General Tree Care

hands in gardening gloves placing mulch

As you have probably heard, Denver is a harsh environment for trees to survive in with low precipitation, poor soil, wild temperature swings and limited urban rooting space; however, caring for trees in Denver’s unique climate is manageable and rewarding. If you follow simple steps, you can expect to see good results. From new trees to more established, this page offers general care tips including watering, mulching, trunk wrapping, pruning and more. 

Watering

Proper Watering for Newly Planted Trees

Young trees planted properly in good soil conditions and that receive adequate watering will take, at minimum, one growing season per inch of trunk diameter to become fully established. During the establishment phase, the tree will focus more on its root system and therefore will display minimal canopy growth. Follow these watering guidelines to ensure a tree becomes established:

  • First two weeks after planting: 3-5 gallons daily.
  • April-October: 10 gallons per inch in diameter, every 2-4 days, depending on weather. In periods of extreme heat, water more frequently.
  • November-March: 10 gallons per inch in diameter, every 2-4 weeks (mid-day, when the temperature is at or above 40 degrees and there is no snow cover)

Learn more about tree establishment and tree care.

Proper Watering for Established Trees

Once established, trees still need specialized care, including proper levels of watering. In April through September, water established trees weekly with 10 gallons of water per inch in diameter. In October through April, water every 2-4 weeks with 10 gallons of water per inch in diameter (mid-day, when the temperature is at or above 40 degrees). Do not water if there is still snow cover.

Other Watering Tips

You can check the moisture level of the soil to determine if more or less watering is necessary. For newly planted trees, try to find the outer edge of the root ball and dig down into the soil a few inches and squeeze the soil to feel if it is wet, dry or in-between. Wet soil will stick together and dry soil will crumble or fall apart. For older trees, follow the same process but try a few different locations between the trunk and edge of the canopy to get an average soil condition. Remember that mulch will also absorb water as you are applying, so ensure water has reached the soil before starting to count gallons applied.

Remember to increase frequency of watering during long periods of high temperatures (heat wave) and/or without precipitation (drought).

Watering frequency can also vary based on precipitation. For example, a winter with plenty of wet snow may mean little need for additional watering. However, going 3 weeks in winter without any precipitation is an indication you need to water your tree(s).

Check out this video from the Arbor Day Foundation with more tips on watering trees.

Mulch & Groundcover

Mulch can help conserve soil moisture, insulate against temperature extremes, suppress weeds and add nutrients to the soil. When adding mulch, weed barrier fabric of any kind should not be used around trees as it hinders the mulch from doing its job.

Apply wood chips, bark or other organic mulch 2 to 4 inches deep in a ring around the base of the tree out to the drip line of the branches if possible, but keep at least 6 inches away from its trunk, and replenish it every few years or as needed. Programs like Denver Recycles periodically provide wood chips free of charge. Another option is to call a tree contractor that works in your area to drop a truck of mulch or see if you can go and pick up; however, most likely it will be a mix of material and depending on circumstances, it may not be as free from debris as what you will get from the City’s recycle program. 

Soil Health

Soil health matters. It’s how trees are “fed” as they become established. The best way to enhance soil health is naturally. We recommend a process called vertical mulching for best results, as it delivers composted materials deeper into the soil, at root level. Maintaining a mulch groundcover is also beneficial, as it not only keeps water from evaporating, but also breaks down over time and naturally adds nutrients to the soil. Top-dressing with compost (underneath your mulch, in the entire planting area) is another way to enhance soil health.

We do not recommend fertilizer for young trees. Young trees, like those planted by the Be A Smart Ash program, are still in their establishment phase and focusing on root growth. Nitrogen fertilizer, the most common type of tree fertilizer, generally increases canopy growth, resulting in a decrease in root growth.

Before adding any amendments to the soil, it is best practice to perform a soil test to understand your current soil conditions and determine what improvements may be needed.

