Does a potted mint (nana) plant require trumos and maasros?
Yes it does. The reason is because it is eaten and used for its taste, and smell. One point though if you are taking maasros from an amount smaller than a perutah you will need a perutah charurah for the maaser sheini.
Mesechet Sheviis 7-1 see Rambam on that mishna that “Dandana” is “Nana”- hebrew for mint, also see Aruch that it is “mint”a”. See Divrie Shalom V’emes 1-16, and Divrei Binayahu 18-48.