The Ten Commandments of Tree
By Robert Cox, Colorado State University Cooperative Extension
Trees evoke all kinds of images. Arbor Day, Earth Day and the coming of
spring take care of that.
But, before we dream about their beauty and the cooling shade trees
supply through the summer, let's consider The Ten Commandments of tree planting.
Denver's dry climate and generally poor, alkaline soils present some
difficulties for trees. Healthy, long-lived urban trees get off to a good start when we
pay attention to some tree-planting fundamentals.
Here are guidelines to help ensure that the tree you buy and plant this
year will be part of your landscape in the years ahead.
For what reasons are you planting the tree?
You may want privacy, increased property values, a windbreak, shade, fall color, flowers,
fruit or a bird habitat. Perhaps you want to create a sound barrier. Combine this
information with knowledge about the site.
Site suitability will determine which, if any trees to plant. The
designated site may be in the lawn, near a patio, along a street or sidewalk, in a garden,
in sun or in a shaded spot. Soils may be clay, sandy, saline, compacted, wet or dry,
gravelly or even full of old building rubble. Whatever the situation, you will need to
determine if the site is suitable for growing a healthy tree.
Consider planting for energy conservation. Deciduous trees will shade
the west, south and east sides of the home in summer, and evergreen trees along the west
and north edges of the lot will provide winter windbreaks.
This is a good time to visit your local Cooperative Extension agent.
You can ask for fact sheets titled "How to plant trees and shrubs;" "Small
deciduous trees for privacy and color;" and "Large deciduous trees for street
You'll want to consider that fast-growing trees often are weak and
subject to storm damage. Think about the mature size and shape of trees and learn whether
their roots might invade sewer lines, lift and crack sidewalks or make bumpy lawns. Learn
which trees are likely to harbor insects or diseases.
Try to plant trees when the weather is cool,
cloudy and humid, but not windy. If you can't plant right away, keep the tree in a cool,
shady, protected spot and keep the roots moist. It helps to soak bare root trees and
shrubs in a bucket of water overnight before planting.
To prepare the site, mark a circle or square at least 3 times the
diameter of the tree's rootball. Excavate the area with a pick and spade. In clay soil,
dig to a depth 2-4 inches shallower than the height of the rootball. In
sandy soil, dig to a depth equal to the rootball. Leave the bottom of the
hole firm and undisturbed.
To the excavated soil, add 25 percent, by volume, of a coarse organic
amendment, such as sphagnum peat, compost or aged manure. Mix it well with the excavated
soil; this becomes your backfill.
Don't put fertilizer into the planting
hole; it may cause root injury. Next spring, fertilize young trees lightly.
Remove any plastic or metal containers from the rootball. Place the
tree upright in the center of the planting hole. If the tree is in a fiber pot, tear off
the sides. If the roots of a containerized tree are potbound, "tease out" some
of the roots and shallowly slit the rootball's sides with your finger or a knife.
For balled and burlapped trees, cut any rope tied around the trunk and
pull the burlap away. Cut any reinforcement wire, removing as much as possible, but be
sure the rootball stays intact.
Shovel backfill into the hole; continue until roots are covered and
most of the backfill is used. Don't tamp the soil with your feet.
Water the soil at relatively low pressure, using the
hose or a "bubbler." Let the water, not your foot, settle the soil. If the soil
settles below grade, add more backfill. When done, the planting area should be well-soaked
and moist backfill should barely cover the top of the rootball. Watering frequency depends
on the soil, not the calendar. Dig with a trowel on the edge of the planting area. Soil
that feels moist and holds together when squeezed doesn't need water. Overwatering drives
air from the soil, causing root suffocation. Frequent, light watering promotes shallow
root development. Mulching will reduce watering frequency.
Root stimulator solutions have negligible value. You can use them, but
they aren't necessary for transplant success.
A newly planted tree needs only minimal
pruning. Prune out only dead, diseased or injured branches. Research shows that
transplanted trees establish quicker when as much foliage as possible remains. If you do
prune, don't use pruning compounds on pruning cuts.
Send your trees into winter with a good supply of moisture by watering
them thoroughly in fall. Water during extended warm, dry periods of winter to prevent
drought damage to roots. This is especially important for trees planted the previous year.
STAKE SENSIBLY - Trees can be staked too tightly or for too long.
Don't stake small trees or those not in the wind's path.
Large evergreen trees, planted in a windy site, will need staking. To
stake,do not use garden hose and wire. Instead run wire through grommeted staking straps
or use wide strips of carpeting. This way, the straps, not the wire, passes around
the trunk. A year of staking usually is sufficient.
A forest tree provides its own mulch with
several inches of leaves on the ground. We can imitate this by mulching the planting area
with 3 to 4 inches of wood chips, chunk bark, straw, pine needles or shredded leaves.
Don't use plastic beneath the mulch; water or air can't penetrate it. Fabric-type
weed-barriers are preferable.
Rigid staking of a tree is counterproductive; research shows trees
don't develop normally if they're not allowed any sway.
Use crepe paper or other wraps on your deciduous
tree trunks about Thanksgiving time; remove the wraps around Easter. Do this for the first
2 to 3 seasons. This protects young trees from winter sunscald. If you've purchased a tree
with the trunk wrapped, remove the material now; otherwise the wrap could harbor insects
and diseases over the summer.
One thing you won't see in the forest is manicured lawns around a tree.
Research shows that newly planted trees are at a disadvantage when they must compete with
grass for water, air and nutrients. Keep grass from the planting area for at least one
year. If you mulch around trees, instead of planting grass, you also prevent possible
trunk damage by lawn mowers or string trimmers.
Photograph courtesy of Judy Sedbrook.
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