Vascular Plants of North Carolina
Account for Marsh Eryngo - Eryngium aquaticum   L.
Members of Apiaceae:
Members of Eryngium with account distribution info or public map:
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Section 6 » Order Apiales » Family Apiaceae
DistributionThroughout the coastal and tidal zone, barely ranging west (inland) to Columbus County.

This is a nearly strictly coastal/tidal species, ranging from NJ south to southern FL and west to MS.
AbundanceUncommon, apparently seldom common anywhere. Sorrie did not see it in his natural areas inventory of Dare and Tyrrell counties (2012-14).
HabitatThis is mainly a species of tidal freshwater marshes, but it also occurs in brackish marshes, ditches, as well as wet ground along some blackwater rivers.
PhenologyBlooms from July to September, and fruits shortly after flowering.
IdentificationThis is a rather robust species, growing to 2.5-3 feet tall; it has some branches in the upper portions. The basal leaves are very long and narrow, often 10-12 inches long but barely 2 inches wide, with a long petiole; the margins are undulated or toothed. The stem leaves are much smaller and sessile; any leaf could have strong teeth, or be nearly entire, and a few stem leaves could be pinnately divided. The key is the beautiful inflorescence, a large umbel or cluster of umbels that are mostly flat-topped, at the top of the stem. Each umbellet is globose, with many light blue to medium blue flowers; the bracts beneath each umbellet, called a bractlet, is quite toothed to spiny. The recently split out E. ravenelii, limited in the state only to wet savannas over marl in Onslow and Pender counties, differs by 1) more rounded umbellets, whereas those in E. aquaticum are somewhat taller than wide; 2) fewer heads/umbellets than in E. aquaticum; and 3) the cusps of the bractlets are about equal in length, as opposed to the middle cusp of the bractlet being much longer than the lateral cusps in E. aquaticum. E. integrifolium also has sky-blue flowers, but its leaves are relatively short, and the blades of the basal and lower stem leaves are mainly no more than 3-4 inches long, with a length to width ratio about 1.5-3, as opposed to about 5 times longer than wide.
Taxonomic CommentsRAB (1968) and many references had E. ravenelii as a variety, named as E. aquaticum var. ravenelii; thus, the coastal marsh form was the nominate var. aquaticum.

Other Common Name(s)Water Snakeroot, Water Rattlesnake-master, Bitter Snakeroot, and others. There is simply no standard common name for this species.
State RankS3S4
Global RankG4
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B.A. SorrieSt. Marks NWR, FL, 1996. Scan from slide. Photo_non_NCPhoto_non_NC
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