Answer: A healthy, well cared for Leyland Cypress should not develop root problems nor should the roots grow above the soil. Your soil is sandy and therefore should be easy for the roots to penetrate. I don't think the roots will grow above the soil line and because of this I don't think they will be susceptible to root knots. Keep your tree well watered by watering infrequently but deeply and the roots should grow down, not out and up. Best wishes with your new tree.
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