My neighbors are having a field system dug for their septic system. The digging is just beyond the edge of the drip line of my very tall, 60+ years old, Norway spruce. Will my tree suffer any consequences of these trenches being dug? We have had a very wet spring but the trenches were left open over night. I am concerned that major roots could have been damaged or destroyed and that leaving the trenches open may cause dry out of any roots remaining. Could there be ramifications later?

2 Answers 2


Tree roots extend a lot farther than the drip line but soil type and tree species affect this as well.

Yes, roots have been severed and you may see some dieback or lack of growth on that side of the tree later this season and next spring.

How much of a problem depends on a number of factors including the health of the tree and how much else is changed at the same.

At this stage you cannot prevent the damage but you can make sure further damage is prevented or minimized. Mature trees like things just the way they are:

  • ensure that the work being done does not change the grade or height of soil near the tree
  • hopefully the work will not change the drainage
  • prevent any damage to the trunk. Wrap it in plastic mesh fencing if you think this is possible
  • prevent heavy machinery from compacting the ground under or near the drip line
  • 2
    You can take great pride that in future, the tree will take revenge by growing its replacement roots into the drainfield and clogging up the works... Fortunately for them, it will be in a decade or two. Jul 3, 2015 at 3:56
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    I have a lot of big norway spruces. They are tall narrow trees, but they have a very wide, shallow root system, and many of my trees have surface roots over 2" in diameter more than 20' out of the dripline. They are kinda sensitive, though, and get root rot very easily in constant wet. Several norway spruces in my neighborhood died last year, from the bogginess we had here. Honestly, a drain right next to them will probably not show any signs right away, but the trees will probably start to slow down/deteriorate over the next decade.
    – J. Musser
    Jul 8, 2015 at 3:35

It would be best to send a picture of what you are trying to explain...generally the open trenches will not adversely affect this tree. Cutting roots is fine and also enhances more fine root growth as long as the damage is limited to less than a third of the 'pie'...thinking of the circle around a tree to include its drip line.

The biggest problem is the level at the base of the tree. It HAS to stay where it was...even soil mounded up on the tree 1/2 inch!!! will cause bacteria to 'girdle' the vascular system that is just below the bark. This will kill a tree so easily...maybe 6 months up to a few years. Has construction equipment been running over the soil around this tree? Compaction is a big problem and I would worry about my tree way past its drip line (where its canopy sheds rain). Again, how much of its 'pie' has been compacted? Is there a fence? Don't wrap the trunk of this tree unless it is VERY TEMPORARY, LIKE a few days max! Are your neighbors changing the GRADE of their landscape in relation to yours? For instance, making mounds, installing septic fields, water features? Please send pictures! Mature trees are worth thousands of bucks! The laws get pretty confusing. Best to get this recorded, photographed and discussed (with your neighbors) BEFORE problems arise and well...you lose your neighbors as friends!

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