A.
Tree roots cannot break their way into intact sewer lines -- not
even weeping willows. The problem occurs when old terra cotta pipes
crack or develop leaks at the joints. The roots of almost any tree
will take advantage of the situation and could wind up clogging the
lines. This is much less of a concern in newer developments because
now builders use PVC pipe, which is much less likely to crack and
invite an invasion of roots.
Most tree roots are confined to the top twelve to fifteen inches of
the soil, where there is adequate moisture, oxygen and nutrients to
support a tree's growth. The fine, hair-like feeder roots
responsible for absorbing water and nutrients from the soil extend
out two to three times the reach of the branches (also known as the
tree's dripline).
We used to believe that tree roots were a mirror-image of the top of
the tree, but research has shown that tree root systems are much
shallower and broader spreading than that.
Smaller trees such as crabapple (Malus spp.), Japanese maple
(Acer palmatum) and 'Winter King' hawthorn (Crataegus
viridis), or large shrubs such as bottlebrush buckeye (Aesculus
parviflora), quince (Chaenomeles spp.), and blackhaw
viburnum (Viburnum prunifolium) would have less extensive
root systems than very large trees such as Norway, silver or sugar
maples (Acer spp.), willows (Salix spp.) or oaks (Quercus
spp.). Willows and Silver Maples are sometimes called 'water
seekers.'
You should be more concerned about doing a thorough assessment of
your planting site so you can chose trees that will grow well in
those conditions. The factors to consider should include:
• How much sun
or shade they will have to tolerate.
• Soil texture
and structure. Is your soil compacted clay or clay subsoil, or is
there some topsoil?
• How well the
site drains. Does water pond on the surface after a rain?
• Does the site
maintain adequate soil moisture or does it tend to dry out quickly?
• Will the
trees be exposed to road salt?
• Are they near
concrete sidewalks, driveways or buildings with concrete foundations
or mortar joints? Calcium carbonate leaches out of concrete and may
raise soil pH (the measure of acidity or alkalinity) to a range that
limits your ability to grow trees that prefer an acid soil. These
include maples, oaks, dogwoods, magnolias, conifers, and
broad-leaved evergreens such as rhododendrons and hollies.
• Exposure to
wind, especially in the winter. Wind is hardest on broad-leaf
evergreens.
Once you have
assessed the planting site, then you can narrow the list of
possibilities to those tough, durable trees that do not have major
insect or disease problems that would require your constant
attention to keep your chosen plants healthy.
Here is a brief
list of Web sites to help you choose plants that will tolerate the
conditions in your yard:
Plants for Wet
Sites
•
consumerhorticulture.psu.edu/pdfs/plants_wet_sites.pdf
Plants for Dry
Sites
•
consumerhorticulture.psu.edu/pdfs/plants_dry_sites.pdf
Plants Tolerant
of Shade
•
consumerhorticulture.psu.edu/pdfs/shade_tolerant_plants.pdf
Plants Tolerant
of Road Salt
•
www.treeboss.net/salt-tolerant_trees.htm
Plants Tolerant
of Clay Soils
•
www.extension.umn.edu/projects/yardandgarden/ygbriefs/h408claysoil.html
MORE
Sandy's
Tree Tips
|
