If a tree was planted properly in the best location, it should need little or no pruning. However, trees do not always grow as we imagined them to grow. Perhaps a branch is rubbing the house, or two trees grew wider than expected, and now the branches hit each other.
Pruning large trees is a safety issue, so hiring a professional is the suggested best way to handle issues like these.
When to prune trees: light pruning to remove a few small branches can be done at any time. More extensive pruning should be done in late winter/early spring, unless you have a sappy tree, like maples or fruit trees. Often it is necessary to prune trees when they are fully leafed out, so you can see where and how much to cut.
Most trees can be pruned at any time of the year. Some exceptions are American elms and crabapples which should be pruned in the winter to abate disease spread. Aspen, silver maples, birch and walnut trees exude sap if pruned in the later winter or early spring, but this will not harm the tree.
Why prune? Pruning can be thought of as cleaning – broken, dead or diseased branches, and those touching the ground, should be removed. Removing diseased branches can prevent further spread of disease. Overlapping or rubbing branches can introduce infection, so one or both should be removed. It is important to keep branches away from the sidewalk and street, where they are hazards. Weak and soft-wooded trees, like maples, should be thinned periodically to keep snow from breaking the branches and causing major damage.
How to prune: When pruning trees, be sure to use the proper tools, and be sure that they are all in good condition. Hand pruners are useful for branches less than one-half an inch thick. Loppers should be used for branches one to one-and-one-half inches in diameter. For limbs up to 20 to 30 feet high, use pole pruners or extension saws. Hand saws are popular, and can be useful for many different plants. Never remove more than one-third of a tree canopy during one season. Dead and dying wood can always be removed, but do not prune too much of the live wood.
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There are many benefits to using Colorado native trees for home and commercial landscapes. Colorado native trees are naturally adapted to their specific Colorado climate, soil, and environmental conditions. When correctly sited, they can be ideal plants for a sustainable landscape that requires reduced external inputs such as watering, fertilizing, and pruning. In order to realize these benefits, the planting site must approximate the natural environmental conditions of the plant in its native habitat.
Another benefit of using Colorado native trees in landscapes is that they attract a wide variety of wildlife including mammals, birds, and butterflies. Rapid urbanization in the state is reducing biodiversity as habitat is removed for building and road construction. Landscaping with natives on a large or small scale can maintain biodiversity that otherwise could be lost to development.
Not all native trees are available at all nurseries, so you may need to contact several commercial outlets to find a specific plant. If a tree is not sold in the trade, asking for it may help increase its availability. Native trees should not be collected from the wild because this reduces the biodiversity and causes a disturbed area that may be invaded by weeds.
There are several factors to consider when designing a native landscape. Due to Colorado’s variation of elevation and topography, native plants are found in many habitats. In order to maximize survival with minimal external inputs, trees should be selected to match the site’s life zone and the plant’s moisture, light, and soil requirements. Even if a plant is listed for a particular life zone, the aspect (north, south, east, or west facing) of the proposed site should match the moisture requirement. For example, a blue spruce, which has a high moisture requirement, should not be sited with plants of dissimilar water needs. Similarly, a blue spruce should not be planted on a south-facing slope, where a significant amount of additional moisture would be required.
Growing native trees does not exclude the use of adapted non-native plants. There are many non-native plants that are adapted to Colorado’s climate and can be used in a native landscape as long as moisture, light, and soil requirements are similar. If a site has a non-native landscape that requires additional inputs (such as an irrigated landscape on the plains), dry land native plants can be used in non-irrigated pockets within the non-native landscape. These native “pocket gardens” can be located in areas such as parkways and next to hardscapes that are difficult to irrigate.
Some communities regulate landscape appearance or the type of plants that may be used. So before completing a landscape design, check with local authorities, including homeowner’s associations, to discover any regulations that may affect your design.
Colorado can be divided into five life zones that are broadly defined by the plant communities that occur at the approximate elevations described below. The Plains life zone, 3,500 to 5,500 feet, is located in eastern Colorado where the majority of Colorado’s population resides. It is dominated by grasslands and streamside cottonwoods. In western Colorado, the Upper Sonoran life zone is located at altitudes below 7,000 feet, and in the San Luis Valley, below 8,000 feet. This zone is characterized by semi desert shrublands and piñon pine-juniper woodlands at its upper limit.
The Foothills life zone occurs from 5,500 to 8,000 feet and is dominated by dry land shrubs such as Gambel oak and mountain-mahogany, and in southern and western Colorado, piñon-juniper woodlands and sagebrush. The Montane zone consists of ponderosa pine, Douglas-fir, lodgepole pine, and aspen woodlands at elevations of 8,000 to 9,500 feet. Dense forests of Subalpine fir and Engelmann spruce dominate the Subalpine zone at 9,500 to 11,500 feet. The Alpine zone above 11,500 feet is a treeless zone made up of grasslands called tundra. Species requiring medium to high moisture occur along watercourses throughout all zones.
Successful establishment of native trees may require supplemental moisture after planting. Once established, the watering frequency can be reduced or eliminated, if the plant was sited in its native environmental conditions. Container-grown trees can be planted at any time during the growing season. Container-grown native trees are often grown in a soiless mixture of peat and bark, so the planting site should be amended with some organic material.
Using native trees offers many benefits in addition to reduced maintenance. Natives are part of our natural heritage and the ecosystems of Colorado. Native plant communities make Colorado visually distinct from the eastern, southern, or western United States. Native plant gardens are wildlife habitats and each plant contributes to the biodiversity of the state.