Trees to Avoid Planting

//Trees to Avoid Planting

Trees to Avoid Planting


“The best time to plant a tree was 20 years ago. The second best time is now.” – Chinese Proverb

We at Arborscape recommend you plant a tree as soon as possible for the many benefits they provide.  When choosing a tree, make sure to avoid the following so you don’t set yourself up for future plant health care issues and problems.

Trees To Avoid

  • Ash

  • Black Walnut

  • Russian Olive

  • Cottonwood

  • Box Elder

Ash trees are a common tree among towns and cities because of their quick growth and beautiful aesthetics. One in five urban trees are ash, making them one of the most popular trees for urban communities.

Unfortunately ash trees have problems which make them a bad choice for planting.  The first reason is that ash trees do not hold up well in storms, especially with heavy snow. This makes them expensive trees to maintain. While this is annoying the major reason we think you should reconsider planting an ash tree is because of a lethal insect called the emerald ash borer.  This is an extremely invasive pest that has traveled all the way from China and has devastated trees in the Northeast and Upper Midwest; it has now been confirmed in Boulder.

Although it has not been confirmed outside of Boulder yet, it is assumed to have inevitably spread by the time your ash tree begins to mature, making it a bad tree to plant. Mountain ash trees are an exception because they aren’t true ash trees, instead being a member of the rose family.


Trees to Avoid - image of a black walnut treeRegarding black walnut trees, we recommend avoiding them because of a new disease called thousand canker. This disease kills your tree extremely rapidly and treatments rarely stop its decline. Thousand canker is a fungal disease that has ravaged the west coast and quickly made it to Colorado.  When the fungus sets in, tiny aphid-sized beetles roam the tree and cause canker-like marks on the woody parts of the tree. Because of this disease we recommend you avoid planting black walnuts.



Russian OliveRussian Olives are currently considered a noxious species in Colorado.  The problem with Russian Olives is that the trees spread into zones along rivers and creeks.  Due to the tree’s hardy attributes, it can easily take over an area massively, killing off the native plants and changing the ecosystem for the animals as well.

There are a variety of Russian Olive alternatives that share many of their good qualities.

Russian Olive Alternatives




Cottonwood trees are not recommended for residential planting because they have weak, brittle wood and their root systems are shallow.  This makes them likely problems for one of Colorado’s many extreme weather situations.

Cottonwoods grow extremely large very fast – making tree removal and maintenance a large expense.  A great variety of insects and pests can invade this tree, as well – causing even more maintenance issues.

Cottonwoods are not drought-resistant, and will develop problems quickly without adequate water.




Box Elder are not common in the region, but they’re worth noting because they attract bugs that can invade your home!

image of Box Elder tree– found in and around homes from fall through early spring
– only a nuisance when there is a female boxelder tree in the area

– frequent exterior and interior of buildings; may stain lightly colored materials, and emit an unpleasant odor when smashed




About the Author:

Tree care updates and news items as well as best practices for canopy management to keep your trees and lawn sustainably growing. These posts represent a synthesis of our best practices and knowledge from serving thousands of customers.