by Steve Turner
Over the last couple of years, my Norway maple seems to be getting thinner, getting its fall color early, and some limbs are dying on one side of the tree. What’s wrong?
Unfortunately, the situation does not look good. From what you have described, it sounds as if your tree has girdling roots, which is a major problem of Norway maples and ‘Crimson King’ maples, a cultivar of the Norway maple. Many of these trees develop the problem between 25 and 40 years of age, which is also when the tree starts to mature and become the picture perfect tree we all admire. If you look closely at the base of the tree, you will see that instead of your tree having “root flare” as it goes into the ground, it looks more like a telephone pole going straight into the ground or it has a flat side instead of being round. These are sure signs that the roots below are wrapped around the trunk and are causing a slow, but certain death by strangulation for your otherwise perfect maple.
The reasons for this are a little more complicated. The problems begin in the nursery when the trees are dug for transplanting. The process of digging severs tree roots, which in most trees is no big problem. But with Norway maples, this causes a major change in the way the root system develops. In the tips of the roots is a growth regulator that causes all the roots behind the tip to remain smaller than the main root which extends away from the tree. When this root tip is severed, the tree loses its ability to control the size of the lateral roots, and that is where the trouble begins. The lateral roots become dominant and cross the trunk of the tree causing the restriction that eventually brings the demise of the tree. It’s no coincidence that the size of the trunk at the time of decline is usually the size of the original root ball at the time of planting, which is why it takes so long to discover the problem.
Unfortunately, there is no cure. Fertilization will only speed up the growth of the tree and cause it to die sooner. Cutting the roots is expensive and is not a permanent solution; they will grow back in time and then you are back to square one. Keeping the tree well watered will help prolong its life, but it is not a cure.
Steve Turner, Certified Arborist, is from Arboricultural Services in Ferndale, MI.