I am considering installing a concrete patio in between four large Cottonwood trees. It will be a slab that does not require much excavation, perhaps about six inches at the most. The edges would be about 2-3 feet from the trunk of any of the trees. My question is this; do I need to be concerned about the trees getting enough water since the slab will block a small portion of the tree from getting water that would formerly be soaking into the ground? The trees are over 40 years old.

Thank you.

Jim Cell 612.306.3141

It is difficult to tell what damage may occur to the trees.  First there will be soil compaction which will affect the trees ability to maintain roots.  A general figure is that a tree may lose 25% of root structures without killing it. But you need to measure not from the trunk but from the dip line as described at the following website.  See: https://conservancy.umn.edu/bitstream/handle/11299/199785/Protecting%20trees%20from%20construction%20-%20a%20homeowner%27s%20guide%20_%20UMN%20Extension.pdf?sequence=1&isAllowed=y

Cottonwood trees are shallow rooted trees so you will damage the root structure.  Another consideration is that Cottonwoods produce very strong roots that are capable of breaking concrete. See: https://aces.nmsu.edu/ces/yard/2008/091108.html

I recommend an onsite evaluation by a tree care professional to evaluate the particulars of your plan.  See: https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional



You are welcome.