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Seasonal Tree Care

Spring/Summer

is a great time of the year to plant trees. It is less stressful on the tree to plant before the dry, hot temperatures begin.

  • Wood chips (mulch) should be placed around the base of trees to keep in moisture, discourage weeds and prevent mowing equipment from damaging the bark.
  • Most trees are subject to windy conditions and should be staked at the time of planting if they are 1" diameter or larger. Stakes should be removed after one year if the tree is planted in the spring. If the tree is planted in the fall, leave the stakes on longer for the windy season to subside and remove the following spring. Stakes that are left on much longer than one year interfere with proper development.
  • Supplemental water will be required, especially during the summer months but avoid constant saturated soil conditions.
  • Tree wrap placed on newly planted trees last fall should be removed by late March or early April. Wrap that is left on during the summer months can lead to serious insect and disease problems.

Help out your street trees! Many trees growing in the right-of-way strips do not have a water source. A cooperative effort exists between the City and the adjacent property owners in caring for these trees. We ask that residents help water trees throughout the growing season. Check soil moisture every week by digging 4"-6" deep about 24" from the tree trunk. Water if the soil is dry.

Spring and summer is often when people consider changing or improving their landscaping. Before beginning work, consider the possible impacts to your trees.

  • Most tree roots are in the top 6"-18" of the soil and extend out beyond the canopy (dripline). Construction within the root zone can seriously damage your trees. Trees that suffer severe root damage may not show symptoms for several years.
  • Avoid grade changes in the root zone. Adding or removing just a few inches of soil can make a big difference in the amount of oxygen, water and minerals available to the roots.
  • Parking vehicles or stockpiling materials under trees can crush roots and cause soil compaction which limits the water and oxygen available to roots.
  • Protect tree roots when installing sod. Try to avoid using a rototiller within the dripline. If it is absolutely necessary, don’t penetrate deeper than 4".
  • When installing an irrigation system plan it out carefully to avoid cutting large roots. Hand dig if possible within the dripline and place lines under the large roots. If a tree root needs to be cut, use a pruning saw to make a clean cut. A good cut will close over faster.

Contact the Forestry Division before doing any major landscape projects within the root zone of City street right-of-way trees. 


Fall/Winter

Most homeowners realize the need for watering during the growing season, however many may not realize the need to water when their trees and shrubs are dormant. During this time, some root development may occur, especially for newly planted trees and shrubs. Without water they may dehydrate and die before spring. Winter watering can help save your trees. Even though trees are dormant during the winter, their root systems need moisture to remain alive. Since winter temperatures in Colorado fluctuate greatly, it is best to closely observe soil conditions to determine when watering is needed. For extended warm, dry winters even established trees need supplemental watering.

Periods of drought are common on Colorado's Front Range but even in years when drought is not a concern winter watering is crucial! This area is naturally a semi-arid, shortgrass prairie that would have few trees without irrigation. Growing trees here is difficult in wet years, not to mention the challenges in drought years. Properly placed and maintained trees are an asset to the environment and to our community.

Evergreen trees are more at risk from drying winter conditions and need more water to survive because they retain their needles and can lose water all winter long. Winter winds can compound the problem by pulling water from the needles. Winter damage is typically more severe when trees are located on hot, dry exposures such as the south or west sides of structures. Symptoms from lack of winter watering can appear immediately and will include browning of needles. The entire tree may be affected.

Even though deciduous trees appear dormant during the winter, their root systems continue to slowly grow and need moisture to survive. Water is lost through twigs and must be replaced to prevent damage. Deciduous trees most at risk from drying winter conditions are shallow-rooted species such as maples, lindens, birches and any recently planted tree. Damage from lack of winter watering won’t show up until the following spring and could include branch dieback, reduced leaf size, chlorosis (yellowing of leaves) or tree mortality.

Some winter watering tips:

  • Water your deciduous and evergreen trees up to two times a month between October and March.
  • Check soil moisture levels around the dripline of the tree to determine how much water is needed. To accurately determine soil moisture, dig down at least 4-6 inches.
  • Water during the day when temperatures are above 40 degrees to allow the water to soak in before freezing night temperatures. Do not water if soil is frozen. Hand watering, soaker hose or drip applications are allowed up to two hours per area with no day or time restrictions.
  • Soaker hoses, soil needles or hoses with a soft spray attachment can be used to water trees in the winter. Do not turn on your irrigation system to water your trees.
  • How much water your tree should receive depends upon the tree size. A general rule of thumb is to use approximately 10 gallons of water per inch of trunk diameter for each watering. Measure trunk diameter at knee height. General formula: Tree Diameter x 5 min. = Total Watering Time
  • The most important area to water for deciduous trees is within the dripline (from the trunk to the outer edges of the trees branches). For evergreens, water 3-5 feet beyond the dripline on all sides of the tree.
  • Maintain mulch 4 inches deep around trees and shrubs to retain moisture. Pull mulch back from the tree trunk. Mulch is available free to Boulder residents from Western Disposal.

Well-timed fall and winter watering may allow a tree to survive on less water than a regime of plentiful water applications during the growing season.

Adopt a tree!
Water a tree in the median or right-of-way that may not be receiving water.


Authorization is needed from the City Forester before planting, pruning, spraying or removing any tree in the city right-of-way. This enables the Forestry Section to keep an up-to-date tree inventory and ensures proper species selection, placement and care of new or existing trees. For more information, call the Forestry office at (303) 441-4406, Monday-Friday, 7 a.m. - 3:30 p.m.

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