Frequently Asked Questions
and Helpful Tips

We offer natural form pruning, tree removal, and plant health care.

Mark Mortensen will be present on each job, accompanied by another ISA Certified Arborist and ground crew.

Yes, we have all necessary licenses for our area, and we carry insurance for all of our projects.

Centennial – Littleton – Englewood – Greenwood Village – Highlands Ranch – Lone Tree – Bow Mar – Lakewood – Aurora – Denver – Wheat Ridge

Many folks are well aware that a very aggressive insect pest called the Emerald Ash Borer (EAB) was detected in Boulder, CO in September 2013. EAB is an outright killer of ash trees and there are efforts under way to slow or confine the attack. It is now thought that EAB has actually been in Boulder for six years before it was detected.

There are efforts being made to confine EAB but it may already be present in other parts of Colorado that we are unaware of. The fastest way to speed the spread and distribution of EAB will be by movement of infected firewood. There are quarantines in place and fairly well-publicized campaigns about moving firewood or wood debris.

There are other boring insects that also attack ash trees including the lilac ash borer, ash bark beetle, and the flatheaded apple tree borer. These insects are considered native insects, and though they cause significant damage to ash trees, the trees can usually survive, but ash trees infested with EAB will likely die within three – six years after attack.

Most options to prevent borer problems using insecticides are expensive, and most are also not really healthy options for the soil and will kill beneficial insects (like honey bees), microorganisms, earthworms, nematodes, and beneficial bacteria in the soil. This is why The Colorado Department of Agriculture, CSU and others who have been studying this are cautioning about using such remedies or preventions until the pest is within 5 miles. However, the chemical suppliers are urging using their pesticides as a preventative and often cite Nebraska’s suggested distance of 15 miles, and also, we may not know of every location where EAB is present.

Mortensen Tree Service has its own beliefs and suggested strategies for protecting trees from insects and disease that are based on science, commonly published facts by the International Society of Arboriculture, the Colorado Tree Coalition, major universities, and supported by years of personal observations of all types of landscape issues.

The underlying thread of all insect disease problems is stress. Stressed trees are most vulnerable. How do we prevent stress in trees? We create healthy soils that allow for healthy roots that support heathy top growth in all types of plants – trees, turf, flowers, vegetables…

Mortensen Tree is the manufacturer’s representative for EnviroTree which is made from all food grade ingredients. When used as directed it can be used as a stand-alone product eliminating the need for other toxic and poisonous products on your lawn and trees. It is environmentally safe, has no hazardous components. EnviroTree is a different science than that which is embraced by the chemical companies and those companies which spray or inject such dangerous and poisonous chemicals. EnviroTree is easy and safe for a homeowner to use. It is very cost effective and will get the desired results.

A common request is to thin a tree out excessively with the anticipated outcome of allowing snow to pass through the branches minimizing the chance of broken limbs from spring or fall snowstorms when the deciduous trees are in leaf. Another common concern is that the tree branches will touch or rest on the roof as a result of snow loading.

If this request is fulfilled and the tree is excessively thinned, the tree may actually become more vulnerable to storm damage. Let me explain why a denser tree can better survive and “weather the storm” without storm damage or limb failure.

In the Denver area, it is not unusual to have early fall or spring snow storms when the trees are leafed out. And often, I hear the comment, “I don’t understand why this happened, we just had the trees trimmed!” My explanation is simple; the trees were excessively trimmed, setting them up to failure.

The snow generally is loading from the top down. A properly pruned tree will have an even distribution of branching throughout its structure. As the topmost branches become weighted by the snow, they come to rest and are supported by the next set of branches. Typically, the branches will be stronger and greater in diameter as you go down. As the storm progresses, these branches may also become snowloaded and begin sagging. If there is another set of branches for support, or as things progress with this snow loading process and the branches eventually rest on the roof, all is fine. After the storm clears and that “big heater in the sky” comes out, the snow melts or falls off the branches, they spring back up, and all is well.

If the tree has been excessively thinned or raised too high off the roof, this network of supporting branches is gone. Then, as the weight increases, the branch eventually reaches its threshold and breaks.

(In some parts of the country, it is valid to raise the branches more than I would here in Denver because of humidity issues. With our dry climate I don’t consider it as a factor. For roof clearance, I look for adequate clearance so branches aren’t banging or hitting the roof even on windy days but will be able to be supported by the roof during a snow loading event.)

I have been consistent during my twenty-year career as an arborist keeping the trees relatively safe from storm damage and almost never get calls for “Emergency Tree Service” from my clients. My adhering to this theory and approach to pruning the trees has kept them strong and able to survive the storms. The calls for emergency service are generally from “new” people looking for help.

Sometimes it is possible to knock the snow off of some of the lower branches with a pole. A broom can work well on shrubs and smaller trees. Be gentle, damage may occur to the bark, or you may even break branches accidentally. Remember, this can be dangerous. Always wear a hard hat and eye protection when working with trees, even knocking snow off the branches.

Most plant problems can be attributed to an inferior or lacking root system.
Whether we are looking at trees or turf, most plant problems can be attributed to the soil which is not allowing sufficient root development to support the top health of the plant. Most insect and disease problems are the result of environmental stress. If we can improve the growing conditions in their environment, they are less susceptible to insects and disease. That is what we do at Mortensen Tree Service; we evaluate the soil to get at the root of the problem.

Mortensen Tree is on the cutting edge of science and plant health care. We are tirelessly promoting EnviroTree, Ultimate Turf, and other products produced by Solutions4Earth. These products are mostly food grade ingredients and are much more environmentally friendly than traditional synthetic programs.

Our biggest challenges in Colorado are soil health and adequate moisture. If we can promote a healthy soil, we can then produce roots to support healthy trees, plants, and turf in our landscapes.

Mortensen Tree is the distributor for Solutions4Earth, and you can purchase the products from us or have us apply them for you. I invite you to visit

Shake the product well. I have found it easiest to set the jug on its side and rock it back and forth to be easiest for me.

Trees – Use full strength, apply from about three or four feet high to the ground directly on the bark. (Bark only full strength). Spray accurately avoiding contact with foliage. If applied near foliage like flowers planted around a tree, wet area first, apply EnviroTree, and then rinse foliage. Full strength applications are for bark only.

I generally use a Gilmour 2 quart pump sprayer. Look for one that has a wide mouth to make filling easy.

Lawns – Using an Ortho Dial-n-Spray sprayer set on 6 or 8, apply at least one quart per 1,000 square feet on good lawns. Correcting troubled lawns or first-time applications, I apply a gallon or more per 1,000 square feet. Repeat four to six times a year during growing season.

Water helps move the product thru the soil. Additional watering or rainfall is beneficial to the application.

I do “hot-rod” the Ortho sprayer by removing the screen on the end of the intake tube. This allows any of the larger particles to easily pass thru. On lawns, I generally go with 6 ounces per gallon rate on turf.

Flowers and shrubs – Use the Ortho Dial-n-Spray set at 1 or 2 ounces per gallon rate. Spray both the plants and the soil. Better yet, have ET to bottom of label on Ortho sprayer add water to top diluting in sprayer and continue spraying at 6.

Helpful Links

ISA Rocky Mountain Chapter
Colorado Tree Coalition

International Society of Arboriculture
Solutions 4Earth

Tree Care Industry Association
Trees Are Good