Vascular Plants of North Carolina
Account for Rose's Heartleaf - Hexastylis rosei   (B.T. Sinn) Weakley & D.B. Poind.
Members of Aristolochiaceae:
Members of Hexastylis with account distribution info or public map:
Google Images
Section 4 » Family Aristolochiaceae
Author(B.T. Sinn) Weakley & D.B. Poind.
DistributionKnown only from two very small areas of Caldwell County. This taxon was described as a species by B.T. Sinn in 2017 but named as Asarum rosei. However, placing it in Asarum has upset a number of taxonomists, as they feel that this should be placed in Hexastylis with the other evergreen species and not in the deciduous-leaved Asarum. Therefore, Weakley and Poindexter (2020) altered the name to Hexastylis rosei (B.T. Sinn) Weakley & D.B. Poind.

This species is endemic to Caldwell County, NC, as far as known. It was discovered only in 1998, by Mark Rose.
AbundanceAlthough it grows in dense patches in two small areas of the county, essentially no other populations have yet been found, though it seems likely that a few additional others must exist nearby. NCNHP has given it a State Rank of S1, and a Significantly Rare status. As the species has been named, even if the name is a bit unsettled, it is hoped that it will be afforded legal state protection as Endangered very soon. NatureServe gives it a Global Rank of G1, though listing it as Asarum rosei.
HabitatThis species occurs in acidic soil of slopes under or very near Rosebay Rhododendron (Rhododendron maximum). Most plants are actually on a sunlit exposed roadbank, where often mowed, but a second one (reported in 2020) is on a steep slope in a more undisturbed setting, close to rhododendrons, Galax (Galax urceolata), and a few other species.
PhenologyBlooms mainly in June, and fruits shortly after flowering.
IdentificationThis species is a heartleaf that visually seems to have crossed with Galax (Galax aphylla)! Unlike the other round-leaved heartleafs, which have entire leaves, the leaves of this species are somewhat scalloped and can strongly resemble those of Galax; but this latter species has clearly serrated leaf margins (and not scalloped). The heartleaf has a very deep basal sinus, even more so than in other Hexastylis species. Galax leaves, though evergreen, are quite thin and flexible, whereas heartleaf species have a rather thick leaf. Also, a Galax leaf shows 6 or more pale veins radiating from the base of the leaf, with no vein being the obvious midrib one; the leaf of H. rosei has a pale vein from the base running along the midrib, with a few pale veins coming off this midrib vein (see first photo below). The leaves are about 4 inches across and wide (larger than other heartleafs), unmottled bright to dark green, and with a quite long petiole up to 7-8 inches long; several leaves grow in a clump. The flowers are striking cream to pale-yellow on the lobes (on the inside), easily visible to the observer as these long lobes are spreading horizontally. Each spread flower is roughly 1 inch across, heavily covered in white hairs on the inside of the lobes and calyx tube. A cluster of flowers in full bloom is quite noticeable at some distance. You should check Google images for more photos of the leaves and flowers of this very unusual species. Also, excellent photos are included in a paper announcing the second population: Phytoneuron 2021-4.
Taxonomic CommentsThe hesitancy for this odd taxon to be given a name was understandable, as it was so different from all others that perhaps it was an odd mutant. And with the frequent mowing of the plants on the roadbank, perhaps mowing had affected the usual growth of the species under deep shade conditions. However, with the discovery of a second population, doubts concerning its validity as a good species are vanishing.

Other Common Name(s)Another common name has been given by a few entities, but that name is not used here as it is a geographical one. For protection purposes, this website uses the name given by the NCNHP and Weakley (2018) after its discoverer -- Rose's Heartleaf.
State RankS1
Global RankG1
State StatusSR-L
US Status
USACE-agcp
USACE-emp
County Map - click on a county to view source of record.
Photo Gallery
photographercommentsphoto_linkcountyobsType
Jesse ShanerLeaves, along with Galax for comparison. CaldwellPhoto_natural
Jesse ShanerFlower. Note uniform color of hairs and tepal lobe interior. CaldwellPhoto_natural
Select a source
AllHerbaria
Individual
Literature
Select an occurrence type
AllCollection_naturalLiterature_naturalPhoto_natural