What is this
I bought this plant a couple months ago. It didn't have a name on the tag but said it was tropical.
Montgomery County Tennessee tropical plants
It looks like a firebush (Hamelia patens), a member of the coffee (Rubiaceae) family from Central America. Along the Gulf Coast, it tends to make an herbaceous perennial, but would probably be an annual in Tennessee. It could also be kept in a large pot and brought indoors for the winter, if you'd want to keep it longer. Plants prefer well-drained soil, full sun, and love the heat. They are also used to attract butterflies and hummingbirds.
Hope this helps!