Question
QUESTION: I and everyone on our street have a flowering pear tree on my park strip.  It was very well established when the home builder planted them four us 8 years ago.  I now want to put pavers on by park strip but there's a few roots growing to the surface approx 3 ft from the tree and will have to be removed.  The tree is now 25 ft tall and very hardy.  Will I damage the tree if I remove these few surface roots?

ANSWER: You can cut up to 25% of a trees root system without killing it. You may get some foliage dieback form cutting too many roots. You can estimate the system that would be cut by drawing a circle around the tree where the branches extend out to and then draw a line through this circle were the roots would be cut. IF the cut part exceeds 25% the tree will have a good deal of damage.

Another idea is add sand over the roots and put the pavers down on the sand this way the roots will not be cut and should be ok as long as you do not add more than 3 inches or so of sand. Sand is best since the water will drain through it better than clay or other soils.

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QUESTION: Jim,
Thanks for your reply.  I don't quite understand how I can estimate 25% of a tree's root system when it's all underground.  I must clear the roots away 9 inches below the surface on two sides of the tree thich I did yesterday but I don't understand how I can estimate how much of the total I took when so much of the roots are down deeper.
Any ideas?

Answer
The roots are in the first 12-18 inches of the soil. If you dug 9 inches deep on two sides of the tree I would say you damaged more than 25 % of the roots system (somewhere between 25 and 50%). This does not necessarily mean the tree will die but you can expect some foliage dieback on the side of the tree the digging occurred. IF the pavers are not solid I would suggest that you water the area heavily once a week until the first frost. Next spring I would expect that the foliage on that side will not be as full as the other side and you could have some branches die. The problem will be the root system left can not support the foliage of the original  tree and some will die to compensate. About all you can do now is wait and see what happens next spring.