Question
My neighbor planted a magnolia tree, 5 feet on the other side of a fence, near my swimming pool. I am concerned about the roots coming under the fence and damaging my swimming pool. It is a fiberglass glass swimming pool. thanks

Answer
Magnolia trees has the potential for getting quite large (30-40 ft. ht. %26 about 20 feet wide - depending on your climate %26 other factors).  This will mean the root system will be about 25-30 spread from the trunk. The majority of the roots will be in the first 2 feet of soil and will be the size of medium ropes. The roots have the capability of lifting sidewalks and patios and I would expect since the pool is fiberglass the roots will not be able to penetrate the pool. BUT this tree has the problem of dropping leaves all year long and the trash will get into the pool. You can install root barrier along the fence to stop the roots but the leaves are another thing. Any roots coming on to your property can be controlled by cutting the roots and painting the cut with a herbicide called Roundup. This will kill back the roots but may cause some damage to the tree. I would ask the neighbor to please move the tree this Fall to a place that will not interfere with the pool. Here is a web link to root barriers. http://www.4specs.com/s/32/32-9452.html