Question
My suburban Philadelphia, PA neighbor contends that the root system of a weeping willow I just planted will kill off their very extensive backyard garden, on the other side of the fence, within two years. True? If so, would it damage anything within six months or one year? Thanks very much.

Answer
The roots will not kill off the garden but they will grow that way since the garden will more than likely be watered and fertilized. Willows seems to grow their roots toward a water source and the garden will be a place they would grow toward. Root barriers can be put between the tree and the garden stopping the roots from going that way but the annual tilling of the garden will kill the roots that are there but this may damage the tree. The shade from the willow will be the biggest deterrent to the garden.
If you want the tree there I would suggest that root barriers be installed along the fence--suggest that you split the cost with the neighbor.

Here is one web site that sells root barriers. Most tree nurseries will have information on the barriers.
http://www.rootsolutionsrootbarrier.com/root-barrier-installation.htm