Quick answer: Good replacements for ash in Denver include hackberry, disease-resistant elm, Kentucky coffeetree, oak and catalpa. Those are the species Denver’s own free street tree program commonly plants. Do not replace an ash with another ash: the city’s Be A Smart Ash program says further planting of ash in Colorado is not recommended.
With emerald ash borer now in Denver, many ash trees will come down over the next few years. This guide covers what to plant in their place. For the removal itself, see ash tree removal in Denver.
Which trees does Denver plant in place of ash?
| Tree | Why it suits Denver |
|---|---|
| Hackberry | Tough, drought-tolerant and at home in alkaline soil |
| Elm (disease-resistant varieties) | Fast shade and the classic vase shape |
| Kentucky coffeetree | Few pest problems and good drought tolerance |
| Oak | Long-lived, strong-wooded shade tree |
| Catalpa | Large leaves, summer flowers and quick growth |
The species list comes from Be A Smart Ash’s free tree program, which says it tries to plant large shade trees as spacing allows. The notes on each tree are general guidance.
Why not plant just one kind of tree?
Emerald ash borer is so damaging because ash was planted everywhere. Be A Smart Ash explains that planting the same species in lines along streets has given way to choosing trees that are hardy, add diversity and resist local pests, so that one insect cannot take out a whole block again. Pick something your neighbors do not already have.
Is there an approved list?
Yes. The Office of the City Forester keeps a list of approved trees for the public right-of-way. Be A Smart Ash notes that the list was written for street trees but is useful for choosing a yard tree too. Planting in the right-of-way needs a free permit. See tree permits in Denver.
Where should the new tree go?
- Not in the old stump hole. Old roots and wood chips make a poor start. Plant a few feet to the side. See what to do after stump grinding.
- Away from other trees. The city’s free tree program asks for 35 feet from large shade trees and 25 feet from ornamental trees.
- Clear of wires. Put large shade trees where they will not grow into power lines.
Can you get a free tree?
Possibly. Denver plants free trees in the right-of-way for residents who have the space, and The Park People’s Denver Digs Trees program offers free or low-cost yard trees. Details are in Denver’s free tree and ash replacement programs.
Should you plant before the ash comes down?
If you have room, yes. A tree planted now will have several years of growth by the time the ash has to go. Whether to keep the ash in the meantime is covered in should you treat or remove your ash tree?
Ash replacement FAQs
Can I replace my ash tree with another ash?
It is not recommended. Be A Smart Ash states that further planting of ash trees in Colorado is not recommended, because any new ash would need treatment for life.
What is the best shade tree to replace an ash in Denver?
Hackberry, oak, Kentucky coffeetree, catalpa and disease-resistant elm are the large shade trees Denver’s free tree program commonly plants. The best one for you depends on the space and on what is already growing nearby.
When is the best time to plant a replacement tree in Denver?
Spring and early fall, when the soil is workable and the tree has time to root before summer heat or winter cold.
