Quick answer: Pull Siberian elm and tree-of-heaven seedlings while they are small enough to come out by the root. Larger ones have to be cut down and the stump ground out, and any new sprouts cut off repeatedly until the roots are exhausted. Cutting alone does not work: both trees resprout from the stump, and tree-of-heaven sends up shoots from its roots as well.
These two weed trees fill the gaps in Denver yards: fence lines, alleys, window wells and the edges of garages. This guide covers how to identify and remove them. For larger jobs, see land clearing and brush removal in Denver.
How do you identify them?
| Siberian elm | Tree-of-heaven | |
|---|---|---|
| Leaves | Small, single, toothed leaves | Long leaves made of many leaflets, each with a small notch near its base |
| Seeds | Papery discs that blow everywhere in spring | Clusters of twisted, winged seeds in late summer |
| Smell | None | Strong, unpleasant odor when a leaf or twig is crushed |
| Growth | Very fast, with brittle wood | Very fast, with soft wood and thick shoots |
Why are they a problem?
- They seed everywhere. One mature tree produces thousands of seedlings a year.
- They grow where they should not. Against foundations, through fences and into sewer lines.
- They break. Siberian elm is among the worst trees for snow damage. See which trees break most in Denver snowstorms?
- They come back. A cut stump sprouts within weeks.
How do you remove them, by size?
| Size | What works |
|---|---|
| Seedlings, up to knee height | Pull by hand after rain or watering, roots and all |
| Saplings, up to wrist thickness | Dig out with the root, or cut and grind the stump |
| Established trees | Tree removal, then stump grinding |
| Sprouts after cutting | Cut or mow them off every time they appear |
For established trees, see tree removal in Denver and stump grinding. Why a stump should not be left is covered in should you leave a tree stump?
What about herbicide?
Herbicide applied to a freshly cut stump is the most reliable way to stop regrowth, especially for tree-of-heaven. A homeowner can use a product labeled for that purpose on their own property, following the label. In Colorado, anyone paid to apply pesticide must be licensed by the Department of Agriculture, so check a company on the state’s applicator search if you hire that work out. We cut the trees and grind the stumps.
How do you stop them coming back?
- Walk the fence line each spring and pull seedlings while they are small
- Remove the mature seed trees on your property if you can
- Cover bare soil with mulch or planting so seeds have nowhere to start
- Keep cutting sprouts. Each cut drains the roots
When is it a clearing job?
When a whole fence line, alley edge or back corner has gone to thicket, it is quicker to have it cleared in one visit. That is brush removal: see land clearing vs. lot clearing vs. brush removal and land clearing cost in Denver.
If you are clearing the lot to build on, see how to clear a lot for building in Denver.
Siberian elm and tree-of-heaven FAQs
Will a Siberian elm grow back after it is cut down?
Yes. The stump sends up vigorous sprouts unless it is ground out or treated. Sprouts have to be cut off repeatedly until the roots run out of stored energy.
How do I know if a tree is tree-of-heaven?
Crush a leaf. Tree-of-heaven has a strong, unpleasant smell. Its long leaves are made up of many leaflets, each with a small notch near the base.
Is it worth keeping a volunteer Siberian elm?
Rarely. They grow fast but have brittle wood, break in snow and seed heavily. A volunteer growing against a fence or foundation should come out while it is small.
Sources
This guide is based on standard arboricultural practice. For pesticide licensing, see the Colorado Department of Agriculture applicator search.
