Cottonwood Surface Roots - Ask Extension
Hi There!I recently moved into a house that has a VERY large cottonwood in the front yard. This tree has many surface roots that are affecting the d...
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Cottonwood Surface Roots #475169
Asked August 01, 2018, 8:13 PM EDT
Hi There!
I recently moved into a house that has a VERY large cottonwood in the front yard. This tree has many surface roots that are affecting the driveway and sidewalk. Is it ok to cut the surface roots to mitigate any further damage and/or prior to replacing the driveway? If need be, I can send pics.
I recently moved into a house that has a VERY large cottonwood in the front yard. This tree has many surface roots that are affecting the driveway and sidewalk. Is it ok to cut the surface roots to mitigate any further damage and/or prior to replacing the driveway? If need be, I can send pics.
Jefferson County Colorado
Expert Response
Hello,
Cutting surface roots is not recommended, as they provide mechanical support for the tree as well as the 'pipeline' that transports water and nutrients to the crown. Tree roots are typically in the top 18-24 inches of soil, to give them access to oxygen, especially in the clayey soils of the front range. Some trees are more prone to surface roots ( Poplars/cottonwood, maples, elms, willow).
Consider some alternatives such as routing the sidewalk around the roots, and other options as described in "Trees and Sidewalks": https://www.umass.edu/urbantree/factsheets/22treesandsidewalks.html
If you must cut roots, cut as far away from the tree as possible (at least 2 feet)
Do not prune more than 25% of the surface roots. Additional recommendations from Washington State Univ: https://s3.wp.wsu.edu/uploads/sites/2076/2017/07/C137-Surface-Roots-15a.pdf
Cutting surface roots is not recommended, as they provide mechanical support for the tree as well as the 'pipeline' that transports water and nutrients to the crown. Tree roots are typically in the top 18-24 inches of soil, to give them access to oxygen, especially in the clayey soils of the front range. Some trees are more prone to surface roots ( Poplars/cottonwood, maples, elms, willow).
Consider some alternatives such as routing the sidewalk around the roots, and other options as described in "Trees and Sidewalks": https://www.umass.edu/urbantree/factsheets/22treesandsidewalks.html
If you must cut roots, cut as far away from the tree as possible (at least 2 feet)
Do not prune more than 25% of the surface roots. Additional recommendations from Washington State Univ: https://s3.wp.wsu.edu/uploads/sites/2076/2017/07/C137-Surface-Roots-15a.pdf
- While root pruning is often the first action people take in this situation, this should only be
used if a structure such as a walk or foundation is in danger. Be aware that permanent
damage to the tree will result from this action.
- If root pruning is necessary, follow these
guidelines:
- do not remove more than twenty-five percent of the functioning roots under the tree canopy
- root prune in the cool weather of late winter or early spring when there is less danger of dehydration
- Do not root prune after trees break bud in the spring, as this will deprive the tree of water when it needs it the most.
Two other good references:
- Trees and Sidewalks: https://www.umass.edu/urbantree/factsheets/22treesandsidewalks.html
- Tree Root Myths: https://www2.tntech.edu/tlcfortrees/tree_root_myths.htm
