Plant id (with photo)
I'm wondering if anyone can identify this plant. It grows in patches in usually shady areas. It is a single stem with opposing leaves that grow in pairs; it grows to about 3 feet in height or so. In June it flowers with grayish purple flowers. In August it seeds with light green seedpods at the top of the plant.
This is a picture of the plant I took in early September:
Thanks for the help.