Eryngium ludovicianum

Eryngium ludovicianum is a perennial herb characterized by slender, erect stems and narrow, linear-lanceolate leaves. Leaves are typically 3–8 mm wide and bear relatively sparse marginal teeth. In the 2024 revision of the Eryngium integrifolium species complex, the species was distinguished by its combination of narrow leaves, low density of marginal teeth, and overall gracile habit, separating it from morphologically similar taxa. It is most similar to Eryngium lanceolatum, but differs in having narrower leaves and fewer teeth per unit length of the leaf margin. ==Taxonomy==

The species was first described by Thomas Morong in 1887. It was later treated as a variety of Eryngium integrifolium and, less commonly, associated with Eryngium virgatum. A comprehensive revision of the Eryngium integrifolium species complex in 2024 reinstated Eryngium ludovicianum as a distinct species based on consistent morphological differentiation and geographic segregation. This revision recognized several closely related species in the complex, including Eryngium lanceolatum, Eryngium mississippiense, and Eryngium altamaha. ==Distribution and habitat==

Eryngium ludovicianum is endemic to the West Gulf Coastal Plain, occurring in eastern Texas and Louisiana. The species has a more southerly istribution than Eryngium lanceolatum, which occurs primarily farther north and west. ==Ecology==

Eryngium ludovicianum is associated with wet savanna and seepage habitats within longleaf pine systems. These environments are typically maintained by periodic fire and characterized by seasonally saturated, acidic soils. Flowering occurs from August to October. ==Identification==

Within the Eryngium integrifolium species complex, Eryngium ludovicianum can be distinguished by: • Narrow leaves (typically 3–8 mm wide) • Sparse marginal teeth (fewer per centimeter than related species) • Occurrence in southern Gulf Coastal Plain seepage habitats It differs from: • Eryngium lanceolatum — broader leaves, more densely toothed margins • Eryngium mississippiense — more robust habit and different geographic range • Eryngium altamaha — restricted to the Altamaha River region of Georgia ==See also==