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Identify and treat girdling roots on shade trees

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

future.

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

produce girdling.

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."

 

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