Using This Guide
This tree selection guide is divided into broadleaved trees, most of which are deciduous, and coniferous trees, most of which are evergreen. The characteristics in the table generally are for the species or most commonly planted cultivar, though some species show a wide range in characteristics between cultivars. Cultural characteristics, mostly involved with site selection and planting, along with some comments and limitations, are shown on the left. General species characteristics and ornamental features are shown on the right, along with some common cultivars. A detailed description of table information and symbols follows:
- Species are listed alphabetically by Latin name in italics, followed by common name(s).
- in front of the name indicates a tree native to Utah.
- t) indicates a tree that rarely should be planted, though limited use in specific situations may be justified.
- Tolerance of poor drainage (flooded or compacted soils with low oxygen availability), drought (lack of water), alkalinity (high soil pH; higher than 6.5 to 7), salt (mainly referring to salt spray or deposition on tops, though this may indicate some tolerance to soil salinity), and shade (lack of sunlight) is indicated by the letters L(ow), M(edium), or H(igh).
- Ease of transplanting also is indicated as L(ow), M(edium), or H(igh). Low ease of transplanting indicates plants that must be especially well-cared for during and after the transplanting process. Such trees often do better when their size at transplanting is small.
- USDA plant hardiness zones are given to indicate a plant's cold-hardiness, but also give some indication of heat tolerance. The contiguous United States and southern Canada have been divided by the USDA into eleven zones that correspond to a 10°F range in average annual minimum temperatures (see map on page 11). Annual average minimum temperatures for each zone are as follows:
Zone 1 - below -50°F Zone 5 - -20 to -10°F Zone 9 - 20 to 30°F
Zone 2 - -50 to -40°F Zone 6 - -10 to 0°F Zone 10 - 30 to 40°F
Zone 3 - -40 to -30°F Zone 7 - 0 to 10°F Zone 11 - 40°F and above
Utah's hardiness zones range from zone 3 in eastern Rich County, to zones 5 and 6 in the Salt Lake City area and most of the rest of the state at lower elevations, to zone 7 in southern Utah and even zone 8 in the Glen Canyon and St. George areas. Species should only be planted beyond their recommended zones on a trial basis.
■ Comments and limitations are referred to by number and are defined as:
1 - May be insect and/or disease prone, especially when stressed.
2 - Weak wood and/or branch structure.
3 - Fruit and/or plant parts can be nuisances; use fruitless varieties if possible.
4 - Thorns or spines that can be dangerous; use thornless varieties if possible.
5 - Sucker (sprout) growth can be a problem.
6 - Prefers abundant water, but some of these species may survive on a drier site.
7 - Evergreen broadleaf (retains its leaves for more than one year).
8 - Deciduous conifer (loses its needles every year).
- Growth rate refers to height growth for the first ten years after a tree is planted and is shown as follows: Low - <12 inches/year; Medium - 12-24 inches/year; High - >24 inches/year.
- Mature height will vary considerably by cultivar and site and is shown here for the species assuming adequate care: Low - <20 feet; Medium - 20-40 feet; High - >40 feet.
- Longevity refers to the average life span of a tree and may be much shorter on harsh sites or where the species is poorly adapted. Longevity is shown as: Low -<25 years; Medium - 25-50 years; High - >50 years.
- Trees that are suitable for planting under or near most powerlines are indicated by a check (✓) in that column. This means that their mature height is under about 25 feet. A star (•) in the power line column indicates that certain, usually dwarf, cultivars are suitable under powerlines, while others are not. Be careful to check cultivar heights when buying. If in doubt, contact your Extension Agent or your electricity provider.
- Crown shape varies considerably by cultivar and sometimes by site. The common crown shape for a species is shown as follows: Broad, Columnar, Irregular, Layered, Oval, Pyramidal, Round, Shrubby, Vase, Weeping.
- The availability of cultivars for a species is indicated in the last column. A few noteworthy cultivars are listed for each species where available, with a note about the cultivar's distinguishing characteristic(s). Some common cultivar names and their meanings are:
- Aurea' or 'Aureum' - golden or yellow leaves during the growing season 'Columnaris' or 'Columnare' - very tight, columnar crown 'Compactum' or 'Nana' - dwarf or small-crowned 'Fastigiata' - narrow crown form
- Glauca' - foliage with a whitish or silvery cast, usually due to a white waxy coating
- Globosa' or 'Globosum' - globe-shaped crown 'Laciniata' or 'Laciniatum' - "cut" or deeply lobed leaves 'Pendula' or 'Pendulum' - pendulous branches or weeping crown shape 'Purpurea', 'Atropurpurea', or 'Atropurpureum' - purple leaves in growing season
- Umbraculifera' - umbrella-shaped crown 'Variegata' - variegated leaves showing multiple colors
Keep in mind that this is only a partial listing, and cultivars often exist with much different characteristics from the original species. Even where named cultivars don't exist, it is important to know the seed source or seed collection location for the tree you are planting. Choose species or seed sources from locations as similar as possible to your planting site. A few of the species listed here would not be found at all outside of extreme southern Utah.
Finally, remember that cultivars can be interesting and unique, but don't ignore the value of the original species. For example, typical native trees of the species American linden (Tilia americana) in many ways are better than any of the cultivars that have been selected.
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