One of the damages professional arborists see the most frequently on trees is strangulation. Someone long ago staked the tree and simply never removed the wire. Or installed a hammock or a clothesline between two trees using a rope and now the rope is eating into the bark. There are dozens of other reasons why someone might think wrapping a restricting device around a tree might be a good idea, but the fact remains: this is never good for woody plants and could eventually kill the tree.
Trunks Expand, Wire Doesn’t
It is important to understand that tree trunks increase in diameter as they grow. So do branches. So if a cord, a wire or even a supposedly safe tree tie is attached around a trunk or branch and stays in place too long, it will cause damage. The bark will start to grow around it, leaving a permanent mark. Worse, if left too long, the restriction will keep sap from flowing through the tree, eventually killing all growth above the constricted part. This is especially annoying in that it can take years to finally kill the tree and losing a long-established tree is not something anyone wants to see happen.
What to Do?
First, never leave a tree staked very long: normally one year is the most you’ll ever need. So, when the time is up, just unwind the cord or wire or cut it free. The faster you remove the stake (and the wire), the better.
If you have a good reason to leave the stake on longer, at least move the wire or cord to another spot each spring. Also, there is never a need to tighten a wire, cord, or strap around a trunk or branch. Even a staked tree should be able to move at least a bit in the wind.
So much for staking, but what if you want to fix something permanently to a trunk (hammock, clothesline, signage, etc.)? Wrapping a cord or wire around the trunk is never a good idea unless the installation is to be temporary. Even inserting the wire into a section of old garden hose, supposedly to keep it from digging into the bark, will only protect the trunk for a few years: it will cut into the bark if left on permanently.
Instead, don’t hesitate to screw a hook or an eyelet into the trunk. No, it will not cause major damage to the tree: inserting a metal stem into a trunk is no more harmful to the tree than having a ear or nose pierced is to humans.
That’s sounds suspicious? Visit a botanical garden or arboretum and take a look. They don’t hesitate to screw identification plates into the trunk of a living tree. If scientists do it, you can too.
Whatever your need, the important thing to remember is simply to not strangle the trunk or branch with a permanent wire or cord.