Q: I recently planted a hydrangea bush next to my house. When I was digging the hole I found a gas pipe and an irrigation pipe directly underneath. Do I need to worry about the roots damaging these lines as the hydrangea grows?
A: A plant root can’t tell the difference between a water pipe and a rock. The only reason a plant root might invade a pipe is if it leaks water. That’s not likely with an irrigation supply pipe but might be possible with a sewage drain pipe. Your hydrangea roots won’t hurt the pipes you found. On the other hand, a tree planted over pipes might damage them due to the tree’s roots swelling and gradually bending the pipe.