I’m having a problem with a neighbour’s tree. The roots have found their way into my drain pipes and caused a blockage. I’m legally entitled to cut any roots on my property (and overhanging branches)- with some provisos.
My question is, does pruning branches of a tree help to inhibit its root growth. Is there a “tie- up” between roots and branches, or does the tree just grow above and below ground willy nilly.
Obviously I want to do anything legally possible to prevent a recurrence of damage by the roots.
I should say my neighbour refuses to cut down the tree.
Instructions for use of products, such as Jobe’s Spikes (tree fertilizing spikes), will show a diagram of a tree indicating the roots grow as far out as the branches.
I guess you’re asking if the roots would grow back if you don’t cut the branches back, too? However, I suspect cutting the branches will not impact those existing roots causing your problem.
Don’t know if this helps any. Consulting some gardening books about tree care may give you the full story, or ask around at your local garden center. - Jinx
Cutting the branches won’t eliminate the root problem you are having, but it could reduce the amount of water the tree needs and reduce the problem slightly. Since you would only be cutting ‘your’ side, I don’t think you would get much benefit from the trim. The whole tree really needs to be done properly to have the most effect.
A better solution would for you to install a ‘root barrier’ on your side of the property near your pipes. This is not usually harmful to the tree and could save your pipes and your foundation from root damage. Barriers are not too hard to install. The worst part is the digging. I would recommend renting a tiller or hiring a landscaper to do it.
IANAL, and you will want to investigate your rights with respect to a tree on a neighbor’s property.
As a *very * general rule, yes, there is a correspondence between branch spread and the root system. If you cut roots back, the branches and leaves above will put an increased demand on the remaining root system to provide water and nutrients. This can stress the tree, potentially killing it.
If you look at the branching of a tree, the circumference at the extent of the outer branch tips is called the “drip line”. In general, any root cutting outside the drip line has a negligible effect on the tree. Any cutting within the drip line should really be accompanied by a corresponding removal of brances above. You should take a look at the tree to see how severely you will be cutting back the root system.
As I mentioned, if you cut roots without removing branches, you may threaten the health of the tree. This may be worth discussing with your neighbor to explain why you want to do remove the branches. This work should really be done by an arborist, or someone who can prune the tree to maintain the health of the tree, and to retain the character.
However, with respect to your question: Cutting back branches will not by itself significantly reduce the root system.
Once the roots are trimmed, the root barrier may be a good idea to prevent this from happening again. What type of tree is it? Some tree roots can penetrate through building foundations.
The drip line thing is a good rule of thumb; however, some trees, such as locust and willow, have more aggressive roots.
Once you get your pipes cleaned out, there’s another way to keep tree roots from re-invading. Flush a tablespoonful of copper sulphate down the drain once a month.
Thanks for the replies so far.
To fill in a few details.
The tree is a Yew and is about 9/10 feet from the house, and the drain slightly nearer. The branches come to a couple of feet of my house. I’ve spoken twice to my neighbour and he was “not interested” in cutting it down, however I was also told by them I could cut the roots if I liked, and I’ve done that during the repair work to my drains. I also then spoke to my local council who said if the tree doesn’t have a preservation order on it I could cut the roots on my property as long as I didn’t endanger the tree.
I had cut the roots by then because I was anxious about my house foundations. I will have to speak to my neighbour again to see if he will agree to some pruning of the branches in his property to balance those I intend to cut on my side.
I suppose my question stemmed from the fact that if there was less demand from the branches the tree would tell the roots to take some time off and chill out. 
A couple of questions though.
What does the root barrier consist of?
Is Copper Sulphate a poison? How does it deter the roots?
Another note: the roots tend to seek water. That’s how they ended up in your pipes. If you heavily water the ground on your side of the fence, the root growth on your side will be more aggressive.