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Selecting Ornamental Trees
Trees are an important part of our environment; cooling our cities, cleansing the air, recycling oxygen, and reducing noise levels. In addition, plants enhance the quality of life by providing habitat for desirable wildlife and creating a restful environment for us.
Most of New Mexico is grassland or desert. Less than one‑third of the state is forested. Thus, trees planted in our cities and around our homes grow under climatic and soil conditions that may not naturally support tree growth. New Mexicans need trees which tolerate our soils and climate. Many of the trees are not native to New Mexico; however, they will adapt and thrive with appropriate care.
Selecting a Tree
The first consideration when selecting a tree should be the function of the tree in the landscape. This will determine where it is planted and which tree is chosen. Trees may be chosen for their shade, flowers, autumn leaf color, fruit, wildlife habitat, size, and form. Rate of growth is also a consideration, but should not be the primary reason for selecting a tree. Trees which grow rapidly tend to have a short life and create hazards because they often have weak wood and increased disease and insect problems. Trees should be considered a long term investment as a well‑placed, attractive part of the landscape which can add thousands of dollars to the property value in addition to the environmental benefits they provide.
When choosing a tree for the landscape, it is important to consider the location in which the tree will be planted. Mature tree height and spread should be considered in association with site selection; power lines, eaves, distance from structures, roads, walkways, walls, and other paved areas are factors which must be considered. If planted in the wrong place, such as near or under power lines, trees will interfere with power line maintenance, and traffic flow. Poor site selection will eventually lead to structural damage which will necessitate removal of the tree or pruning which will damage the form, function, and value of the tree. This can be avoided by matching the tree to the site. If you desire a specific tree, be sure to find a site appropriate for that tree. If your concern is a specific site, select a tree appropriate for that site. Many tree problems in New Mexico result from a failure to match trees and sites.
An unseen potential problem is the root system of a growing tree. The root system of an established tree will expand beyond the dripline of the tree. Trees planted close to walkways or other pavement can cause uplifting of the pavement due to root growth. Roots can clog sewer or septic lines. Most of the tree's roots are in the surface 18 inches of soil. However, the roots can spread a distance 1.5 or more times the height of the tree from the trunk. Thus, a 40 foot tree can have roots exploring soil 60 feet or more beyond the trunk. As a general rule, most of the large roots which cause structural damage will be found under the canopy of the tree at maturity.
Smaller, less destructive roots extend much further. These roots absorb water and nutrients. Homeowners must irrigate and fertilize well beyond the 'dripline' to adequately care for trees. The homeowner should anticipate the future size of the tree (above and below ground) in the landscape.
Another way to avoid problems is to choose trees adapted to the soil and climate. Soil conditions which must be considered include: depth, drainage, caliche layers, texture, pH, and salinity. Problems resulting from these factors can often be avoided by knowing the soil conditions and selecting trees adapted to these conditions.
A final consideration is selection of trees adapted to planting zones in New Mexico. These planting zone guidelines are based on climatic conditions under which the trees must grow. However, these guidelines do not consider microclimates due to changes in elevation over short distances and location relative to structures. Sites near the zone boundaries should expect harsh conditions more often than areas farther from the zone boundaries. Under weather conditions experienced in New Mexico, extreme weather will sometimes result in damage or death of the trees. However, planting by the zones should minimize the risk of tree death due to climatic stress. Some tree species may suffer winter injury from severe winter storms. However, this should not discourage experimentation in the landscape. The unique beauty of a tree could be enjoyed for many years, even if the tree is eventually replaced. Often, trees can reach maturity and provide enjoyment during the period between severe freezes. Additional information can be obtained from your nursery professional.
The trees listed are not intended to be comprehensive. This list is intended to provide guidance in selecting trees, identifying their positive and negative characteristics, and offering suggestions on where these trees can be planted safely. Do not let this list discourage the use of other tree species that are interesting. They may do well in the care of a concerned home owner.
Acer saccharinum. Silver Maple.
Acer saccharinum fact sheet The silver maple was once considered the best of
the maples for New Mexico. It is a fast growing, with narrow crotches and as
with all fast growing wood it is week and easily broken by wind storms. It is a
spreading tree that reaches a height of 50 feet or more. Its leaf has the
typical maple leaf shape, and turns to a clear yellow in autumn. This species
suffers frequently from chlorosis in
alkaline soils and salt burn of the leaf
margins. In spite of this the tree is useful for shade and it's graceful habit
where a large tree can be accommodated.
Leaf: Opposite, with 5 deeply palmate lobes, lobe margins serrate, 2 1/2 to 5
inches long; light green above, pale, silvery white below. Flower: Greenish or
reddish flowers appear in clusters from February to May, long before leaves.
