Mazus pumilus (Japanese Mazus) looks like a cultivated plant that just crawled out of a neighborhood garden. But in fact it is an introduced species that has become naturalized throughout the eastern United States. Originating in East Asia, Mazus pumilus is a member of the lopseed family (Phrymaceae) with opposite, short, paddle-like leaves and very beautiful small flowers. The size of the flowers can be compared to the neighboring clover leaves in the first photo below. It is an annual that has the ability to pop up suddenly in a new location, as it did at the Shinleaf State Recreation Area of Falls Lake recently. In its new location, it may either take hold and spread or disappear the following year. Seeds are initially disseminated by splashes of rain, but may also later be eaten by herbivores and spread in their droppings. In the case of the Falls Lake area, the herbivores would be the ubiquitous White-tailed Deer.
Thanks to Hugh Nourse for identifying the plant after he discovered it growing in his driveway.