Symptoms of Girdling Roots
Symptoms include reduced growth, smaller-than-normal leaves,
fewer-than-normal leaves, lighter green leaf color, branch dieback
and the eventual death of affected trees. These symptoms are
frequently seen just on the side of the tree where the offending
root is growing. The trunk may look 'flattened' on that side, too.
Girdling roots do not become obvious until five to 20 years after a
tree is planted, and it happens so gradually that people often do
not realize there is a problem until it is too late.
Certain species of trees are more susceptible than others, including
maple (Acer spp.,
except silver maple), sweet gum (Liquidambar
styraciflua), magnolia, pine and linden (Tilia
spp.). This susceptibility can be compounded by poor site conditions
and poor planting practices. Street trees grown in tree pits that
are too small or trees growing in severely compacted soil are more
likely to have a problem with girdling roots. Trees that have been
planted too deeply or mulched too deeply are also good candidates.
Check Container Grown Trees
Container-grown trees and shrubs that are planted straight out of
the container without breaking their circling roots before planting
are very likely to develop girdling roots, too. On container plants,
score the rootball by cutting an inch deep into it from top to
bottom on at least four sides. You should also make two diagonal
cuts across the bottom of the rootball in an inch-deep "X" pattern.
Untangle badly circling roots by hand, and prune off those roots
that are circling so deeply back into the rootball that you cannot
untangle them. Some arborists recommend removing all artificial soil
from the roots of container-grown plants so you can clearly see the
circling roots and eliminate them.
Trees should always be planted so that the root flare -- where the
trunk flares out to meet the roots -- is just at ground level. If
your tree goes straight into the ground like a telephone pole, it is
planted too deeply. If you are planting a balled-in-burlap tree, do
not dig the hole until you find the root flare so you know how deep
to dig it. Untie the twine that holds the burlap around the trunk
and pull the burlap back so you can clearly see the top of the
rootball (do not remove the burlap completely until you have the
tree situated in the hole).
If you cannot see the root flare, remove soil around the trunk until
you can see it. You can use your hands, a hand cultivator or the
curved part of a wire coat hanger. The root flare can be several
inches deep, so be patient and work gently until you find it. You
will break some fine roots as you do this. They are known as
adventitious roots and can become girdling roots in the future
unless the tree is re-planted at the proper depth.
Once you find the root flare, dig the hole so that it will be at
ground level once the tree is planted. The hole should be two or
three times as wide as the rootball. Backfill with the soil you dug
out of the hole. Amending the backfill with a lot of organic matter
is no longer recommended.
planting directions apply to container-grown plants, too. The main
difference is that you can build a cone of soil in the bottom of the
hole and splay the slashed rootball over it as additional insurance
against girdling roots. If you do not remove the artificial soil, be
sure it is completely covered with a thin layer of native soil.
Otherwise, that artificial mix will dry out much faster than the
surrounding soil. Thoroughly soak the rootball close to the plant
and the surrounding soil when you water to prevent drought stress.