Answer: Lots of things can stunt the growth of an oak tree. If broadleaf weed killers were used excessively in the area it could account for a small root system and therefore a smaller tree, but the chemicals might have just as well killed the tree outright. There's really no way of knowing exactly why your tree is acting the way it is. Perhaps the roots are girdling (growing around and around) because of the way it was planted. If the tree is puny you might consider just taking it out and replacing it with a healthy new oak tree. Good luck with your landscape!
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