Paving under a tree canopy - Ask Extension
Hi,
Thank you for taking my question.
We have a very small yard in central Denver with a nice, big Water Birch tree that we like to sit under. We w...
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Paving under a tree canopy #876961
Asked July 12, 2024, 11:58 AM EDT
Hi,
Thank you for taking my question.
We have a very small yard in central Denver with a nice, big Water Birch tree that we like to sit under. We want to put a patio under part of the tree, for our table and chairs, using some large sidewalk flagstones set on sand. We thought it might be good to put drip irrigation in the sand layer to make sure the roots get enough water. We are worried that the roots might not get enough air though. Is there a way to get air under there with perforated pipe?
We'd like to find an arborist who specializes in the care of existing trees who could advise us about whether or how this patio might affect the tree and how to minimize harm if it is possible to do the patio. The tree companies I am finding specialize in pruning and removal not so much this kind of advice.
Denver County Colorado
Expert Response
Thank you for your question. The photos indicate a very small space very close to the the trunk of the tree. Putting a drip system would create pockets of water but not evenly distribute the water to all areas of the roots. It is a beautiful tree that requires frequent watering especially in this heat. Not sure a drip system would deliver adequate water to the root system. You might want to consider a mulch cover with strategically placed flagstone paver but keeping the area open for the most part for air and water. That tree requires more water than most. The more air and water restriction the more likelihood the tree would suffer damage. We are not aware of anyway to get air to roots other than through the surface area.
Thank you so much for your answer to my questions.
I think the space under the tree may be larger than the picture shows well, but it IS all under the tree canopy, about 14’x14’ to the south of the trunk.
I have changed my under-tree-patio-plan to using 2” geo cell filled with crusher fines. That will give us a stable, firm surface that is permeable to water and air. I’ll run drip lines under it for convenience since there is no longer much danger of overwatering (I was worried water might get trapped under the stones without me knowing).
Do you see any downsides to this idea?
Thank you again!
Andrea
303.860.0463
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I really don't like the idea of crusher fines over the root bed of the tree. Fines are not as permeable as you might think. They compress into a surface as hard as concrete over time. The geocell would help some, but use will eventually lock the fines together into something that is not permeable. In my opinion, the best solution, although more expensive, would be a deck. Anything installed directly on the surface of the ground will adversely affect the tree's roots access to water, air and nutrients, all of which are necessary for tree and root health.