Fruit: Appears April to June, largest of any native maple, divergent wings 1 1/2
to 2 1/2 inches long, germinate as soon as released. Twig: Similar to red maple,
often more chestnut-brown in color, unpleasant odor when crushed. Bark: Similar
to red maple, light gray when young, when older breaks up into long thin strips,
loose at ends.
Form: Trunk usually short, dividing into several subtrunks. Long slender
branches sweep downward and then curve gracefully upwards.
wood shavings used for stuffing furniture and for packing breakable objects.
Poplar trees are found throughout the Northern Hemisphere. About ten of the 35 species of poplar trees are native to North America.
Poinciana giffiesii. Bird of Paradise. A native plant, frequently shrub like in form, the bird of paradise seldom exceeds 8 to 10 feet in height. The leaves resemble those of mimosa, and the flowers are yellow with brilliant, long, deep red stamens. An extremely interesting plant, this species is grown primarily for its unusual flowers.
Prunus cerasifera. Flowering Plums. This species of the genus Prunus is highly valued for early spring bloom and highly colored foliage. While the trees are tolerant of a wide range of soil and climatic conditions, best foliage color is obtained when planted in full sun. Some corrective pruning is usually necessary on young trees to obtain a uniform, compact shape. P. cerasifera atropurpurea, the Pissard plum, is an old favorite still widely planted. Of the more recent introductions, P. cerasifera 'Krauter Vesuvius' is highly valued for profuse flowering and its deep reddish purple foliage. The 'Hollywood' variety has a more upright growth habit and light pink flowers. Other varieties of merit are 'Newport', which bears single flowers, and 'Thundercloud'.
Prunus persica. Flowering Peach. One of the first trees to bloom in the early spring, the double flowering peach is a fine species for providing color to the landscape setting. These trees are available in a wide range of colors, including red, various shades of pink, and pure white. The flowers are borne on year old wood, so annual pruning is advisable to insure adequate bloom the following year and to develop a compact well rounded tree form. The 'Flory Dwarf' is a small compact variety, about five feet high, with red, pink, or white double flowers which virtually cover the branches. The variety 'Peppermint Stick' is unique because of its variable colored flowers, often pink, white, or striped on the same branch.
Salix spp. Willows. As a group, the willows have several rather
serious faults for ornamental use. While they grow quite rapidly, the wood is
soft and weak, and numerous dead twigs usually cover the ground after high
winds; they are short lived; and they are notorious for their ability to clog
drain and sewer lines. Despite these obvious disadvantages, many people like
willows.
The weeping willow, S. babylonica, has long been a favorite because of its
graceful form and pendulous branches. Being a wide spreading tree, its use on the
home grounds is rather limited unless there is enough room for its full
development. Weeping willow is most attractive when planted along the edge of
large pools and lakes, where its branches touch the water surface.
Globe willow, S. matsudana umbraculifera, is increasing in popularity in
southern New Mexico. It is a round headed, umbrella shaped tree, growing to
about 30 feet in height.
The Navajo willow, S. matsudana 'Navajo', is a larger,
hardier form than the standard globe willow and is being planted with increasing
regularity.
Sambucus mexicana. Mexican Elder. This partially evergreen species may be grown as a large shrub or small tree. It has a crooked but well defined trunk and grows slowly to a height of about 15 to 20 feet. Mexican elder is not hardy and some winterkill of the smaller branches frequently occurs in southern New Mexico. Flat topped, yellowish white flowers are produced in profusion much of the season. Fruit set, however, is erratic and inconsistent.
Sophora japonica. Japanese Pagoda Tree. Also known as the Chinese scholar tree, this is a fast-growing, rounded, wide branching species with compound leaves resembling those of the black locust. White, pea like flowers are produced in profusion during late summer. The tree is attractive and hardy, and it tolerates a wide range of soil and climatic conditions, all of which make it useful for shade or home properties.
Ulmus carpinifolia. Smooth Leaved Elm. The 'Christine Buisman' selection of the smooth leaved elm is fast growing, ascending tree, similar in some respects to the American elm. Its chief asset is its resistance to the Dutch elm disease.
| One would think
that with Dutch elm disease, the smaller European elm bark beetle and
several other introduced pests, our elm trees have suffered enough. But now
we have yet another new beetle attacking elms in Fort Collins and other
Colorado cities.
