Question
We need to install a french drain which will run about 2 ft deep. I have a Pin Oak Tree about 20 feet from where the drain will be installed and several pine trees within several feet of the proposed drain. My question is, will this damage the root system of my trees to the extent that the trees will may die? I am particularly concerned with the pin oak.
Thank you,
Kaye

Answer
You should not have any problem with the pin oak--they have a spread of about 25 feet when mature so the 20 feet away will not be within the major root zone.
The pine may have some problems. The general rule is not to cut more then 20% of the root system and the tree will not be effected. If you draw a circle around the tree where the limbs extent out ot and the trench does not cut through this pie shape and cut more than 205 there will be not problem.  Several feet may cause the tree to loose some of it foliage on that side of the tree. Pines do have a tap root system so the cutting of side roots is not as bad as if the tree were a hardwood tree. The tree will more than likely not die but you can expect some branches to die on that side of the pine.