Answer: Southern magnolias can reach 80' tall and 60' wide at maturity. It's not unusual for surface roots to reach one and one-half times as far out as the edge of the canopy. If you're planting one of the larger magnolias, keep it between 60' and 90' away from a fence line. If you don't have that much room, try planting one of the smaller Southern magnolias such as 'Samuel Summer' or 'San Marino'. These typically reach only 20' wide at maturity.
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