Root depth Crab and Dogwood
 

I planted a long line of White Dogwoods and Robinson Crabapples only a
foot
and one-half away from a ditch. The ditch has a plastic drain pipe
covered by
trap rock. The pipe carries runoff ground water to a catch basin. WILL
THE TREE ROOTS COMPROMISE THE DRAINAGE SYSTEM by invading the pipe? HOW
DEEP do the roots of these two trees go down? The pipe is no less than
20" deep. Our condo board needs assurance that all is well, or I'll have
to move all of the trees.
Thanks