Question
When building a new subdivision road and planting new trees in the tree belt, Planning Boards ask for a root barrier so that the roots do not go under the sidewalk and under the road. Is there a fabric which can be useful instead of those rigid plastic barriers that I see advertised? I thought years ago I saw geotech (fabric) materials with nodules of chemicals which kept roots away and made them go downward or in the other directions. Has this been taken off the market.

Answer
Here is web link to one of these type. http://www.biobarrier.com/biobinfo.html

This material is a thin plastic fabric containing small dots of hard plastic. These plastic dots are impregnated with an herbicide which will not kill the tree but will stop growth of roots as they approach the barrier. This chemical is usually trifluralin herbicide. This herbicide is not absorbed into the plant and translocated; therefore, it does not kill the rest of the plant. It has only low solubility in water and doesn't wash away to other places. This means it will stay in the region of the root barrier and not interfere with the growth of roots elsewhere. This method of root control will involve the least effort (trench one time) and should give many years of protection. Since you are planning to create a root barrier at the time you plant the new tree, you will not harm the tree when installing the root barrier.