Phemeranthus mengesii
| Phemeranthus mengesii | |
|---|---|
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| Phemeranthus mengesii in bloom | |
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| Succulent foliage of Phemeranthus mengesii | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Embryophytes |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Montiaceae |
| Genus: | Phemeranthus |
| Species: | P. mengesii |
| Binomial name | |
| Phemeranthus mengesii (W.Wolf) Kiger | |
| Synonyms | |
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Phemeranthus mengesii, commonly known as the large-flowered rock-pink, is a species of flowering plant in the family Montiaceae. It is a perennial herb endemic to the southeastern United States, where it grows in shallow soils on exposed granite, sandstone, and Altamaha Grit outcrops. These sites are often periodically wetted by seepage.[2][1]
Its range extends from western and central South Carolina through Georgia to northern Alabama and south-central Tennessee. Although rare across much of its range, it may be locally common at some Georgia rock outcrops.[2]
Description
Phemeranthus mengesii is a perennial herb adapted to exposed rock outcrops and very shallow soils. It produces narrow, fleshy leaves and a mostly leafless flowering stalk arising above the basal foliage.
The flowers are borne in an open, diffusely branched cyme on a scape-like stalk. The petals are pink to purple, and the flowers open during the afternoon.[3]
The species has substantially more stamens than most related southeastern rock-pinks. Its flowers generally contain several dozen stamens, a feature that helps distinguish it from species such as Phemeranthus teretifolius, Phemeranthus calycinus, and Phemeranthus piedmontanus.[3]
The seeds are smooth to slightly rough but are not conspicuously wrinkled. Flowering generally occurs from June through September.[2][3]
Taxonomy
The species was originally described by Wilhelm Wolf in 1920 as Talinum mengesii. Robert Kiger transferred it to the genus Phemeranthus in 2001.[4]
The current combination was published as:
- Phemeranthus mengesii (W.Wolf) Kiger, Novon 11(3): 320. 2001.[4]
The original name was published as:
- Talinum mengesii W.Wolf, American Midland Naturalist 6: 153. 1920.[4]
Modern classifications place the species in Montiaceae, although older treatments placed it in Portulacaceae.[2][4]
Taxonomic relationships
Phemeranthus mengesii belongs to section Phemeranthus.[2]
It is closely related to Phemeranthus parviflorus, a species centered in the midwestern United States but occurring disjunctly as far east as Alabama. The two species are considered likely parents of the more easterly allotetraploid Phemeranthus teretifolius.[2][1]
Both diploid and tetraploid populations of P. mengesii are known. Further research is needed to determine whether the tetraploid populations originated through genome duplication within the species or through hybridization with another taxon.[2]
Plants from North Carolina and Virginia that were formerly included within a broad concept of P. mengesii are now treated as the separate species Phemeranthus piedmontanus. Under the narrower modern circumscription, P. mengesii occurs only in Alabama, Georgia, South Carolina, and Tennessee.[1]
Similar species
Phemeranthus mengesii differs from Phemeranthus parviflorus in having many more stamens. P. parviflorus has relatively few stamens and its flowers open later in the afternoon.[3]
It differs from Phemeranthus teretifolius, Phemeranthus calycinus, Phemeranthus calcaricus, and Phemeranthus piedmontanus by its generally much greater number of stamens.[3]
It can also be distinguished from Phemeranthus rugospermus by its smooth or only slightly rough seeds. The seeds of P. rugospermus are conspicuously rough and wrinkled.[3]
Distribution
Phemeranthus mengesii is endemic to the southeastern United States. It occurs in Alabama, Georgia, South Carolina, and Tennessee.[1]
Its range includes rock outcrops of the Cumberland Plateau in Tennessee, northern Alabama, and northwestern Georgia. It also occurs in the Piedmont of Alabama, Georgia, and South Carolina, with disjunct populations extending into the Georgia Coastal Plain on outcrops of Altamaha Grit.[1][2]
Habitat and ecology
The species grows on exposed sandstone, granite, and Altamaha Grit outcrops. It is usually rooted in very shallow soil pockets that are periodically wetted by seepage.[2][1]
These habitats form part of open glade, barren, and woodland ecosystems. The species is strongly associated with sunny conditions.[2]
The shallow soils occupied by the plant may become seasonally wet but also dry rapidly. This creates an environment with limited competition from larger plants and favors species adapted to alternating wet and dry conditions.
Forest succession can reduce habitat suitability by shading rock outcrops and increasing woody cover. In some surrounding barrens and open woodlands, periodic fire may help preserve the open structure required by the species.[1]
Conservation
NatureServe classifies Phemeranthus mengesii as G3, or vulnerable, globally. It is also ranked N3 in the United States. State conservation ranks are S3 in Alabama and Georgia, S1 in South Carolina, and S2 in Tennessee. It has no status under the United States Endangered Species Act.[1]
The global assessment was reviewed on 12 December 2022 using NatureServe's conservation-rank calculator.[1]
NatureServe estimates that there are approximately 40 occurrences across the species' range, with a plausible range of between 21 and 80. Only a relatively small number of occurrences are considered to have good or excellent viability.[1]
The global population is estimated at several thousand plants. NatureServe reports an estimate of roughly 5,000 individuals based on records from Alabama and Tennessee, with additional plants occurring in Georgia and South Carolina.[1]
Threats include residential and commercial development, stone quarrying, recreational disturbance, off-highway vehicle use, camping, trash dumping, invasive plants, and forest succession. The invasive legume Lespedeza cuneata is specifically identified as a threat at some sites.[1]
The species is vulnerable to damage because it occupies thin soils and fragile rock-outcrop vegetation. Recreational traffic, collection, and soil disturbance can directly destroy plants or alter the small soil pockets in which they grow.[1]
NatureServe estimates a long-term decline and an ongoing shorter-term decline in populations and habitat quality. The principal causes include habitat destruction, recreational impacts, invasive plants, and increasing woody cover.[1]
Protected occurrences are known from William B. Bankhead National Forest and Little River Canyon National Preserve in Alabama, Obed Wild and Scenic River and Prentice Cooper State Forest in Tennessee, and several state-owned or privately protected conservation lands in Georgia.[1]
Recommended management includes restricting damaging recreation, preventing dumping and plant collection, controlling invasive species, and maintaining open rock-outcrop habitats. Selective forest thinning or prescribed burning may be needed in surrounding barrens and open woodlands where succession threatens occupied sites.[1]
References
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 "Phemeranthus mengesii". NatureServe Explorer. NatureServe. Retrieved 21 July 2026.
- 1 2 3 4 5 6 7 8 9 10 Weakley, Alan S.; Southeastern Flora Team (2026). "Phemeranthus mengesii". Flora of the Southeastern United States. Retrieved 21 July 2026.
- 1 2 3 4 5 6 Weakley, Alan S.; Southeastern Flora Team (2026). "Key to Phemeranthus". Flora of the Southeastern United States. Retrieved 21 July 2026.
- 1 2 3 4 "Phemeranthus mengesii (W.Wolf) Kiger". International Plant Names Index. Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Herbarium. Retrieved 21 July 2026.