Meet Your Neighbors

Marram Grass: Builder of Dunes

Photo: Jack Shouba

For millennia, the bright, tall green blades of marram grass lined most of the sandy shores of southern Lake Michigan. By 1981, extensive development along the Illinois coast had put the grass on the state endangered species list. But in recent years, the dune grass has been reappearing on Chicago’s shoreline, spicing the bather-filled beaches and volleyball matches with a welcome touch of duneland wildness.

An intrepid species of Lake Michigan beaches, marram grass, Ammophila breviligulata, is a perennial denizen of coastal sand from the Great Lakes to the Atlantic Coast. Mike Mycroft, a naturalist at Indiana Dunes State Park, calls it “the brashest of the plants” in the dunes. It grows closest to the water on the middle beach, where surf from brutal winter storms can wash it away. Wind and sand are also a constant danger in an environment that can bury entire stands of cottonwoods. But the threat of a sandy tomb only emboldens the grass, as burial stimulates further growth. Marram grass, also known as beach grass, is locally common at regional beachfront locations including Kenosha Dunes, Illinois Beach State Park, Indiana Dunes, and Warren Dunes. On Chicago’s lakefront, marram grass has found a home in small stretches of beach where human disturbances—particularly mechanical sand grooming—have been purposely limited.

Marram grass can grow to a height of three and a half feet. In summer, its flowering stalks appear as “beautiful golden spires,” in the words of Leslie Borns, volunteer steward at Montrose Beach Dunes. While it can reproduce by seed, marram grass spreads mostly by rhizomes, an underground lattice of roots that run parallel to the ground. In Dune Country: A Guide for Hikers and Naturalists, Glenda Daniel describes an exposed rhizome network as “looking like a mat of uncombed hair or stuffing from an old sofa.”

A piece of marram rhizome can blow or wash ashore, bury in the sand and generate a new plant. A single plant can produce more than 130 feet of rhizomes in just three years. Clumps of marram grass hold windblown grains of sand in place and begin to accumulate a mound of sand. Marram grass dunes can climb to between eight and ten feet tall. Along with its frequent pioneer companion, the cottonwood, marram grass is soon followed by sand cherry bushes, sand reed grass, and little bluestem.

“It’s exciting to see natural dunes develop and other plants appear,” said Susanne Masi, a scientist at Chicago Botanic Garden and coordinator of the rare-plant monitoring program Plants of Concern. “Marram grass provides a matrix for a whole system that begins to develop and grow.”

The Chicago Park District halted grooming of a section of Montrose Beach in the 1990s, and Borns first discovered marram grass there in 2000. The grass helped create several dune ridges and swales, and a panne—an extremely rare wetland ecosystem. Since then, the district has planted marram grass in other sections of beach, and it continues to reappear on its own.

“The reality is that the plants were here to some extent,” said Borns, “but because of coastal development, shoreline hardening, and beach management practices employing mechanized equipment, they couldn’t succeed.”

A cadre of volunteers and experts from Plants of Concern monitors marram grass, and they are hopeful for continued restoration. By encouraging this essential dune grass, they’re helping to roll out a rhizomatous welcome mat for the wilder beaches of Chicago.

— Robert Dolgan