Cuphea viscosissima

Cuphea viscosissima, also known as blue waxweed, clammy cuphea or (ambiguously) as "tarweed", is an herbaceous plant in the loosestrife family. It native to the eastern United States, where it is most often found in open, rocky calcareous areas. It is the most common and widespread "Cuphea" in the U.S.
This species is notable for its sticky stems. It produces a purple-red flower in late summer.
This species is morphological similar to "Cuphea lanceolata", which is found in Mexico. It can be distinguished from "Cuphea lanceolata" by its smaller flower.