The new beetle, which
entomologists are calling the "banded elm bark beetle," goes by the
scientific name, Scolytus schevyrewi. It's a close relative of the
smaller European elm bark beetle, Scolytus multistriatus, which is
the insect that spreads the tree killing Dutch elm disease. The banded elm
bark beetle is native to the Far East and Central Asia including China,
Mongolia, Korea, Turkmenistan, Uzbekistan, Tajikistan, Kazakhstan, southern
Kyrgyzstan and Asian Russia where it attacks a wide range of broadleaf trees
including: elms, weeping willow, Russian olive, pea shrub, apple, cherry and
plum. One of its favorite hosts is the Siberian elm, a tree that has been
widely planted in the Great Plains as a shelterbelt and windbreak species.
|
Ulmus parvifolia. Chinese Elm. Of the several elms that are known to grow in New Mexico, the Chinese is the most desirable. This species should not be confused with the Siberian elm, U pumila, widely grown in the state as the "Chinese" elm. The true Chinese elm grows to about 40 to 50 feet and may be distinguished from the Siberian by its fine textured branchlets, exfoliate trunk, and fall flowering characteristic. It is a fine all purpose yard and shade tree that should be more widely planted because it possesses none of the undesirable features of the Siberian elm.
RECOMMENDED TREES EVERGREEN
Cedrus spp. Cedars. The true cedars are among the finest, large, narrow leaved evergreen trees for southern New Mexico. Three species have been grown successfully, all of which become very large trees, 50 feet or more high with a spread at the base of 25 to 30 feet. Because of their size, their use on the average home property is rather limited. The cedars are, however, excellent choices for use in parks, school grounds, and other areas where ample room is available.
Trees of the genus Cedrus should not be confused with the native evergreen plants commonly called cedars in New Mexico. These native plants are members of the genus Juniperus.
Deodar cedar, C deodora, has been grown successfully in southern New Mexico for many years. However, it is not completely winter hardy, and injury has occurred when temperatures have dropped below zero. The foliage is silvery gray, and branch tips are pendulous. The cedar of Lebanon ' C * libani, is pyramidal somewhat like the deodar, but the branches are more horizontal. This species is slightly more winter hardy than the deodar cedar. The blue Atlas cedar, C atlantica glauca, is very similar in size and shape to the cedar of Lebanon but may be distinguished by the bluish cast of the foliage. It appears to be intermediate in hardiness to low winter temperatures.
Cupressus arizonica. Arizona Cypress. One of the most popular evergreen trees grown in the southem half of the state is the Arizona cypress. This pyramidal shaped tree grows at a moderate rate to a height of 25 to 30 feet with a spread of 10 to 15 feet at the base. The scale like leaves are gray green and remain the same throughout the year. Trees grown from seed vary considerably in form, density, and foliage color. More recently, improved varieties have been introduced which are propagated vegetatively, assuring uniformity of appearance. C. arizonica 'Gareei' is an improved variety selected for its attractive silvery, bluish green foliage. C, arizonica pyramidalis is a compact, symmetrical variety that grows to about half the size of the original species.
The Arizona cypress is a fine choice for group plantings in parks and on golf courses and school grounds, and it is also used rather extensively for windbreaks. It is native to central Arizona and southern New Mexico and does well in all but the colder northern areas of the state.
Cupressus sempervirens. Italian Cypress. This tree is a columnar cypress that grows 50 or 60 feet tall. It is widely planted in southem New Mexico. Unfortunately, it has often been used in foundation plantings of small, single story, Spanish type houses, where its height and shape tend to make the houses appear even smaller. This rapidly growing, columnar tree is best suited for use in formal gardens and around large buildings. If planted around small homes, it should be trimmed to a proportionate size. The Italian cypress is not winter hardy and can be grown only in the warmest parts of the state.
Juniperus chinensis columnaris. Chinese Column Juniper. This species is an upright, compact, narrow pyramidal juniper with blue green needle like foliage, which grows to a height of 15 to 20 feet. It is winter hardy to about 20 degrees below zero and is a fine columnar type plant for use in border and background plantings.
Juniperus chinensis torulosa. Hollywood Twisted Juniper. The twisted juniper, with its irregular, contorted, lateral branches, adds interest to any landscape setting. It is a hardy, fast growing juniper that reaches a height of about 12 feet and has a rich dark green foliage and is well adapted to New Mexico conditions. It is useful as a lawn tree for specimen planting.
Juniperus scopulorum. Western Red Cedar. This species, also known as Colorado juniper and Rocky Mountain red cedar, is native to New Mexico and grows well in all areas of the state. It will grow to 30 feet or more but is easily maintained at a smaller size by annual clipping of the branch tips. The attractive gray green foliage retains its color the year around. This is an excellent evergreen tree for lawn plantings and for windbreak use. Recent selections of merit include 'Blue Haven, 'Gray Gleam', 'Emerald Green', and 'Pathfinder'.
