Selecting
Ornamental and Shade Trees for the Eastern Plains
Proper
landscaping elements can conserve up to 25% of the energy needed to
heat or cool a home or building. Using trees, shrubs, vines and man-made
structures can modify the climate around any building to reduce heat
gains in the summer and heat losses in winter. Protection from winter
wind and shading from summer sunlight can effectively reduce energy
consumption.
When
landscaping a home, sketch it and the lot to scale, allowing 1/8 or
1/10 inch per linear foot. Identify north (N) with an arrow. On the
plan, mark driveways, downspouts, utilities, fences, walkways, overhead
lines and obstructions, doors, windows and other glass areas. Measure
the height of the house. Observe the wind and effects of a winter
storm on your building. Note the direction of winter winds, usually
Northwest in origin, and add windbreaks of mostly evergreen trees
to your plan to block the prevailing wind. (See Landscaping
for Energy Conservation, no.7.225)
Observe
the sun during different seasons of the year. Notice how the sun strikes
the house in the early morning and late afternoon in the summer, and
between 9 a.m. and 3 p.m. in the winter. Add deciduous shade trees
to your plan to maximize summer shading and winter solar heating.
Avoid planting evergreens on the south and southwest sides of a home,
since they will block winter solar heat. Instead, plant evergreens
on the north and west sides of your property to slow the prevailing
winter winds and save on heating bills.
Choose
specific trees for your plan with an understanding of their mature
height and spread. The height of the structure you want to shade or
protect should be considered. A single story building surrounded by
medium to small trees appears aesthetically pleasing from a design
perspective. Also, the mature height of trees will determine the location
for maximum shading. Use small trees under utility lines and near
small buildings. Remember that evergreens can provide screening from
unsightly views and a sound barrier from traffic and loud noises,
as well as wind protection. Keep in mind that large shade trees require
large planting areas for the development of healthy root systems and
a mature canopy. Avoid planting spreading trees too close to structures.
Use
fences, windbreak plantings, and shade trees to provide a sun pocket
on the south side of your home, creating a warm spot for outside activities
during sunny, cool, but comfortable winter days. A sun pocket makes
an excellent location for a patio or greenhouse.
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Choose
your planting site carefully. Match the tree's desired function to
the cultural and environmental conditions of the site. These include:
soil conditions and pH, available light and exposure, water and adequate
drainage, localized weather patterns, terrain and elevation and the
presence of a microclimate (a location with climatic conditions different
from the surrounding geographic area). Choose trees that are well
adapted to Colorado's harsh, variable climate. Consider that some
trees are more suited to partial shade, low moisture and drought from
sprinkler system malfunctions and other changes that occur as a landscape
planting matures.
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Consider
the normal mature height and spread of trees for your site. Trees
with a slow rate of growth are generally thought to be more desirable.
Fast growing trees develop weak wood that splits and breaks easily
in storms, as in the snowstorm of September 1995. Consider the general
shape of the tree at maturity since upright forms can be more appropriate
for narrow spaces than spreading types.
Some
trees are evaluated for insect and disease resistance. Crabapples,
for examples, should be chosen for fire blight resistance.
Consider
other plant characteristics that make trees desirable, such as flowers,
fruit, fall color of leaves, winter texture in the landscape, exfoliating
or colorful bark, branching habit, more than one season of ornamental
interest and attractiveness to wildlife and birds.
Some characteristics make trees undesirable. Avoid planting trees
with weak wood unless used for quick, temporary cover only. If fast
growing, weak-wooded trees are used, plan to replace them with more
suitable species as soon as possible. Add man-made structures, like
arbors, to provide immediate shade. Beware of trees that are susceptible
to insects and diseases or that require high maintenance and frequent
pruning. Do not locate trees with excessive leaf, fruit or twig drop
next to gutters, sidewalks, patios or parking lots. Avoid weedy species
that become difficult to control in Colorado's environmental and social
conditions, since chemical herbicides are usually the only effective
controls. Never TOP trees to limit growth or control their size. Topping
trees "causes decay and sprout production, resulting in a potentially
hazardous situation once the sprouts become large and heavy" according
to the International Society of Arboriculture, the recognized authority
on tree health care.
When
selecting the plant in the nursery, always choose the best, healthiest
plant. Select a reputable Colorado nursery or garden center that stocks
trees acclimated to our growing conditions. Nursery-grown plants are
superior to "collected" plants of the same species, since containerized
plants are the least risky of all, as compared to B&B stock and bare-root
material. Choose only trees with good branch spacing and trunk taper.
Leaves, when present, should be evenly spaced along the twigs. Avoid
trees with many upright branches, rather than good horizontal growth.
Do not purchase trees that have injuries to the bark or with root
balls that are loose in the container, or have not been kept moist.
Avoid trees with circling roots that will eventually girdle the trunk.
Avoid trees with visible damage from insects or diseases.
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