Root system of an evergreen tree

Question

We have evergreen trees that are approx. 55 feet tall. I am not sure the name of this type of evergreen, but is has short needles and the branches fall like a canopy and produce very small pinecones. Next door to our property they are intending to build right next to our property line where the trees are and we are concerned about damage to their root system. We have been here for 30 plus years and love our trees. The questions are: (a) how far does the root system extend?; (b) what can be done to protect the root system? (c) if they dig so close to the trees would it be likely that they will die?

The area the new trees would be planted face north, they get some early morning light and afternoon light. Not sure about the soil, but there are scattered trees in this area already but not as a border, so there are quite a bit of root system in the area, but the new trees should be planted a couple of feet away from the existing trees. The trees would be along the back of the lot and our lot is approx 63 ft wide. Also, if we would request 2 lines of trees for privacy/noise levels, do you think that is feasible or how far do such big trees need to survive?

One other question I have is if we want to plant additional trees to line the property line, are there fast growing columnar evergreens for privacy that we can plant or what type of tree could we plant for privacy as they are building a 3 storey, 36 foot tall building right beside our property line which apparently will be 40 foot wide.

Answer 1

For many years it was thought that the majority of roots extended as far as the drip line, that is, the point where water falls off the foliage that is furthest from the trunk.

Further research has shown that the answer is "it depends". Soil profile, urban or rural area, species, density of trees, age of trees all play a part.

Even if we knew the type of tree, age of tree, soil profile and spacing it is difficult to tell as roots do not grow uniformly around a tree.

About the only thing you can say with certainty is that the closer to trunk the more roots there are.

You can do some fieldwork yourself by getting out a shovel and making a series of sharp cuts in the turf on your property line. When you dig down six inches do you see tree roots?

As to whether your trees will die it depends on the percentage of the root area that will be disturbed. If more than half of the root area will be disturbed then there is a good chance that the health will suffer. Most trees don't take well to the compaction that is common with construction. If possible ask the neighbour to use construction fencing to ensure that the root area on their property is not driven over by machinery.

Regarding selecting a new type of tree we need more details as to your location, amount of light, soil type and size of the planting area in order to assist.

Answer 2

Will the next door building be piled or have a ground floor slab foundation? If it's piled, there can be less ground disturbance - as long as the contractor has been made aware to disturb minimally. If piling is the method - would you be able to discuss this with the neighbour?

Even with a slab there are (cost effective) ways of protecting your trees but only if the neighbour is a little flexible.

When I start trees jobs I use this as a protection basis (adapted from a British Standard)

1. Measure tree diameter at breast height (dbh) and divide sum by 25,
2. For every 25mm increment of trunk diameter increase the protection radius by 450mm from the centre of the trunk
3. Thus a 1200mm trunk yields a 21.6m diameter protection zone

And yes where do you live (roughly)?

Answer 3

10-12 inches of course mulching protect roots from equipment. In some states there are laws which protect a tree from destruction by a neighbor. For instance, the neighbor can prune branches over their property, but not so much that the tree dies.