Question
QUESTION: Don't know what type of willow neighbor planted, but they did plant it a foot away from the property line and I know (first hand) that willows can do some very serious damage to pipes and sewers and spoke with water company and we will be liable if this tree trunk were eventually grown out to our property and caused damage to the pipes and sewer.  So my question is, how large can the trunks of willow trees get?  My parents have 3 and the measured one at 16' and it's still growing.  

Sure hope you can help.

Thank you

ANSWER: Weeping willow can get about 30-40 feet tall at maturity and about 20-30 feet spread if growing in good soil. Willow roots can be a problem especially for septic type sewer systems but the newer sea;e sewer lines are usually ok unless there is a leak roots seek out water. The roots will grow about 1 1/2 times the width of the branches. This tree is too close to the line for it to reach its true form. To reach its nice weeping form it needs to be planted out in a pretty good size yard in an open space.  I would ask the neighbor to please move it because you do not want the limbs and foliage growing onto your property and will need to prune them back which will make the tree look lop-sided and not too pretty. It should be moved now while it is small. If they will not move it prune your side. You could also install a root barrier along your side which would keep the roots from growing your way but this is an expense--I would prune and/or maybe trench along the line about 12-18 inches deep and fill with sand and every couple of years re trench cutting the roots that grow your way. Yes this may damage the foliage on your side but it will keep the roots growing away from you. Moving the tree is best followed by the pruning and then the trenching.

---------- FOLLOW-UP ----------

QUESTION: Do you know about how big the TRUNK can get and a what rate?  My neighbor was already told that they should move, but they have not.  And I have been reading on line about property owners and trees and if a tree trunk is to grow on two properties, then they are co-owners even though one party didn't want it.  I just really need to know how large the trunk can get, so I can put in(if needed) a complaint.

Answer
The diameter will depend on the kind of willow but generally they can reach a diameter of about 18-30 inches at maturity. The rate of growth will depend on the soil conditions and the growing conditions (water etc). I would say a tree planted a foot from the line the trunk will grow over the line sooner than later. If you fertilize your lawn near the tree with a granular fertilizer called Weed and Feed this will kill the tree. Weed and Feed has a herbicide in it that will damage and/or kill a tree.  If the tree is not moved then fertilize the grass on your side with the Weed and Feed. But do not put this out near trees not wanting to be damaged.