Najas marina Linnaeus. Subgenus: Najas. Section: Najas. Holly-leaf Naiad. Phen: Jul-Oct. Hab: Brackish or calcareous waters. Dist: Scattered in ne. and nc. North America; FL; sw. United States, nw. United States (Freeman & Pfingsten 2021), Mexico, Central America, and South America; West Indies; Eurasia.

ID notes: The easiest of our naiads to recognize, Najas marina is distinctive in its irregularly and deeply serrate leaves and the spinose stem internodes and leaf midveins (but note that late-season leaves of Najas minor can become spinose and more deeply lobed).

Origin/Endemic status: Native

Taxonomy Comments: Najas marina has a broad distribution in the Northern Hemisphere, and was often subdivided into multiple species, subspecies, and/or varieties before a trend to lumping prevailed. Recent molecular studies show that multiple separate taxa, best accorded species rank, should indeed be recognized (Bräuchler 2015; Rüegg et al. 2017); as these studies have only been done in Europe, it remains unknown what taxa of "Najas marina" we have in the flora region, but likely not a single taxon and likely not Najas marina.

Synonymy ⓘ: = AqW, Bah, C, ETx1, F, FNA22, G, GrPl, Il, K1, K3, K4, Meso6, Mi, NY, Pa, SFla, Tx, WH3, Freeman & Pfingsten (2021); > Naias gracilis (Morong) Small – S, S13, orthographic variant; > Naias marina – S, S13, orthographic variant

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: OBL
• Eastern Mountains and Piedmont: OBL
• Great Plains: OBL
• Midwest: OBL
• Northcentral & Northeast: OBL

Heliophily ⓘ: 5