Flora of the Southeastern United States

Panicum amarum Elliott var. amarulum (A.S. Hitchcock & Chase) P.G. Palmer. Common name: Southern Seabeach Grass. Phenology: Jul-Nov. Habitat: Coastal dunes and shores, sand-flats, and longleaf pine sandhills (by introduction). Distribution: NJ s. to FL, west to se. and s. TX and ne. Mexico (TAM); Mexico (Yucatan: CAM, ROO, YUC); West Indies; restricted to the Coastal Plain except for WV (where apparently introduced). Primarily a coastal plant, P. amarum var. amarulum has unfortunately been planted extensively in the Fall-line Sandhills of NC.

ID notes: Panicum amarum var. amarulum and P. amarum var. amarum are similar and sometimes confusable. They differ in general growth habit (long-rhizomatous with single stems in P. amarum var. amarum vs. short-rhizomatous with dense multistem tufts in P. amarum var. amarulum); foliage color (glaucous blue-green in var. amarum vs. green or yellowish green in var. amarulum); and panicle architecture (narrow, contracted, and spikelike in var. amarum vs. wider and more divergently many-branched in var. amarulum). Although the two sometimes co-occur in Coastal dune systems, var. amarulum is primarily a plant of secondary dunes and inland sands while var. amarum is most abundant on foredunes, upper beaches, and overwash flats (Virginia Botanical Associates 2023).

Origin/Endemic status: Native

Taxonomy Comments: Palmer (1975) reduced P. amarum and P. amarulum to infraspecific rank; their broadly overlapping distributions and suite of characters suggests that they are separate lineages. Ultimately, this taxon is not part of Panicum sensu stricto.

Synonymy ⓘ: = K4, Meso6, Pa, Va, Lelong (1986); = Panicum amarulum Hitchc. & Chase — Bah, C, F, G, HC, RAB, S, SFla, Tat, Tx, WV; = Panicum amarum Elliott ssp. amarulum (Hitchc. & Chase) Freckmann & Lelong — FlGr, FNA25, NE, NY, POWO, Zuloaga & Aliscioni (2023); < Panicum amarum Elliott — Mex. Basionym: Panicum amarulum Hitchc. & Chase 1910

Links to other floras: = Panicum amarum ssp. amarulum - FNA25

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: FAC (taxonomic split from wetland indicator species)
• Eastern Mountains and Piedmont: FACU (taxonomic split from wetland indicator species)
• Great Plains: FACU (taxonomic split from wetland indicator species)
• Northcentral & Northeast: FACU (taxonomic split from wetland indicator species)

Heliophily ⓘ: 8