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Colorado State Forest Service News

Fall is ideal time to plant trees

two people plant a tree in a front yard in the fall.
Fall is an excellent time to plant trees in Colorado. Photo: Ryan Lockwood, CSFS
Find the perfect tree for your property with these tree-buying tips.

A great time to plant trees in Colorado is in the early fall, September 1 – October 15. This is the sweet spot, when the ground is still warm enough to dig holes and the newly planted trees will have time to start growing roots before cold temperatures arrive. The trees require less care during the dormant winter months, increasing the chances of survival. (If you can’t get to it right now, another great time to plant trees is in the spring, from March 15 to June 15.)

Before you go to the nursery to pick your new trees, it’s crucial to do a little homework and identify trees recommended for your yard. The Colorado State Forest Service and Colorado Tree Coalition have resources to help you narrow down the perfect new tree (or trees!) for your property. When developing your list of ideal trees, evaluate how much sun the chosen tree spot gets, and create a plan for watering regularly.

But you may feel overwhelmed in a nursery, standing among the trees available for purchase. How do you pick out a healthy, viable tree? Our urban and community foresters are here to help. Next time you go tree-shopping, follow this advice and feel confident in your choices.

Tree-buying tips

Picking a good tree comes down to structure, health and roots. Take a top-down approach: Start at the top of the tree and evaluate the branches and make your way down to the root ball.

Good structure

  • Look for a strong leader – usually a single main branch that points up. Avoid trees that have two or more leaders, branches of similar diameter that grow up from roughly the same place. Also called codominant stems, these may compete with each other, leading to structural weakness.
  • Inspect the tree from all sides to make sure branches go out in all directions, not just two or three sides.
  • Look for branches that grow out in more of a U-shaped joint rather than a V. A wider angle coming off the main stem is ideal because a narrow angle may result in a poor form as the tree grows, resulting in branch failure from strong winds or heavy snow.

Another reason to avoid a V-shaped joint is that they often indicate “included bark,” which creates a weak branch connection.

Overall health

Plants in poor health attract pests and require more maintenance, so it’s important to choose a strong, robust tree.

  • Look for a vigorous plant with good shoot growth and healthy foliage.
  • Make sure branches DO NOT overlap or rub each other.
  • Avoid trees that show signs of insects or disease such as defoliated leaves, leaf spot or blotches, or discoloration or ooze from an old wound.
  • Avoid trees with damage to branches and the main stem of the tree.
  • Avoid trees that have suckers (extra growth) coming up from the roots or lower trunk.
diagram of issues to avoid when choosing a tree.
This illustration shows common issues to avoid when purchasing a tree. Illustration credit: International Society of Arboriculture, Bugwood.org

 Root inspection

  • First, go ahead and remove the plastic pot and inspect the roots while you’re at the nursery!
  • Inspect the root ball for any girdling roots; these are roots that grow in a circular pattern around the trunk. These roots can limit the tree’s ability to establish a solid root system beyond the root ball, as they tend to continue growing in that pattern. So look for a tree with minimal girdling roots, and if they’re present, take care to address them before planting.

Taking a little time to prepare for your trip to the nursery will help you find the perfect tree for your property. Trees are an excellent investment, and choosing healthy, strong seedlings will increase the chances of your new trees flourishing for years to come. Next step: Correctly plant your new tree by following this step-by-step guide.   

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