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Tree Planting, Care & Watering Tips

Watering

The Colorado Front Range 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. 

Growing Season Watering Tips (April- October) 

  • Check the soil moisture at least once a week by digging down 4-inches, approximately 20” from the base of the tree. If the soil is dry, then soak well.  
  • Water approximately 10 gallons per inch of trunk diameter, two times a week. For an established or mature tree, water 15 gallons per inch of trunk diameter two times per week. Tips on tree watering in a drought pdf
  • We recommend watering slowly with a garden hose. Time how long it takes to fill a one-gallon container and multiply that time by 15 for a newly planted tree. Usually it’s around one gallon per minute.   
  • 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 three to five feet beyond the dripline on all sides of the tree. 
  • Maintaining mulch helps retain soil moisture. 
  • Avoid constantly saturated soil and begin to taper watering off during the fall.  

Winter Watering

Remember - Winter watering in Colorado is very important!  

During the winter, some root development may occur, especially for newly planted trees. Without water they may dehydrate and die before spring. Winter watering can help save your trees. 

Winter Watering Tips (October through March) 

  • Observe soil conditions to determine when water is needed. 
  • Water trees once per month when temperatures are above 40 degrees F  
  • Do not water if soil is frozen. Do not turn on your irrigation system to water your trees. 
  • Hand watering, soaker hose or drip applications are best  
  • 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. 

Evergreen Trees

  • Evergreen trees (pine, fir and spruce) are at higher risk from drying winter conditions because they retain their needles (which can lose water all winter). 
  • Winter drying/damage is typically more severe when trees are in sunny, dry, wind-exposed areas 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. 

Deciduous Trees

  • 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. 
  • A lack of water may also stress your tree and make it more vulnerable to attack from insect and disease pests.  

Mulch

Maintain wood mulch around the base of the tree throughout its lifetime to increase growth and optimize tree benefits. Mulch plays an important role in regulating soil temperature, maintaining soil moisture, and serves as a barrier to potential damage from string trimmers and mowers.  

Mulch Tips 

  • Use wood chip or bark mulch 
  • Keep a 2 to 4-inch depth of mulch around the tree. 
  • Extend mulch layer out to dripline of young trees. 
  • Be sure not to pile mulch up around the trunk of the tree, pulling back 1’’ from trunk 
  • Do not place sod or plant grass at the base of your tree. Turf grass competes with the tree for water and nutrients. 

Mulch is available free to Boulder residents from Western Disposal. You will see the sign for the city mulch pile when driving east on Pearl Parkway between 49th and 55th St. 

Stakes

We may have staked your public street tree when it was planted.  

Some trees need staking to provide stability for the roots. If your new public street tree was staked, we will remove the stakes after one year. 

Support stakes can do more harm than good when left too long. Stakes restrict movement which reduces natural growth processes and causes the tree to be less able to bend with the wind. 

Tree Wrap

Wrap your tree seasonally to prevent sunscald. Most young, thin barked trees are susceptible to sunscald. Sunscald occurs in winter months during a warm day when temperatures may be high enough to activate cells and tissues beneath the bark. These activated cells freeze at night or when temperatures drop. The frozen cells shrink and die, leaving elongated, sunken sections of dead or cracked bark.  

After few years, tree wrap is not necessary in the winter months. As trees mature, their bark will thicken, providing natural insulation and protection to underlying tissues.  

Tree Wrap Tips 

  • Wrap your trees with commercially available tree wrap.  
  • Start from the bottom and wind your way up the tree, securing with masking tape.  
  • Wrap your trees from October through April for at least the first two years after planting.  
  • Do not leave wrap on your tree year-round as this can make your tree susceptible to insects and disease.  

Pruning

We provide street tree pruning on a rotational basis for publicly owned trees. Residents are not permitted to prune publicly owned trees. However, if you would like to hire a Licensed Certified Arborist to prune a public tree at your own expense or feel that your street tree requires pruning to mitigate low hanging branches or poses a safety concern, please fill out a request. 

 

Landscaping around Street Trees

Keep the mowers and weed whips away! 

Before beginning work on your property, consider the possible impacts to trees in the public Right of Way or on your own property. 

Most tree roots are in the top 6"- 18" of the soil and extend out beyond the canopy (dripline). Construction and landscape installation within the root zone can seriously damage your trees. Trees that suffer severe root damage may not show symptoms for several years. The damage is not reversable, but it is preventable.  

In addition, damage to the bark and the underlying tissues can seriously injure the tree. It is important to be aware of how your landscape practices can help or harm trees.  

Tree Protection Tips

  • Avoid attaching any objects to your tree.  
  • Avoid placing sod or plant grass near the trunk of your tree. Grass out-competes the tree for water and nutrients and requires trimming, which increases the likelihood of bark and root damage from mowers and weed whips.  
  • Do not use a rototiller within the tree dripline. If it is necessary to scarify soil, do not penetrate deeper than 4". 
  • A well-maintained mulch ring around your tree will protect the trunk from mechanical damage and retain soil moisture. 
  • Avoid grade changes in the root zone. Removing even a few inches of soil can seriously damage roots. Adding just a few inches of soil can decrease 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. 

Contact Boulder Forestry before doing any major landscape projects including irrigation installation within the root zone of any public street right-of-way trees.