Eryngium aquaticum
Names: Eryngium aquaticum, Eryngium virginianum.
English: Button Snake-root; Rattlesnakemaster; Marsh rattlesnake master; Corn-snakeroot; Bitter snakeroot; Marsh eryngo.
Genus: 1 species.
Region: eastern North America.
Habitat: wet soils, bogs, marshes, ditches; tolerates saturated soils and periodic flooding.
Use: ornamental; often confused with Eryngium yuccifolium.
Botany
Biennial or perennial herb; up to 2 meters tall.
Stem: ribbed, erect; branches toward the top.
Leaves: alternate; lance-shaped, toothed on the edges; basal leaves up to 90 centimeters long and 9 cm wide.
Inflorescence: flower heads, with spiny, blue-tinged bracts
Flower: white to blue.