Bartonia is a small genus of delicate annual and perennial flowering plants in the gentian family (Gentianaceae), placed within the tribe Gentianeae and subtribe Swertiinae. Members of the genus are known by the common name screwstems, a reference to the twisted, wiry stems characteristic of these plants. The genus is native to eastern North America.
Bartonia comprises three accepted species — Bartonia paniculata, Bartonia verna, and Bartonia virginica — all of which are small, inconspicuous herbs typically found in wet, acidic habitats such as bogs, pocosins, and wet pine savannas. The plants are notably slender, with scale-like or reduced leaves and small, four-petaled flowers.
The genus name Bartonia was also historically applied to plants now classified under the genus Mentzelia in the family Loasaceae, but modern taxonomy reserves the name exclusively for these gentians.
Etymology
The name Bartonia was applied to these plants historically; it was also formerly used for a separate group of plants (now Mentzelia, family Loasaceae), reflecting early taxonomic confusion. The common name "screwstems" refers to the characteristically twisted, wiry stems of plants in this genus.
Distribution
Bartonia is native to eastern North America. Its three species — B. paniculata, B. verna, and B. virginica — occur primarily in the eastern United States, typically in wet, acidic habitats including bogs, wet pine flatwoods, and pocosins.
Taxonomy Notes
Bartonia is placed in the family Gentianaceae, tribe Gentianeae, subtribe Swertiinae. Three species are accepted by Kew's Plants of the World Online: Bartonia paniculata (Michx.) Muhl., Bartonia verna (Michx.) Raf. ex Barton, and Bartonia virginica (L.) Britton, Sterns & Poggenb. The genus name was formerly also applied to plants in the Loasaceae family that are now classified under Mentzelia.
