Last week a neighbor of mine called me up to ask how likely it was that their 4 year old (or so) crab apple tree was dead. Sometime over the course of the winter cute fuzzy bunnies had decided that the tree’s bark was tasty and decided to eat it. Naturally they ate it all the way around the circumference of the tree with the exception of a strip about an inch wide. At this point you’re probably asking yourself why the neighbors suspected the tree might be alive. The reason they were calling me was that the tree was leafing out– so they figured that maybe the tree would make it — that maybe, just maybe, it wasn’t as bad as it looked. My answer — Sorry, the tree is dead, it just doesn’t know it yet. As a rule of thumb you can have up to a third of the circumference of a young tree girdled and the tree has a decent chance of growing out of it. More than that and, though the tree might live for a few years, you’re dealing with so much damage to the vascular tissue that you’re just putting off the inevitable by not cutting it down. A tree with as much damage as my neighbors tree had was just going through the motions.
When bark is eaten what is destroyed is the phloem — the tissue which carries the carbohydrates made by the leaves down the plant’s stem. The cambium — which creates new phloem and xylem — is also destroyed. But the xylem — the innermost tissue which transports water and nutrients up the stem — is left largely intact. So girdled trees will flush out in the spring (using resources provided by the xylem), perhaps even two springs, but ultimately the tree will succumb.
But there is an up-side! Girdled trees will be under a lot of stress. Stressed trees tend to flower heavily — so enjoy the show first, then cut down the tree.