Planting & Replacing Trees

Trees on the approved street tree list are those which, given proper and consistent maintenance including supplemental irrigation, proper pruning and avoidance of chemical contaminants, are more adapted to thrive in our region and climate.

By Denver ordinance (§57-18), the adjoining property owner is responsible for all aspects of street tree care, including but not limited to planting, pruning, vegetative litter clean-up and removal.

The Denver Office of the City Forester stresses diversity when planting or replacing trees on your property and requires it in the right-of-way. The top recommended shade trees for Denver's climate include:

  • Kentucky Coffeetree
  • Chinkapin Oak
  • English Oak
  • Hackberry
  • Catalpa
  • Bur Oak
  • Sycamore
  • Texas Red Oak
  • Japanese Pagoda
  • Yellowwood

Tree Pruning & Removals

Property owners in Denver are responsible for maintaining city trees within the right-of-way adjacent to their property. There are important regulations that protect how those trees are managed.

Before pruning or removing any tree, you must determine whether it's located on private property or within the public right-of-way.(JPG, 92KB)

If you do not possess the experience or equipment to safely and properly prune or remove your tree, it’s recommended that you hire a licensed tree care professional. They use specialized equipment and have the necessary field knowledge. In Denver, tree contractors for hire are required to be licensed and insured. A list of Denver’s licensed tree contractors can be found here.

While it’s always best to use a licensed professional, if you need to prune your own trees, these tips and guidelines below share “why, what and when” pruning basics.

Why Prune?

  • Pruning helps your tree develop a strong form and structure and prevents future breakage. 
  • Removing deadwood from your tree helps prevent insect infestation and lessen risk of breakage or damage.

What to Prune? 

  • Remove dead, damaged and diseased wood (the 3 D’s).
  • Prune around stop signs and keep sidewalks clear to prevent accidents on or near your property.  
  • Branch clearance requirements are 8’ above sidewalks and 13.5’ above streets and alleys.

When to Prune?

  • Prune most trees late in the dormant season or early spring, before leaves appear, when the tree is not putting forth energy to create foliage.
  • Maples, common in Denver, should be pruned in mid- to late summer when sap slows.
  • Do not ever prune newly planted trees unless necessary. 

Tree Work Considerations

  • Tree work is dangerous, and major work often requires highly skilled individuals to complete the work safely. A professional arborist not only needs to be trained in safe tree work practices, but they also need to be well educated to understand the biology of trees.  
  • Trees are valuable and complex living organisms, and a professional arborist can protect tree health and ensure maintenance work is done safely. For the protection of people, properties and tree health, Denver’s city code establishes that it is unlawful for any person to engage in the business of cutting, trimming, pruning or removing public or private trees without a license. The Office of the City Forester is obligated to establish and monitor a list of licensed tree contractors for the City and County of Denver. 

Tree Health & Monitoring

Some trees may experience premature fall color and wilting or dropping leaves after planting because transplanting can be stressful, but it could also be a sign of pests or disease. Other signs include leaf holes and trunk wounds.

If you suspect your tree is in distress with a pest or disease, the best course of action is to contact a tree expert. You can also visit Tree Pests and Disease for more information. 

For wounded trees, do not wrap or paint the wound as this could create a warmer, moister environment that allows disease to flourish. Instead, monitor the wound and allow the tree to recover on its own. CSU Extension shares how and when to wrap trees here. 

Tree Care Supplies

Caring for trees in Denver’s unique climate is manageable and rewarding. If you follow simple steps, you can expect positive results. Trees do require some investment in tools and supplies for maintenance. Recommended tree care supplies include:

  • Water device, such as a soft spray wand and/or deep root water needle, for winter watering, but also useful year-round
  • Soil moisture meter to monitor when the soil is dry and needs water
  • A hose long enough to reach your trees if they are a long distance from your spigot
  • Tree wrap
  • Bypass blade hand pruners
  • Gloves
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