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Tree selection is one of the most important investment decisions
a home owner makes when landscaping a new home or replacing
a tree lost to damage or disease. Considering that most trees
have the potential to outlive the people who plant them, the
impact of this decision is one that can influence a lifetime. Match
the tree to the site and both lives will benefit.
The question most frequently asked of tree care professionals is
"What tree do you think I should plant?" Before this question can
be answered, a number of factors need to be considered. Think
about the following questions:
• Why is the tree being planted? Do you want the tree to provide
shade, fruit, or seasonal color, or act as a windbreak or screen?
Maybe more than one of the above?
• What is the size and location of the planting site? Does the
space lend itself to a large, medium, or small tree? Are there
overhead or below ground wires or utilities in the vicinity? Do
you need to consider clearance for sidewalks, patios, or
driveways? Are there other trees in the area?
• What type of soil conditions exist? Is the soil deep, fertile, and
well drained or is it shallow, compacted, and infertile?
• What type of maintenance are you willing to provide? Do you
have time to water, fertilize, and prune the newly planted tree
until it is established or will you be relying on your garden or tree
service for assistance?
Asking and answering these and other questions prior to
beginning the selection process will help you determine the
"right tree for the right place."
Tree Function
Trees make our environments more pleasant. Properly placed
and cared for, trees increase the value of our real estate. A large
shade tree provides relief from summer's heat and, when
properly placed, can reduce summer cooling costs. An
ornamental tree provides beautiful flowers, leaves, bark or fruit.
Evergreens with dense, persistent leaves can be used to
provide a windbreak or a screen for privacy. A tree that drops its
leaves in the fall allows the sun to warm a house in the winter. A
tree or shrub that produces fruit can provide food for the owner
and/or attract birds and wildlife into your home landscape. Street
trees decrease the glare from pavement, reduce runoff, filter out
pollutants, and add oxygen to the air we breath. Street trees also
improve the overall appearance and quality of life in a city or
neighborhood.
Form and Size
Frank Lloyd Wright, the famous architect, once made the
comment, "form follows function." This is a good rule to
remember when selecting a tree. Selecting the right form (shape)
to complement the desired function (what you want the tree to
do) can significantly reduce maintenance costs and increase the
tree's value in the landscape. When making a selection about
form, also consider mature tree size. Trees grow in a variety of
sizes and shapes, as shown below. They can vary in height from
several inches to several hundred feet. Select a form and size
that will fit the planting space provided.
Depending on your site restrictions, there are hundreds of
combinations of form and size to choose from. You may choose a
small spreading tree in a location with overhead utility lines. You
may select a narrow columnar form to provide a screen between
two buildings. You may choose large vase-shaped trees to create
an arbor over a driveway or city street. You may even determine
that the site just does not have enough space for a tree of any
kind.
Site Conditions
Selecting a tree that will thrive in a given set of site conditions is
the key to long-term tree survival. The following is a list of the
major site conditions to consider before selecting a tree for
planting:
• Soil Conditions
• Exposure (sun and wind)
• Human Activity
• Drainage
• Space Constraints
• Hardiness Zone
Soil Conditions. The amount and quality of soil present in your
yard can limit planting success. In urban sites, the topsoil often
has been disturbed and frequently is shallow, compacted, and
subject to drought. Under these conditions, trees are
continuously under stress. For species that are not able to
handle these types of conditions, proper maintenance designed
to reduce stress is necessary to ensure adequate growth and
survival. Many arborists will, for a minor charge, take soil
samples from your yard to test for fertility and pH (alkalinity or
acidity). The tests will be returned with recommendations on ways
to improve poor soil conditions with fertilizers or soil
amendments (sand, peat moss, or manure) and will also help your
local nursery or garden center recommend tree species that will
do well in the soils found on your site.
Exposure. The amount of sunlight available will affect tree and
shrub species selection for a particular location. Most woody
plants require full sunlight for proper growth and flower bloom.
Some do well in light shade, but few tree species perform well in
dense shade. Exposure to wind is also a consideration. Wind can
dry out soils, causing drought conditions, damage to branches
and leaves during storms, and actually uproot newly planted
trees that have not had an opportunity to establish root systems.
Special maintenance, such as staking or more frequent watering,
may be needed to establish young trees on windy sites.
Human Activity. This aspect of tree selection is often overlooked.
The reality of the situation is that the top five statistics related to
tree death are caused by people. Soil compaction,
underwatering, overwatering, vandalism, and the number one
cause - planting the wrong tree, account for more tree deaths
than all insect and disease-related tree deaths combined.
Drainage. Tree roots require oxygen to develop and thrive. Poor
drainage can remove the oxygen available to the roots from the
soil and kill the tree. Before planting, dig some test holes 12"
wide by 12" deep in the areas you are considering planting trees.
Fill the holes with water and time how long it takes for the water
to drain away. If it takes more than 6 hours, you may have a
drainage problem. If this is true, ask your local garden center for
recommendations on how to correct the problem, or choose a
different site.
Space Constraints. Many different factors can limit the planting
space available to the tree: overhead or underground utilities,
pavement, buildings, other trees, visibility - the list goes on and
on. Make sure there is adequate room for the tree you select to
grow to maturity, both above and below ground.
Hardiness. Hardiness is the plant's ability to survive in the
extreme temperatures of the particular geographic region in
which you are planting the tree. Plants can be cold hardy and/or
for southern regions, heat tolerant. Most plant reference books
will provide a map of hardiness zone ranges. Check with your
local garden center for the hardiness information for your region.
Before you make your final decision, make sure the plant you
have selected is "hardy" in your area.
Pest Problems
Insect and disease organisms affect almost every tree and shrub
species. Every plant has its particular pest problems, and the
severity varies geographically. These may or may not be life
threatening to the plant. You should select plants resistant to
pest problems for your area. Your local ISA Certified Arborist,
tree consultant, or cooperative extension agent can direct you to
information relevant to problem species for your location.
Species Selection
Personal preferences play a major role in the selection process.
Now that your homework is done, you are ready to select a
species for the planting site you have chosen. Make sure you
utilize the information you have gathered about your site
conditions, and balance them with the aesthetic decisions you
make related to your personal preferences. The species must be
suitable for the geographic region (hardy), tolerant to the
moisture and drainage conditions of your soil, resistant to pests
in your area, and have the right form and size for the site and
function you have envisioned. Remember, that beautiful picture
of the tree you looked at in the magazine or book was taken of a
tree that is growing vigorously because it was planted in the right
place. If your site conditions tell you the species you selected will
not do well under those conditions, do not be disappointed when
the tree does not perform in the same way.
If you are having difficulty answering any of these questions on
your own, contact your local ISA Certified Arborist, tree care
professional, garden center, or county extension agent for
assistance. Their assistance will help you to plant the "right tree
in the right place." It is better to get them involved early and
make the right decision, to avoid having to call them later to ask
them if you made the wrong decision.
For Additional Information
This brochure is one in a series published by the International
Society of Arboriculture as part of its Consumer Information
Program.
