Answer: I wish there were an easy answer to your question. As a general rule of thumb, the roots of a mimosa will be concentrated in the top 18-24 inches of soil and extend out one and one-half times the diameter of the canopy. I've never heard of a case where mimosa roots have lifted a driveway or sidewalk, but it is possible. You can encourage the roots to grow deep by watering deeply, which will probably keep them from remaining close enough to the surface to cause damage. Deep watering can be accomplished by building a watering basin around the tree when you plant it (pile a few inches of soil up in a circle about 12 inches from the trunk). Plan on watering once each week by filling the basin, allowing it to drain, then filling it a second time. Watering in this way will concentrate the water over the roots and allowing it to trickle down and wet the entire root mass. Best wishes with your mimosa!
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