has been placed around
the tree can be suspected of having girdling roots as illustrated in Figure
2. Trunks of trees with a flat side or concave depression at the ground
surface instead of a swelling may also have a girdling root as seen in
Figure 3. Positive diagnosis of girdling roots below ground can be made by
carefully digging away the soil around the base of the tree to expose
Figure 2. Girdling root.
the encircling roots.
Trunk may grow straight up.
CA USE: The development of girdling roots on trees is usually the
result of unfavorable conditions which prevent the roots from
growing in a normal spreading manner. For example, the roots of
container-grown plants will grow out to the sides and then spiral and
coil around the side and bottom of the container. If the trees are
grown in the container too long, they become root-bound. In
transplanting container-grown trees or shrubs that are root-bound, 3
or 4 slits should be made down the sides of the root ball with a knife
or pruning shear, and then the roots should be spread out by hand. If
the encircling roots are not cut and straightened out, they will Figure 3. Girdling root
caused by obstruction such
eventually girdle, or strangle, the stem of the plant.
as curb, sidewalk, wall or
SOLUTION: Positive diagnosis of girdling roots is important since compacted soil.
other factors can cause the same symptoms. Girdling roots can be found growing from the soil surface to
a depth of a couple feet. The exposed girdling root often can be cut from the trunk or lateral root at the
point of attachment with a chisel and mallet. Several inches of the girdling root should be removed to
prevent it from growing back together. If there are many girdling roots, the removal process should be
gradual, perhaps taking two to three years. This allows new roots to develop and replace those that had
been supporting the tree with water and nutrients. After the girdling roots are removed, weakened trees
may respond with improved growth if careful pruning, watering, and fertilizer applications are used.