University of Vermont Extension
Department of Plant and Soil Science
Anytime News
Article
POWER LINES AND TREES
Dr. Leonard Perry, Extension Professor
University of Vermont
Every summer during
thunderstorms, and every winter during snowstorms, I thank my power
company for
clearing the rights of ways near their power lines to prevent service
disruptions. Proper care and pruning of
trees on your property, as well as planting appropriate species in the
beginning, can keep you and your property safe and with fewer power
outages.
The most important point to remember if trees are already growing into
power lines, is to not prune them yourself.
Such lines, especially the main ones feeding each home, are often not
insulated. Touching or even getting
close to them could result in death.
Cutting branches that, when falling, could touch live lines should be
avoided as well, as these could cause short circuits or fluctuations
that
damage electronics. Alert your power
company to such situations and either let them do the pruning or
recommend
qualified arborists.
If your trees are reaching
towards the power lines, but not close yet, they should be pruned if
they’ll
eventually cause problems. Spring, as
growth is resuming, is the best time for such corrective pruning.
Of course you’ll need to know what the trees
are and how tall they’ll get when grown.
Your local nursery can usually help if you aren’t sure.
Some trees may be short, or fully grown
already, and never cause problems. There
is no need to prune these, unless for other reasons such as broken
limbs.
When pruning trees under power
lines, don’t shear as you might a hedge, or “top”
horizontally. These result in many smaller shoots that are
weak and can break in storms or wind, lead to rot organisms entering,
and
weaken the tree overall. If you employ a
tree service, make sure they wont use this outdated practice.
Two better practices for pruning
trees near power lines are the V-shaped and sidetrim methods. In
the former, used for trees directly under
power lines, branches are removed from the center. Side branches
then grow up in a V-shape on
either side of and away from the power lines.
In the latter, used for trees growing alongside power lines, branches
are removed only from the side that might interfere with the lines. For
either
method, prune branches back to a side limb or to where they come from
the
trunk, to avoid sprouting of many weak side shoots.
If, by pruning trees as above,
they are quite unsightly, it may be best to remove them all
together. Also remove fast growing trees, such as
willows, that will need frequent pruning.
Old trees, or those that are weak, should be removed as well.
Structurally weak trees may have lots of
rotten limbs waiting to fall, uneven shapes, and weak branch angles in
narrow V
patterns from the trunk.
Of course the best practice is to
not grow trees near power lines if none are currently present. If
trees are desired, often for screening or
aesthetics, then plant low-growing ones.
They should be under 25 feet tall at maturity if they’ll be
within 15
feet of power lines (as measured along the ground). Those trees
growing over 25 to 50 feet tall
should be planted at least 30 feet from power lines. Those
growing over 50 feet tall should be
planted at least 40 feet away.
Don’t plant under the smaller service lines
from the pole to your home, as these are often lower than the main
power lines.
Nor should you plant vines that will climb up power poles, or support
wires. Utilities often recommend
planting lower shrubs near poles, but not within about 10 feet.
If you want to screen unsightly poles and
wires, this is best done by plants nearer to where
they will be viewed, such as a porch or windows. Just make sure
and allow plenty of room for
growth if planted near buildings, walks, or other structures.
There are a several good small
trees or large shrubs to choose from for northern
landscapes. Crabapples are one of the most common small
trees, attractive with spring flowers and fall fruits, growing 12 to 25
feet
high depending on cultivar (cultivated varieties). Make sure to
look for disease-resistant
cultivars, and don’t plant if the fruits will be a nuisance if
dropping into
lawns or onto sidewalks.
Japanese tree lilac (Syringa reticulata) is another small
tree 15 to 20 feet high and 10 to 15 feet wide, having attractive bark
and
creamy white flowers in June. American
hornbeam (Carpinus caroliniana)
reaches about 25 feet tall and a bit less wide, with attractive bark,
spring
flowers, and fall color. Hawthorns are
often recommended, getting 15 to 20 feet high and 10 to 15 feet wide,
depending
on species. Make sure to get ones
without lethal thorns. Hedge maples (Acer campestre) are
dark green in summer
and gold in fall, but as they may reach slightly above 25 feet high and
wide
they may need some pruning.
Ornamental plums and cherries
generally reach 15 to 20 feet high and 10 to 15 feet wide, with very
beautiful
spring flowers. Just make sure to buy
ones hardy for your area. Purpleleaf
sandcherry (Prunus x cistena) only
gets about 8 feet high and slightly less wide, with white spring
flowers and
reddish purple leaves. Showy or European mountainash (Sorbus)
have attractive white flowers in June on trees 20 to 25
feet high, with bright orange or red fruit in fall.
Unfortunately, these may be short-lived due
to insects and diseases.
Large shrubs might be used
instead of small trees, just make sure they have room to spread if
needed. The native serviceberry (Amelanchier) has
attractive gray bark on multiple stems to 25 feet
tall and 10 to 15 feet wide, with white flowers in May and fruit
(edible by
birds and
humans) later in summer. The Siberian peashrub (Caragana arborescens)
is, as its name suggests, quite hardy. Yellow early summer
flowers appear on this
shrub reaching 10 to 15 feet high and 5 to 8 feet wide. Lilacs
reach 10 to 15 feet tall and wide,
with a range of flower colors most are familiar with in spring.
Saucer or star magnolias are
large shrubs with a rounded habit, generally 8 to 12 feet high and
wide, with
generally white or pink flowers in early spring. Native viburnums
have nice white flowers in
summer, followed by attractive fruits good for wildlife.
Depending on species they get 6 to 12 feet
high and similarly wide. Make sure to
choose viburnums that are resistant to the viburnum leaf beetle such as
the
doublefile, leatherleaf, or Siebold.
Whether trees or shrubs, if near
roadsides in the north, make sure they are salt tolerant, one of the
best being
the Japanese tree lilac. Avoid trees
that you may find sometimes recommended but that may be invasive, such
as amur
and tatarian maples, honeysuckle shrubs, or Russian olive. Check
your local nursery for more choices of
plants that are power-line friendly.
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