I have two dogwood trees that is around 8 feet tall after 20 years. Although
I don't know the exact type of dogwood, all the literature I have read on
dogwood say they grow to 15 to 20 feet tall.

This suits me just fine, because I don't like large trees anyway. I would
like to plant another tree just like that. Is it easier to just buy one, or
is there a way to spawn another dogwood tree from an existing one?