Question
Hi -
Thank you for reading my mercy.  I have an approx 20 ft (20-30 years old?) Japanese maple that just got injured today (11/02/09).  A plummer, against our instructions, decided to dig a 4 ft deep hole (2 by 3 feet wide) and approx 5 inches away from the Japanese maple's tree trunk to access our home's sewer line.  How much damage did this do to our loving tree (one of the main reason why we bought our house)?  Is there anything we can do to treat it?  Is there hope for the tree?  Or should we expect the worst?

Our Japanese maple is approx 20 ft tall, 20 ft wide, about 4 feet away from our house, unknown age.  Truly a beauty.

Thank you so much for your help and input.

Grieving Japanese Maple owner,
N


Answer
Since it is a hole and not a trench it may not be too bad. You can get away with damaging up to about 25-30% of the root system without causing major damage to the tree. The percent is measured by the amount of surface area dug under the spread of the branches. Say you draw a circle around the tree where the limbs extend out to and then calculate the amount that was dug up if this area. if it does not exceed the 25-30% the tree should be ok. The worst case would be that the tree would lose some foliage on the side near the dug area. I do not think you will find a very large percent that was cut.
I would since the digging was this near the trunk I would watch the area of the trunk for signs of borer attack and if this shows up treat the tree trunk with an insecticide for borers. Ask you local nursery for an insecticide for maple borers. Since it is late in the year I would not really expect this to happen but I would be on the look out next spring.