Along the coast of Maine, saltmarsh plant communities are abundant and important. Studies show that saltmarshes can sequester carbon up to 10 times faster than forests! The broad umbrella of saltmarshes contain a gradient of plant communities that feature different characteristics based on salinity, easily distinguished by distance from the coast.
Salt-hay Saltmarshes form in estuaries or inland areas behind dunes or barrier islands. This community spreads far beyond the main channel of water, and only floods when tides are above average. Water will collect in salt pannes, unable to drain until it evaporates. The soil is peat and reaches down several feet. Mixed Saltmarshes are smaller plant communities that exist in pockets and coves along shoreline and estuaries. Deeper in the estuary where saltwater mixes with freshwater, Brackish Tidal Marshes take over. Here, the soil is mud rather than peat.
Closer to the coast, obligate saltwater species dominate. In Salt-hay Saltmarshes, species occur in bands matching up with tidal inundation zones. The meadow is filled with Cordgrasses and Saltmarsh Rush, with some Sea Lavender and Seaside Goldenrod at the fringes of the marsh. There are almost no shrubs.
There is a similar species composition in Mixed Saltmarshes, except species occur in patches instead of bands. Here, you will find rushes such as Chair-maker’s Rush, grasses like Sweetgrass, New England Aster, Saltmarsh Sedge, and Narrow-leaved Cattail. As the estuary moves into a Brackish Tidal Marsh, freshwater and brackish species occur in bands according to tidal exposure. There are no more Saltmarsh Cordgrasses, but every species is tolerant of salt in some capacity. In the lower elevation mudflats, there are rosette-forming herbs such as Tidal Arrowhead. There are plenty of rushes in the mid-elevation areas. Higher up where the tide cannot reach, there is muddy gravel or rock where Sweetgale and Poison Ivy grow.
Saltmarshes provide crucial habitat for a number of species. The rushes and grasses provide nesting habitat for rare sparrows such as Nelson’s Sharp-tailed Sparrow, Seaside Sparrow, and Saltmarsh Sharp-tailed Sparrow. There is also excellent foraging for wading birds and shorebirds, including the rare Least Tern, Great Egret, and Glossy Ibis. The Big Bluet, a rare damselfly, is adapted to salt water and relies on saltmarsh habitats. In brackish areas, Freshwater Cordgrass is the host plant for the Spartina Borer Moth.
Here are three important saltmarsh plant species:
Saltmarsh Rush
Like the name suggests, this rush is commonly found in saltmarsh plant communities. It prefers salty, waterlogged soils, but cannot tolerate much flooding. Saltmarsh Rush grows 1-3 feet tall, with long stems and long, thin leaves that alternate along the stems. It has rhizomes that grow dense and long-forming clonal populations by reaching out to any unoccupied space. Greenish-brown, round flowers emerge in late spring and are pollinated by wind. The fruit is an egg-shaped capsule, green when unripe and darkening into a characteristic dark brown when ripe. The seed pod splits in three to release small seeds that are dispersed by wind or water.
Because of the deep rhizomes, Saltmarsh Rush makes an excellent plant for erosion control. It is also currently being studied for phytoremediation—the use of plants to clean up and absorb pollutants from the environment. This rush is able to store toxic heavy metals such as cadmium and lead in its roots. Saltmarsh Rush is also used by indigenous peoples to make baskets, mats, and ropes.
Wildlife also benefits from this rush that constitutes much of the biomass of saltmarsh plant communities. The dense foliage makes great habitat for shorebirds, and the seeds provide food for waterfowl and shorebirds. Rabbits are also known to eat the flowers!
Seaside Goldenrod
This goldenrod is well-adapted for salty and sunny areas such as saltmarshes! It can reach up to 6 feet tall under optimal conditions. Unlike most goldenrods, the leaves are toothless, hairless, and are relatively thick with a rubbery texture. The long-lasting, dense, yellow flowers bloom in a plume from August to September. These yellow flowers become fluffy white seed heads that are dispersed by wind. Seaside Goldenrod doesn’t spread through rhizomes like other goldenrods—instead, it relies entirely on this seed dispersal.
This goldenrod is great for erosion control, especially in salty coastal areas. Goldenrods are also often used as a diuretic for urinary health, helping relieve symptoms of UTIs and kidney stones. The leaves and flowers of goldenrod can be made into a tea that relieves allergy symptoms, and the flowers make a beautiful yellow dye!
Goldenrods are also important for many various insects. The genus Solidago is known for hosting the largest number of caterpillar species, totalling 124 species. Goldenrods also support insect galls and provide habitat for overwintering insects, such as bees and predatory wasp larvae. While all late-season goldenrod blooms provide critical pollinator value, Seaside Goldenrod is perfectly matched with Monarch migration. The bloom time and location along the coast create a highway of yellow flowers for Monarchs to move south.
Sweetgale
Sweetgale occurs in the upper reaches of Brackish Tidal Marshes, along with other bogs and wetlands in the wild. This shrub can grow up to 6 feet tall, and it forms clonal colonies from root suckers. As the name suggests, this shrub has sweet and fragrant foliage, especially when the leaves and fruits are crushed. The leaves are oblanceolate, meaning they are thin leaves that widen towards the tip. The flowers are round and spiky, with colors ranging from yellow to green to brown. The fruit is small and looks like a golden-brown pinecone.
There are many historical uses of Sweetgale. The dried leaves and fruits can be made into a spice or a tea. In Europe, it was used as part of the flavor mixture in beer until the 16th century when hops fully took over. The aromatic leaves work as an insect repellent, and the waxy fruits can be made into candles. In the United Kingdom, sprigs of Sweetgale were traditionally part of royal wedding bouquets.
Sweetgale also adds a wealth of wildlife value to its ecosystem. Firstly, it partners with nitrogen-fixing bacteria that improves the quality of the soil. Muskrats and deer browse the foliage, and birds eat the fruits. The branches provide cover and nesting for sparrows and Ring-necked Ducks. Beavers will also use these sticks and branches to construct their dams.
To learn more about saltmarsh plant communities, check out our upcoming webinar and plant walk:
Salt Marshes: Maine’s Dynamic Coastal Communities – Webinar, September 22, 5-6 pm
Where land and sea meet, one of Maine’s most productive and resilient ecosystems thrives. Join Maine Audubon’s Native Plants Program for an exploration of Maine salt marshes and the remarkable plant communities that have adapted to life between the tides. These coastal habitats provide critical benefits, from buffering storm surge and improving water quality to supporting fish, birds, pollinators, and countless other species.
Participants will learn how salt marshes are structured, the environmental forces that shape them, and the native plants that define different zones across the landscape. We’ll explore the ecological relationships between marsh plants and wildlife, examine the role of salt marshes in coastal resilience, and discuss how these communities are responding to sea-level rise and other environmental changes.
Webinar on September 22, 5-6 pm: Sign up here >
Natural Communities Visit – September 23, 5:30-6:30 pm
Following the Natural Communities webinar on September 22, explore Scarborough Marsh during shorebird migration to learn how these unique communities support wildlife in Maine and beyond. Our naturalist will identify plants and animals that shape and rely on these tidal wetlands.
Visit on September 23, 5:30-6:30 pm: Sign up here >
