Answer: Based on your description I am not certain quite how the tree is growing. It is not uncommon to have a stewartia that is grown as a multi-trunked tree or very large shrub in the 15 foot range, so what you are seeing may be normal. If however you have a tree with a single trunk with good caliper that is suddenlly sprouting new shoots from the roots, then that would be abnormal. It could indicate there is a problem underground with the roots or some other type of stress. Since I am not able to see the tree and its growing site, I would strongly suggest you consult with a professionally trained nurseryman at the retailer where you purchased the tree, and/or with your local county extension, and/or on site with a professionally trained and certified arborist who can help you determine what is happening and why, and based on knowing that, advise how to proceed. I'm sorry I can't be more specific for you.
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