Rhododendron smokianum Ralf Bauer & Albach, 2021

Albach, Dirk C. & Bauer, Ralf, 2021, Rhododendron smokianum, a New Species from the Great Smoky Mountains, Systematic Botany (Basel, Switzerland) 46 (1), pp. 122-129 : 126-127

Rhododendron smokianum Ralf Bauer & Albach , sp. nov.

TYPE: USA. Tennessee; Sevier Co.; Route 441 from Gatlinburg to Cherokee, below Newfound Gap in rocks beside the road at base of Anakeesta Ridge , ca. N 35.6225 W 83.4225; Hyatt A, grown from seed collected in 2015, flowered in cultivation in 2019 in the second author’ s garden, accession number 1269 (holotype: OLD 6300 ; isotypes: NY , US ).

Differs from R. minus in its much smaller and compact growth and in its smaller flowers having a very short or nonexistent tubular part of the corolla tube (0–2 mm long). Differs from R. chapmanii in its smaller flowers with a smaller opening and a very short or nonexistent tubular part of the corolla. Differs from R. carolinianum in its much later blooming time (end of June) and in its smaller flowers with a smaller opening and a very short or nonexistent tubular part of the corolla. The species differs from other species in two synapomorphic sites in the ITS sequence, but we refrain from calling them diagnostic in the absence of wider sampling of the species. Table 1 .

Shrubs, upright, richly branched, compact, (0.2–) 0.5–2(–2.5) m tall, usually considerably wider, no runners and not spreading by layers. Leaves evergreen, leathery, petiolate for 4–8 mm, lamina oval, apex with distinct, slightly downward-curving tip, margins smooth, base attenuate, 40–80 mm long, 10–30 mm wide, green on top, brown below, covered on upper surface with 3, on lower surface with 12–15 peltate scales (ca. 150 m m in diameter) per mm 2. Inflorescences terminal on annual shoots that are usually 1–10 cm long, appearing before flowering and usually almost fully developed during the flowering period; buds 8–15 mm long in winter, green to brown-scaly; peduncle 8–20 mm, usually 4–8 flowers per inflorescences. Flowers fragrance-less, corolla usually magenta or bright pink, more rarely pale pink or lavender pink, 20–25 mm long and 20–35 mm wide, narrow part of tube scarcely noticeable (0–2 mm in length), rest of tube (10–12 mm) expanding in a trumpet-like manner before 5 perianth segments can be differentiated, each segment 8–15 mm long and just as wide with strongly rounded tips, inside the corolla in the area of the upper perianth segment often some orange-brown to red spots; stamens 9–10, 7–25 mm long, white; pistil 12–20 mm long, red to whitish. Figures 4 , 5 .

Distribution and Conservation —The main distribution area is in Sevier Co., Tennessee, with only a few plants in Swain Co., North Carolina, at the Tennessee border ( Fig. 6 ). Closest populations of R. minus are ca. 37 km and those of R. carolinianum 42 km away. Rhododendron smokianum can be found in the whole area south of a line Mount Le Conte - The Boulevard - Mount Kephart from the highest peaks and ridges down to the valley of Walker Camp Prong between 1280 m and 2000 m above sea level. North from the Mount Le Conte summit it can be found along Rainbow Falls Trail on a ridge called Rocky Spur. Furthermore, there are few sites on Sugarland Mountain (Chimney Tops and along Sugarland Mountain Trail). The new species also grows along Route 441 going up from Walker Camp Prong to Newfound Gap. A single plant was observed along the Appalachian Trail between Newfound Gap and Mount Kephart, and an abundance of plants was encountered along the Appalachian Trail from Mount Kephart to Eagle Rocks. Despite its limited distribution area (19 km in eastwest direction and 7 km at the widest point in north-south direction), the new species is not endangered by collecting, agriculture, or settlement. As long as there are steep, anakeesta rocks, which cause repeated landslides, the species will be able to occupy new settlement areas. All habitats are located in the Great Smoky Mountains National Park. With the exception of the artificially (by road construction) created site on the road from Gatlinburg to Cherokee, all sites can only be reached by long and/or steep hikes.

Etymology —The epithet is derived from the distribution range, the Great Smoky Mountains.

Figures

FIG. 4. Rhododendron smokianum at the type locality at the base of Anakeesta Ridge. The white flowering shrub is Kalmia latifolia L.

FIG. 5. Flowers of R. smokianum from the population at Mt. Kephart, The Jumpoff.

FIG.6. Map of the known localities of R.smokianum based on personal observation of the second author.Elevations are given in meters. T 5 Type locality; map made with the TopoMap at gpsvisualizer.com.