| Family | Scientific Name | Common Name | Habitat | Distribution | Image |
|---|---|---|---|---|---|
| Rubiaceae | Houstonia longifolia var. compacta | Eastern Longleaf Bluet | Dry rock outcrops and adjacent open woodlands, longleaf pine sandhills, dry sandy woodlands, dry roadbanks, glades and barrens. | Var. compacta is centered in the central Appalachians of VA, WV, e. KY, and se. OH, with extensions north to VT, west into n. IL, and south in the Piedmont and adjacent Coastal Plain to SC, GA, and Panhandle FL. |  |
| Rubiaceae | Houstonia longifolia var. glabra | Granite Dome Bluet | Seasonally and periodically wet soils of shallow soil mats and crevices of granitic domes. | Var. glabra is endemic to the granitic dome district centered around Highlands, NC, occurring in sw. NC, nw. SC, and ne. GA |  |
| Rubiaceae | Houstonia longifolia var. longifolia | Northern Longleaf Bluet | Dry sandy or rocky habitats. | New England and maritime Canada west to MN and SK, south to n. NJ, PA, n. IN, n. IL. |  |
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