Ruellia caroliniensis is known commonly as wild petunia or Carolina wild petunia, despite the fact that it is not in Solanaceae (potato family, including petunias). It is actually a member of the Acanthaceae, or acanthus family, a primarily tropical plant family with a few representatives in temperate regions. Ruellia caroliniensis is one of those few, with its northernmost distribution reaching the northeast USA (and also reaching as far south as Texas and Florida).
The Lady Bird Johnson Wildflower Center has additional information on Ruellia caroliniensis.
Lastly, it’s likely that this will be the only BPotD entry this week, as I am traveling. Apologies!