Juniperus virginiana. Eastern Red Cedar. The eastern red cedar, while not a native New Mexico tree, is well adapted to the state. It grows to be much larger than the western red cedar, and as it grows older its branches tend to open and the form becomes less compact. The scalelike leaves are light green during the growing season and turn a reddish brown during the cold winter months. Small, purplish berries covered with a whitish, powdery substance appear after flowering in the spring. The species is hardy and grows well in a variety of soil types. It is useful for group plantings and for windbreaks.
Recent selections include J. virginiana cupressifolia, a dense, nearly columnar form with deep green foliage, which when clipped, can be used as a substitute for Italian cypress in the colder parts of the state; J. virginiana 'Burkii', an extremely hardy pyramidal variety with steel blue foliage; and J. virginiana 'Manhattan', a compact, pyramidal variety, smaller and less hardy than 'Burkii'. Magnolia grandiflora. Southern Magnolia. This is one of the few broad leaved evergreen trees that can be grown in New Mexico. It must be considered a "marginal" tree, because its performance even in the southern part of the state has been erratic. Growth rate is very slow, chlorosis and salt burn may develop, and flowering occurs from several to many years after planting. A number of magnolias, however, are well established and have proved satisfactory. Under southern New Mexico conditions, the magnolia is much smaller than it is in its native southern areas of the United States. For best results, magnolias should be protected from strong winds and given ample room for development. The large, leathery, green leaves and the huge white flowers make the magnolia a most attractive tree. Grafted trees should be used because they are more uniform in shape and usually flower at an earlier age than seedling specimens. One of the more recent introductions, M. grandiflora 'Samuel Sommer', bearing giant sized flowers, appears to be a promising variety for southern New Mexico.
Picea engelmanni. Engelmann Spruce. This species, native to the southem Rocky Mountain areas, must be grown at the higher elevations for best results. It is somewhat slenderer than the blue spruce and retains its lower branches for a longer time. Considerable ground space is required for best results.
Picea pungens glauca. Colorado Blue Spruce. The blue spruce is also native to Colorado and to the higher elevations of New Mexico. It is an excellent evergreen tree for landscaping purposes when planted at elevations of 5000 feet or above. It
has not done well in the southern irrigated valleys of the state. The tree is pyramidal and uniformly symmetrical, but it becomes very large and requires considerable space for its uninhibited development. The foliage is very thick dense, and stiff with an attractive blue green color. Its greatest disadvantage is the tendency to lose its lower branches with increasing age
Pinus spp. Pine. Although the pines as a group are not particularly well adapted to the southern irrigated valleys of New Mexico, several species are being grown successfully at these locations. The pines thrive at the higher elevations.
For the higher elevations and northern areas R ponderosa, western yellow pine; R nigra, Austrian pine; and R edulis, pinon, the state tree of New Mexico, are well adapted for landscape use. The pinon is a smaller, slow growing species of pine and, while difficult to transplant, it is useful for the average sized home property.
In the lower elevations and southem areas of the state, P. halepensis, Aleppo pine, has been grown successfully for a number of years. It is not completely winter hardy, and severe damage will result when unusual sub zero temperatures occur. The Italian stone pine, P. pinea, has proved to be an excellent species, because it withstands wind and high temperatures and is not damaged by sub zero temperatures that injure the Aleppo pine. It is a slow growing, bushy, globe shaped tree in the early years, but it becomes somewhat umbrella shaped with age. A third species that has grown well in the warmer areas of the state is Japanese black pine, P. thunbergii. It grows very rapidly and tolerates high temperature, low humidity conditions very well. It does not, however, withstand temperatures below zero. In the formative years, the Japanese black pine is an open, straggly, irregular shaped tree and selected branches must be clipped if a more dense, uniform tree is desired.
Quercus suber. Cork Oak. While experience with this fine evergreen oak has been rather limited, performance to date indicates that it holds great promise for the southem part of the state. It has a fine textured foliage with toothed leaves, dark green above and light gray below. The trunk and main limbs develop a soft corky bark with age, adding interest to this species. Cork oak tolerates a wide range of soil conditions and appears to be well adapted to the hot, dry conditions of southern New Mexico. A useful species for lawns, streets, and parks.
Thuja orientalis 'Bakeri'. Baker's Arborvitae. One of the largest varieties of this species, Baker's arborvitae often reaches 30 feet or more in height. It is well adapted to the warm, and conditions of the Southwest and has been grown successfully for many years. While aphids and mites can be troublesome, this pyramidal shaped evergreen is a useful plant for screening or border plantings.