Tree Care

We recommend trunk wrapping for young trees—as long as you follow the wrapping guidelines! Sadly, improper wrapping is a common cause of young tree death. That’s because young trees are susceptible to sunscald and frost cracks due to drastic winter temperature fluctuations. To prevent bark damage, be sure to wrap the trunks of younger trees up to the first branches using commercial, brown paper tree wrap, available at home improvement stores or online (don’t use plastic or fabric!). A general rule of thumb is to wrap the trees around Thanksgiving and remove the tree wrap around Easter. Just don’t forget to remove the tree wrap in the spring! New trees should be wrapped for their first three winters after installation.

CSU Extension shows you how to properly wrap a tree for the winter. 

Yes. Applying mulch is the best way to protect your tree and give it the nutrients that it requires. Apply wood chips, bark or other organic mulch 2 to 4 inches deep in a ring around the base of the tree, but at least 3 inches away from its trunk. Mulch reduces soil evaporation, improves water absorption, insulates against temperature extremes and can break down over time, adding necessary nutrients to the soil. Make sure to replenish your mulch at least a few times a year. Avoid other types of mulch, especially rocks, as they can interfere with healthy tree establishment and growth. Some recycling programs like Denver Recycles provide wood chips free of charge. 

Generally, no. Staking can cause weaker trunks and less–developed root systems. We only recommend staking if your tree will not stand straight on its own, because it’s in a high wind area or was planted in extremely loose soil. Use wide, flat straps to attach trees to stakes. Don’t use wire, string, rope or rubber hose around a tree. These structures can girdle, or “strangle” a growing tree, prohibiting the tree from transporting the water and nutrients it needs, eventually causing tree death. Remove stakes and straps after roots are established, usually after one or two growing seasons. Learn about staking trees from the University of Minnesota and planting and caring for trees from CSU. You can buy all necessary staking material at your local nursery or hardware store.  

Important things to remember when staking: 

1. Use soft materials against the bark of the tree to protect it during this time. No twist-ties, wires, zip-ties or thin string that can cause cuts and abrasions to the bark. 
2. Allow your tree to have some sway, so don’t stake it too tight. This can help it grow the proper array of stabilizing roots to remain sturdy for the rest of its life. 
3. Make sure the staking helps the tree stand straight. It doesn’t help if you stake the tree in the wrong direction, pulled to one side. 
4. Do not leave the staking material on for more than two years as this can cause the tree to rely on staking to remain stable.  

During the first three years, prune ONLY dead, damaged, or diseased branches. You can also remove suckers (shoots that grow at the base of the tree) and branches that cross and rub one another to ensure proper vertical growth. Many species in Denver have specific pruning constraints. Check out this Be A Smart Ash resource for more tips on pruning.

Reach out to Denver Forestry prior to pruning for questions, concerns, or more information at tree@denvergov.org or forestry@denvergov.org.  

During establishment, the tree will focus more on its root system and have minimal canopy growth. With correct planting technique, good soil conditions, and proper watering, tree establishment takes one growing season per inch of trunk diameter. We typically plant 1.5-2-inch caliper trees, so establishment will likely take 2-3 years under ideal conditions. Tree establishment may take longer with improper planting techniques, improper tree maintenance, and/or poor soil conditions.  

For more information on tree establishment and tree care during the establishment phase, review https://cmg.extension.colostate.edu/Gardennotes/635.pdf. 

Our planting contractor will water the tree after planting. Follow these general instructions for newly planted trees for the first two years after planting: 

*Do NOT water wet soil 

**Mid-day, when the temperature is at least 40 degrees 

Other watering tips: 

• Allow soil to dry between waterings 
• Be sure to check soil moisture to determine if more or less watering is necessary 
• Increase frequency of watering during extended periods of high temperatures (heat wave) and/or without precipitation (drought) 
• In preparation for winter, perform a deep root irrigation: Water your tree with 15 gallons of water with a slow trickle over several hours 

We recommend following our watering guidelines for at least two years after the tree installation to ensure that your tree becomes established. This is because your tree needs extra water while it grows back roots cut off during transplanting. After your tree becomes established, you can reduce the watering frequency. However, we still recommend following the 10 gallons of water per inch caliper of the tree, watering when we experience long periods without precipitation and throughout the winter. You can continue to monitor your soil moisture to determine when your tree needs to be watered. 

A good way to check is by feeling with your hand. Dig down into the soil a few inches and squeeze the soil with your hand to feel if it is wet, dry, or in between. Wet soil will stick together, dry soil will crumble or fall apart. You can also invest in a soil moisture meter – this low-cost device allows you to probe the soil and determine the moisture content.  

A simple hose is the most basic tool needed to water your tree, but soaker hoses, soft spray nozzles and soil needles can help break through the soil surface. Most absorbing tree roots are found in the first 12-inches of soil depth; apply water slowly, so it has time to absorb into the soil and reach these vital roots.  Monitor your watering and if the water is running off and not soaking in, reduce the rate of your watering.  

In the fall and winter, trees drop their leaves and become dormant as they prepare for colder temperatures. However, roots never go dormant and still need water to survive. Colorado often experiences dry periods over winter (2 or more weeks without precipitation), which can leave roots susceptible to drying out, causing tree death or severe root damage. Do not water when temperatures are near or below freezing, as this can also cause root damage. See Q1: My tree was just planted. Do I need to water? Watering Guidelines for more information on how to water your tree in the winter. 

You can determine your hose’s output by taking a container of known quantity, like a gallon jug or five-gallon bucket, and setting a timer for how long it takes the hose to fill up the container. Then you can calculate how long you should trickle your hose to achieve a certain quantity of watering.  

