Answer: The three foot size is an average after about ten years. Over time, it may grow slightly larger, usually running a bit wider than tall. The actual size will depend on the growing conditions where it is planted. This shrub is so slow growing that should pruning ever be needed to control size, it would a minimal, infrequent task. Here is the Pennsylvania Horticultural Society description of it: (You may need to cut and paste the complete url into your browser to make it work correctly.)
I hope this helps.
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