Answer: Suckering is just an individual characteristic of certain trees. There are some trees that will always sucker out away from the tree, popping up all over the yard. Aspen and some of the poplars are like that.
Other trees, such as chokecherries, have a tendency to want to always sucker right at the base of the trunk. This type of plant really wants to grow as a large shrub or a small, multi-stemmed tree; we try to force it to grow as a single stem trunk.
Other trees will occasionally sucker at the base. Apple trees are probably the best example. Many apple trees grow fine with few, if any, suckers, while others sucker and sucker and sucker! This often goes back to the type of rootstock the tree was grafted on. Again, it's connected to the individual characteristic of that plant; certain rootstocks have a bad tendency to sucker a lot.
Having said all that, most plants rarely, if ever, sucker. When they do, it's usually in response to a wound to the roots or perhaps something that's damaging the top of the tree. If there's some injury to the trunk, whether due to physical injury or some insect or disease problem, it's normal for the tree to push out suckers below this injury, even suckers from the roots.
The tree is trying to heal the injury or bring back the "root to shoot" balance. The top needs the roots to absorb water and nutrients, while the roots need the foliage to manufacture carbohydrates through photosynthesis, which feeds the roots and enables them to function as they should. If some injury occurs to the tree disrupting this balance, the tree will work to restore it by growing new shoots to replace lost ones.
As long as your tree is happy and healthy, the suckering that you're seeing is probably just part of the nature of that particular tree. Most people just keep cutting the suckers off. An alternative is a relatively new product called Sucker Stopper. It's manufactured by Monterey Lawn and Garden Products. We don't have a lot of experience with this product, but it sounds like it may help a lot with this problem.
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