For example, if it takes a hose 2 minutes to fill up a gallon of water at a trickle and you need to give your  tree 15 gallons of water, then you should water for 30 minutes at a trickle. Be sure to move the hose around the base of the tree to evenly water all roots. 

There are some conversions to measure how much output a sprinkler system has, but most of these are measured in inches. For trees, an irrigation system is helpful but is generally not enough water to get the tree established. We recommend using a ‘tree gator’ watering bag and/or a watering hose, in addition to an irrigation system.

Please review https://cmg.extension.colostate.edu/Gardennotes/657.pdf for more information on ways to water trees.  

Buckets or a ‘tree gator’ watering bag can be used in these cases. You want to make sure the water is delivered slowly if you are using a bucket, so do not dump the water. Click HERE for a great way on how to convert 5-gallon buckets for better tree watering. You can also use your garden hose – just remember to disconnect your hose from your outdoor spigot.  

Most likely, yes. We generally get very little precipitation in Denver, and when we do, it can be short and heavy. This type of rainfall usually does not fully absorb into the soil, especially in many areas of Denver that have heavy and compacted soils. If you are unsure, check the soil moisture prior to watering. See: Q3: How can I check if my tree needs to be watered? above for more information.

Vertical Mulching: Vertical mulching is a technique used to help alleviate soil compaction in the critical root zones of trees. It is also effective to improve soil conditions after construction projects.  Compacted soil can be detrimental to a tree’s health by reducing the movement of water and oxygen throughout the soil– both vital to the tree’s wellbeing.  Vertical mulching involves removing columns of poor-quality soil around the tree in a radial or grid pattern. Holes are then filled with compost. Vertical mulching provides many benefits, including providing necessary nutrients, soil aeration, and allowing deeper water penetration. Please watch this video for more information.  

Nitrogen fertilizer generally increases canopy growth, resulting in a decrease in root growth. Because the trees we plant are young and still in their establishment phase focusing on root growth, fertilizer is not recommended. If soil conditions are poor, then see Q1: How to improve soil conditions through vertical mulching. One of best ways to help your tree is to continue to replenish the organic mulch layer around your tree.  

For more information on fertilizing shade trees, review https://cmg.extension.colostate.edu/Gardennotes/635.pdf. 

No. Rocks used as a ground cover are detrimental to trees and shrubs. Rocks retain heat, which in turn raises the soil temperature and increases evaporation; this leads to stressed, thirsty plants that require even more water. Rocks also will not provide any essential nutrients and can change the soil chemistry which can be unfavorable for many trees. While rocks and xeriscape lawns can be a way to conserve water in other areas of your garden, it is essential that the area with your tree roots is covered with mulch or other organic material.  

Grass around the base of the trunk is not recommended. Grass competes with young trees for moisture and nutrients in our already water–scarce climate. Additionally, having grass close to your tree increases the risk of mechanical damage to the trunk from lawn mowers or string trimmers. Maintaining a ring of mulch around the base of the tree is the best groundcover in our urban setting.  

Grass around the base of the trunk is not recommended. Grass competes with young trees for moisture and nutrients in our already water–scarce climate. Additionally, having grass close to your tree increases the risk of mechanical damage to the trunk from lawn mowers or string trimmers. Maintaining a ring of mulch around the base of the tree is the best groundcover in our urban setting.  

Your tree will likely require more water than our guidelines because of the surrounding pavement/metal. Pavement and metal retain more heat, which raises the temperature, increasing evaporation. It’s important to check the soil moisture to determine when your tree needs water in these types of planting locations.  

Particularly wet and heavy snow can catch on the branches of young trees, causing them to bend and sometimes break. When this type of snow occurs, gently shake the branches of the tree as soon as possible to relieve the weight and prevent damage. If a branch is broken, prune the branch to create a clean cut.  

You can easily check to see if a young tree is alive by a flexibility or bark scratch test. Branches that are alive should be pliable and bendable. If they snap when you bend them, they are dead. Check as many branches as possible in the crown of the tree to see how many are alive. You can also perform a bark scratch test using your fingernail or knife: GENTLY scratch off a tiny section of the outer portion of bark – it should reveal green underneath. If there is no green, then that branch or trunk is likely dead. 

Most likely, no. It’s not uncommon for some trees to experience this after planting. Transplantation can be a stressful event for trees and some will drop their leaves to focus their energy elsewhere, like in growing their root system. Please continue to water your tree even if the leaves drop. You can determine if the tree is still alive using the methods in Q1: I think my tree is dead. How can I tell? 

The suckers growing from the base are a sign of stress, most likely from the tree not getting enough water. If the trunk and crown of the tree are still alive, prune back the suckers and make sure your tree is getting enough water. See Section 1: Watering, Q1: My tree was just planted. Do I need to water?  above to ensure that your tree is getting adequate water.

The suckers growing from the base are a sign of stress, most likely from the tree not getting enough water. If the trunk and crown of the tree are still alive, prune back the suckers and make sure your tree is getting enough water. See Section 1: Watering, Q1: My tree was just planted. Do I need to water?  above to ensure that your tree is getting adequate water.

We have a number of insects on the front range that like to nibble on leaves. For healthy trees, this is likely not a cause for concern and is a sign of an ecosystem at work. CSU Extension provides information on many of our most common pests. Learn more about the  Japanese Beetle and Elm leaf beetle.  

Healthy trees should have the ability to compartmentalize most wounds, as long as they aren’t too severe. Do not wrap or paint the wound as this could create a warmer, moister environment for diseases.  Monitor the wound and allow the tree to recover on its own.