Root Risks of Purple Robe Locust Near Sewer Lines and Driveways

Rootstock Issue

Purple Robe locust is grafted on black locust rootstock—known for aggressive roots lifting pavement and invading sewers.

Guidelines

• Sewer lines: Keep 12+ ft away (3.5 m).
• Driveway/sidewalk: Roots extend 2× canopy width.
• Move now if possible while tree is small (2 years planted).

Key Takeaway

Black locust roots are problematic for hardscapes and utilities. Relocate young grafted locusts early.