White Birds-In-A-Nest - Macbridea alba

White birds-in-a-nest (Macbridea alba) is endemic to the Apalachicola National Forest region of Florida - Liberty, Franklin, Gulf, and Washington Counties. In this localized area, it can be relatively common in scattered populations, but is listed as a state endangered species and by the federal government as a threatened species because there are so few of them.  This is a plant that occurs in seasonally wet, open habitats - wet prairies, flatwoods, and bogs.  The plants photographed above were found in an expansive bog dominated by yellow pitcher plants (Sarracenia flava), bit in elevations slightly higher than where the pitcher plants were thriving.
White birds-in-a-nest is a member of the mint family.  Few native mints are truly pure white, and this species stands out among the understory because of the way it glistens in the sun.  Its common name is easily understood by looking at the third photo above.  Flowers open atop the 18-inch stem in June and July. As they open, the winged blooms encircle the unopened white egg-shaped flower buds.
This is a perennial. I do not know if it persists overwinter as basal leaves or if it dies back to the ground; none of the published resources I have consulted describe this feature. Regardless, it is not a very interesting foliage plant. White-birds-in-a-nest reaches a mature height of 12-18 inches and rather succulent elliptical leaves line the stems, opposite each other, and with rough teeth at the outer margin.  The plants can be solitary or in small clusters.
White-birds-in-a-nest is threatened by modern forestry practices and by changing hydrology. It is not a good candidate for home horticulture because of its habitat specificity, but it is relatively well protected at this time in the State Forest where its well being is closely monitored.