University of Vermont Extension
Spring, Summer News
Department of Plant and Soil Science
SELECTING THE BEST TREES
Dr. Leonard Perry,
University of Vermont
Trees are the first plant consideration in
most landscapes, form the framework or base to build on and around,
affect subsequent plantings. Trees are a
major investment, most lasting a lifetime and perhaps longer than
plant them, so the selection of the right tree for the right place
is a major
decision. This applies whether you’re building a new landscape, or
replacing a tree that died from age, damage, disease, or other
the best tree for a site depends on what you desire from the tree,
its quality, and a proper match to the site. According to a
brochure from the International
Society of Arboriculture (ISA) on Tree Selection, the main cause of
is not from pests and diseases, but from planting the wrong tree.
you start shopping for a tree, consider what you want from it. Will
it be for aesthetics? If so, what are its shape, growth habit, rate
of growth, flowers, fruit, or attractive bark?
You’ll hopefully be living with this tree for some time, so personal
preferences are important and will vary with individual.
your tree be for an environmental use such as providing shade,
providing wildlife food or habitat, reducing noise, or just adding
oxygen? Evergreen trees provide a
backdrop for other plantings, screening from wind, and food or
wildlife in winter. Trees along streets help reduce pavement glare
runoff, and filter pollutants from vehicles.
consider where the tree will go, and the space for its ultimate
growth. This is perhaps the most misjudged or
overlooked decision in buying and planting trees, with them ending
up too close to buildings or other plantings, or
too tall under utility wires. Or they
may block desired views and need frequent pruning, or be of an
shape. Choose the right size and shape
of tree, and maintenance will be greatly reduced. You even may end
up deciding you just don’t
have room for even a small tree—which is perhaps better than
planting one and
having to deal with the size in a few years.
Consider aspects of the environment, such as
hardiness, soil type, and if a small tree if it will be shaded by a
taller trees. Often hardiness is given
as a USDA zone, referring to average low temperatures, with maps
catalogs, on labels, in books or online
type is critical, as trees just can’t be moved easily as can smaller
flowers. Poor soil drainage will starve
the roots of oxygen, drowning them and leading to root rots. If
you’re unsure about this, dig a hole a
foot deep and fill it with water. If the
water doesn’t drain away in 6 hours, you may have a problem and
a landscape professional or tree specialist. Or you should choose a
can tolerate “wet feet”.
compaction from foot or vehicle traffic can keep water and air from
the soil as well, resulting in tree decline or death. Keep in mind
that tree roots extend out at
least as far as the tips of the branches, or “dripline”, so this
planned for in tree growth if they’re to be in areas of potential
many trees will tolerate some level of pests and diseases, and in
on trees provide a huge supply of food for birds, there are some
you should think about or ask your nursery professional for their
recommendations. Crabapple trees, for
instance, have varying levels of resistance to scab disease,
cultivar (cultivated variety). With the
emerald ash borer insect in many areas of the country, you may want
to shy away
from ash trees. Mountain ash and some
apple trees easily get fireblight disease.
all these considerations have been made prior to even starting your
shopping. So when you do visit a plant
outlet, nursery, or garden center, look for the best quality trees.
Just as trees are a long-term investment,
injuries you may start with on trees (just as ones that happen
later) may take
a year or more to show symptoms.
looking at trees to purchase, the ISA says to keep in mind R.I.F.
This is a way to remember to inspect a plant
for problems with roots, injuries, or form.
Make sure the tree has plenty of roots to support the top—the larger
top, the larger the pot or “root ball” if a ball of burlap holding
roots often are a major problem with trees purchased through large
stores, and even some nurseries. Trees
are potted “bare root” in spring by growers—just the plant dug with
no soil, or
from cold storage. You then buy the
plant which is starting to grow on the top, or in full leaf, but
with few if
any roots formed yet. This causes stress
when planting and subsequently, and can easily result in decline or
check roots in pots, turn them on their side and tap the sides.
Pulling the trunk gently, the roots and soil
should easily pull out together. If the
plant starts to pull out, leaving soil behind, put it back and move
plants in pots or a root ball seem well rooted, look at the base of
for any roots that are tight and circling the trunk or rubbing
against it. These “girdling roots” are from improper
growth, or plants in pots too long, and will eventually strangle the
is a common cause of tree decline in later years in landscapes.
the trunk and stems for injuries, either broken branches or trunk
wounds. Branches pruned off should not have stubs
left, as these lead to improper healing and diseases. If trunks are
wrapped with paper or a tree
guard, check under this as it often can hide injuries from improper
handling, or insects. Look for cracks in the trunk below branch
unions. Sunken and discolored areas on trunks may indicate start of
canker disease, so avoid trees with these.
the tree form as well—there shouldn’t be too many branches on one
side and not another, branches should be well-spaced around and up
the trunk, branches should not be rubbing or squeezed together, and
V-shaped angles between branches are weak areas that often result in
breaking off. If you want a
tree with multiple trunks, as is common in birches, choose one with
well-apart at the soil surface.
buying trees in spring, particularly before leafed out fully, make
are what the label states. A friend
bought a tree from a chain outlet, the tree labeled as a pear but
when it leafed out it obviously was a peach that wouldn’t have
survived a winter! Thankfully the store
had an easy return policy, but it was extra work to dig up the plant
it to the store.
want a particular cultivar of tree, this may be more difficult to
purchase time. It may take several years
for a form to develop, as in a sugar maple I bought thinking it was
the usual rounded
species. It turned out years later to be
more columnar, which actually fit my site better, fortunately. The
best way to get the correct plant is to
buy from a reputable nursery.
through these steps in planning for your new tree, then selecting
one of high
quality, you should be rewarded with one that grows well and gives
years of enjoyment. Trees in the
landscape also will increase the value of the property, should you
sell it and move. You can learn much
more on choosing and care of trees online from the ISA