Is it a good idea to put down plastic sheeting or "weed barrier" fabric to stop weeds growing up in a tree box?

Plastic sheeting actually harms the tree and is forbidden by city law. Plastic sheeting and even weed fabric, which is perforated, will stop or severely limit water from penetrating into the soil. The tiny perforations that are supposed to make most weed fabrics permeable get clogged with silt and do not let adequate amounts of moisture through. Without sufficient water, your tree will decline and eventually die. The importance of not laying weed barrier fabric or plastic cannot be overstated; street trees have enough stresses with which to cope, adding another may cause enough harm to kill them.  more