Can Hydrangea Roots Damage Underground Pipes?

Root Behavior Near Pipes

A plant root cannot distinguish between a water pipe and a rock. Roots only invade pipes if they leak water. An irrigation supply pipe is unlikely to leak, but a sewage drain pipe might.

Hydrangea vs. Tree Roots

Your hydrangea's roots will not harm the gas or irrigation pipes you encountered. However, a tree planted over pipes could eventually damage them as its roots swell and gradually bend the pipe.