Slender blue flag is a North American native species.
Identification: These irises are found in marshes,
in both fresh and salt water, and in coastal meadows. They are 12-36" (30-91 cm) high, with attractive purplish blue flowers atop long
2½-4" (6.3-10 cm) in size. Leaves are thin, long, and narrow, like large grass blades.
Wild Iris found in Newbury, Massachusetts (USA) 01951 on Newman Road. These flowers grow on an elevated spot on the salt marsh. An entire field of these irises can be found on Scotland Road, Newbury, MA 01951: cows graze here in an elevated salt marsh field. These are beardless iris, Iris Limniris (limniris is the sub-genus). My best guesses for species are Iris prismatica (slender blue iris) or Iris versicolor (northern/harlequin blue flag), but I haven’t done a proper tax’ing. The spot on the marsh where these can be found is lower than where Phragmites australis grows and higher than where the Distichlis spicata “wrack” grows. Photo and description by Lauren Noyes.
Iris prismatica on the Connecticut Botanical Society's Connecticut wildflowers site