According to Bartlett Tree research laboratories
"Girdling roots are usually lateral roots at or
slightly below the soil line that cut into at
least one side of the main trunk. These
roots restrict water and nutrients, which
may be translocated to the leaves.
Branches will eventually become weakened
and the tree may die in five to fifteen years
from the girdling roots alone, or in
conjunction with environmental stresses or
attacks by insects or diseases. Cultural
practices like fertilization, irrigation and
pruning will not offset the slow growth
caused by girdled roots. Once diagnosed,
they should be treated promptly.
CAUSES AND PREVENTION
Girdling roots are caused by nursery and
transplanting practices, soil obstructions
and unknown factors.
When plants are held in containers for too
long a period of time, many roots begin to
circle around the pot. These
eventually can girdle the tree. When
planting trees and shrubs with this
condition, be sure to loosen these roots
from the container root ball and spread
them out in the planting hole before back
filling. Circling roots two or more years
old will be woody and may have to be cut
and removed from the root system, because
they will have taken the permanent shape of
the container and cannot bend enough
without breaking. Although this reduces
the size of the root system, it will prevent
the development of girdling roots in the
When a planting hole is not dug wide
enough or deep enough, bare-rooted stock
can be twisted into the hole in order to
make it fit. This undesirable practice can
cause root growth encircle the trunk and
Be certain to make planting holes wider
than the root area in order to prevent
encircling roots from forming.
The third major cause of girdling roots is
planting in very compacted soil, where the
new roots have difficulty growing out of the
planting hole and into the surrounding hard
soil. Roots can circle the bottom of the
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.
SYMPTOMS AND DETECTION
Trees which leaf out late, have small
chlorotic leaves or needles, drop their
leaves early, and are dying back should be
checked for a girdling root, particularly if
the normal flare or buttress swell is absent.
This condition is associated with placing
too much fill over the roots, a procedure not
uncommon in new housing developments.
Probably the most reliable aboveground
characteristic of a girdling root is a trunk
indentation of flattening or the base of the
bole. Non-girdled trees rarely show this
abnormal development. Note that not all
girdled trees show crown symptoms
commonly attributed to girdling roots.
Most girdled trees are not severely girdled,
with few roots ever circling more than 50%
around the bole. Since most girdled trees
are girdled by more than one root, careful
examination around the entire
circumference may be necessary. Species
like sugar, Norway maple, and white pine
particularly are prone to forming girdling
roots. Soil excavation is often needed to
find girdling roots.
A large majority of girdling roots is found
in the top several inches of soil, although
they can develop at a somewhat greater
depth. Frequently they can be seen on the
surface where erosion has removed one or
two inches of soil from around the base of
the trunk. Some girdling roots are present
at the soil line.
TREATMENT AND REMOVAL
A girdling root must be removed in a
manner that will minimize injury to the
trunk cambium beneath the root. First
excavate soil from around the root
uncovering the entire length to be removed.
Using a chisel or saw, cut the root at a point
6 – 12” out from the trunk. The final cut is
made where the root attaches to the trunk.
This prevents the root from
being pulled violently away from the
embedded area causing extensive cambium
injury if the root happens to be under
tension. This is important since
occasionally it is best to leave the girdled
root in the tree after cutting because the
trunk and cambium would be damaged
severely by gouging out the deeply
embedded root so that it does not grow
back together. Detach the root if it is not
embedded very deeply.
Prune deadwood, and if large roots were
removed, thin the crown to compensate for
the loss of roots. Very large girdling roots
should not be cut or removed."