Asarum rosei B.T.Sinn, 2017

Sinn, Brandon T., 2017, Asarum rosei (Aristolochiaceae), a new species from the Blue Ridge Escarpment of North Carolina, USA, Phytotaxa 296 (1), pp. 53-62 : 54-56

Asarum rosei B.T.Sinn , sp. nov. ( Fig. 1 )

Diagnosis:— Similar to A. heterophyllum Ashe , though notable for flowers with pale yellow-white (rarely green-white) sepal lobes covered in exclusively white multicellular trichomes which transition to entirely red within the calyx tube, and flowering period of late-May through June. Leaves are of similar shape to those of A. shuttleworthii Britten & Baker though not variegated, and with conspicuously undulating-crenulate margins.

Type:— UNITED STATES. North Carolina: Caldwell County, growing on the West (East facing) sloped road bank of Brown Mountain Beach Road (CR 1328) 0.5 km south of the junction with Harper’s Creek. Latitude 35 58.07N, longitude 081 45.49W, elevation 445 m. Growing along the roadside from just north of Harpers Creek south for approximately 1.2 km. 13 June 2016 R. Mark Rose collection # 2016-06-13 CA-A (Holotype: NY (FAA-fixed, ethanol-stored leaves and flower, and a living individual also accessioned into The New York Botanical Garden), isotypes distributed to: NCU, MO, US)).

Description:— Perennial herb, clumped growth habit with short rhizome. Petioles glabrous, over 18 cm in length. Leaf blades glabrous and entire, (7.4–) 8.2–11.2 cm long from base of lobe to the apex of the acute leaf tip and (6.8–) 8.5–11 cm wide, roundly- to oblong-cordate in shape, variegation not observed, the minutely revolute and entire leaf margins conspicuously undulate-crenulate; leaf lobes 2.1–3.7 cm long and 2.9–4.4 cm wide; calyx tube 1–1.5 cm long, (0.5) 0.9–1.2 cm wide at the orifice, with a pronounced protuberance distending the tube to (0.9) 1.1–1.5 cm in width at its broadest point which lies at approximately 2/3 of the distance from the base of the tube to the apex, the base white to pale yellow, sharply transitioning to a deep maroon above, trichomes villous with those inside the tube red and those of the sepal lobes entirely white; calyx reticulations composed of highly developed transverse and longitudinal lines of equal height, the height of the strongest of these reticulations surpasses the thickness of the calyx wall, and anastomosing to form deep irregular pits; sepal lobes (0.7) 1–1.2 cm long, weakly spreading, pale yellowgreen (rarely green-white), somewhat shorter or as long as they are wide at the base, with long-tomentose covering of uniformly white trichomes over the adaxial surface; stamens extrorse, thecae ~ 2 mm long and 0.5 mm wide, the broad filaments red and shorter than the styles, ~ 3 mm long tapering and surpassing the thecae by approximately 1 mm or less, the distal apex of the thecae slightly nearer to one another than proximally; ovary approximately 2/3 superior; styles gradually transitioning from white at the base to deep red at the apices of the highly developed, deeply cleft style extensions that surpass the ovoid, overhanging stigmas by> 2 mm; stigmas approximately 1 mm long and 0.5 mm wide. Fruit and seeds not seen.

Phenology:— Flowering late May–late June, fruits not seen by author.

Distribution:—Caldwell, Co., NC— The population occurs along a stretch of Brown Mountain Beach Road from just north of Harpers Creek south for approximately 0.8 of a mile to just above the K C Killian Camp property, and comprises approximately 600 individuals.

Habitat:— Acidic Cove Forest (Typic Subtype) per the Guide to the Natural Communities of North Carolina, Fourth Approximation ( Schafale, 2012).

Associates:— Rhododendron maximum , Kalmia latifolia , Tsuga canadensis , Betula alleghaniensis , Betula lenta , Liriodendron tulipifera , Leucothoe fontanesiana , Hydrangea arborescens , Euonymus americanus , Parthenocissus quinquefolia , Toxicodendron radicans , Aristolochia macrophylla , Xanthorhiza simplicissima , Mitchella repens , Asarum shuttleworthii , Polystichum acrostichoides , Parathelypteris noveboracensis , Actaea racemosa , Eutrochium sp. , and Laportea canadensis .

Conservation:— To-date, A. rosei is known from only a single locality. It is recommended that this species be evaluated for protection at the state level, at minimum.

Etymology:— Named for Mark Rose, a respected plant collector, horticulturalist, orchid breeder, and naturalist who discovered and documented the species that is here named in his honor. Mr. Rose ensured the recognition of this new species by way of his skilled observations, patient documentation, and curiosity for the natural world.

Other specimens examined:— No pre-existing specimens are known.

Figures

FIGURE 1.A) Habit of mature A. rosei individual at anthesis. B) Flowers of A. rosei showcasing entirely white trichomes covering sepal lobes. Photographs taken by Mark Rose.