Although there are some problems associated with fastening a fence to trees, sometimes it is the most expedient way to get the fence built. This is especially true when the area to be fenced has lots of trees, as the roots interfere with setting posts, making construction very difficult. If you are going to build a fence and find it necessary to fasten it to trees, it can be done in a way that gives you a strong fence and does not harm the trees. Field fence is one of the best fencing types for such a project.
Wrap each part of the fencing that will be touching the tree with cloth. The fabric provides a barrier to prevent the wire from digging into the bark of the tree and causing damage.
Attach the bottom wire to the lowest part of the tree possible by hammering in a fence staple to hold the wire. The size of the staple you use will depend on the tree and how rough or smooth its bark is. Fences attached to trees usually do not fit close to the ground, as the trees roots interfere with a tight fit. However, in most cases you can get the fence low enough to keep out all but the smallest animals.
Pull the fencing up, making it as tight as you can vertically along the tree. Staple the middle wire tightly to the tree. Repeat this process for the top wire.
Move to the next tree or fence post down the line. Make sure the wire is stretched tight between this post and the tree, and attach the fence to this post.
Return to the tree and check that the fence is properly stretched from bottom to top. There should not be any kinks or folds in the fencing. Fasten the rest of the horizontal strands to the tree by pounding in fence staples to hold each wire.
Repeat this process for any other trees in the fence line. Always stretch the fencing from the bottom to the top, so that you don't end up with any fencing folded onto the ground.
When you fasten fencing to a tree, the fence will loosen as the tree grows. Trees get bigger around, but they grow from the top, so the places where your fence is attached will stay at the same height, but they will be pushed outward as the tree gets bigger around. Check the fence every year and tighten it as necessary.
If you sink bolts deeply into a tree for any reason, you may cause harm to the tree. Wrapping wire around the tree can strangle the tree and cause it to die.