Irish moss, a common red algae in the Narragansett Bay area.
Irish moss, a common red algae in the Narragansett Bay area.
Courtesy: NOAA

Irish Moss (Chondrus crispus)

Alternate common name: Red Seaweed.
Appearance: Reddish brown seaweed with flattened blades that fork off into rounded tips. Grows 2 to 6 inches tall and 4 inches wide.
Habitat: Inlets, tide pools, and lower intertidal zone.
Seasonal appearance: All year.

Description

Irish moss is a red seaweed with flattened blades that fork off from a short stalk to form fingers with round, blunt tips. The blades taper towards disk-shaped holdfasts, which are actually root-like anchoring structures. Typically, the blades are flat and slender. Irish moss is usually deep purplish red, but may also be white, brown, or green. When washed ashore, it will bleach to white.

Life History and Growth

When found in shallow waters, Irish moss has blades that spread and take on a broader form. In deeper, subtidal zones, Irish moss blades are narrower. It generally grows between 2 to 6 inches high and 4 inches wide. Each blade is flat and rubbery with crimped edges. Irish moss usually grows in clumps. It can withstand extremely cold water temperatures and can survive freezing during the winter months.

Special Notes


Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.