What plant is that?

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Photo credits: © Francis R. Underwood 2017

The mystery plant this month is a perennial seen occasionally in wet habitats but also in dry fields or near old homesites.  It has opposite, entire leaves and stems which are slightly pubescent.  The flowers have 5 sepals and 5 petals.  Each petal however, is cut into 4 narrow lobes.  This plant grows 1-2 feet tall and the flowers are pink in color.  It blooms in late spring through early summer.

It’s. . .