The only garden I've been to in NC is the Vanderbilt Estate. It is amazing and beautiful, perfect for a date like that. (She'll love you forever...
However, that does not jive with what location you are talking about. Look up the Vanderbilt estate, and check that out. If nothing else, you could go there. Amazing really. Do the horse tour and a picnic, awesome.
If not that then, I did a search for you: See below, and read through it.
Good luck!