Answer: The roots of your new trees will be concentrated in the top 18-24" of soil, but will travel out to at least the dripline of the canopy. Planting them only 4-5' away from a sidewalk can lead to problems as the trees mature. The roots could cause the sidewalk to buckle - but not for a few decades. If you get your trees off to a good start by watering deeply, you'll encourage the roots to go deep rather than remaining near the surface and growing outward. This may put the majority of the tree's roots too deep to be of problems to the sidewalk. Or, if you have another spot in your yard to plant them, you may opt to plant them where they won't cause problems as they mature.
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