Discover the fascinating journey of cordgrass and the origin of those brown sticks dotting our shores

Sticks on the beach? It’s marsh grass!

Story by Amber Kuehn

Sporobolus alterniflorus, commonly known as smooth cordgrass or marsh grass, is a perennial plant that marks the changing seasons in the Lowcountry. Its blades shift from emerald green in summer to amber in fall, eventually turning brown in winter. As marsh grass dies back, the brown reeds break away, carried off by the rising tide to make way for new growth — an essential cycle that sustains the marsh ecosystem.

The moon’s influence 

When the tide flows inland after slack tide, offshore wrack accumulates in front of Hilton Head beaches. The surf tumbles these bundles before depositing them at the highest tide mark. Wrack formations on the beach align parallel to the shoreline, forming distinct north-south lines. The precise location of these deposits depends on the phase of the moon:

Spring tide: A full moon event deposits wrack closer to the dunes.

King tide: When the gravitational pull of the sun and moon align, marsh grass from the farthest reaches of the wetland is swept to shore, creating larger wrack deposits even closer to the dunes.

What is wrack? 

The ebbing tide and coastal winds transport large bundles of dead reeds out of Lowcountry waterways, past boats in Calibogue Sound and, eventually into the ocean. These floating reeds, known as wrack, begin to decompose. Up close, wrack appears fuzzy with detritus — tiny bits of decayed plant matter that serve as a food source for small marine organisms.

More than just beach debris

At times, thick accumulations of wrack form small natural barriers along the beach. While some may see this as debris, wrack plays a crucial role in dune formation. The spaces between reeds trap windblown sand, laying the foundation for new dunes. Over time, layers of sand cover the wrack, and nutrients from the decaying reeds nourish sea oats and other vegetation. These plants take root, stabilizing the dunes and reducing erosion.

A man-made solution 

To counteract the impact of foot traffic, the Town installs sand fencing to trap sand and facilitate dune growth. These fences are strategically placed in a “V” shape for two key reasons:

1. To protect sea turtles: Gaps in the fencing allow turtles to exit safely after nesting. If a turtle encounters the fence, the angled design guides her toward the water.

2. To enhance sand accumulation: The “V” shape increases sand capture at its angle, helping dunes form more efficiently.

As soon as a noticeable mound develops, vegetation is planted to reinforce dune stability.

Nature’s coastal defenders 

Strong dunes provide critical habitat for wildlife, including nesting endangered loggerhead sea turtles and ghost crabs that burrow in the sand. Dunes serve as the first line of defense for Hilton Head’s barrier island during storms. Unfortunately, natural dune formation is hindered by human activity. Hilton Head Island, often named “America’s Favorite Island,” welcomes about 3 million visitors annually. 

Protecting the dunes 

Signs remind beachgoers to stay off the dunes, as even a single footpath can disrupt this fragile ecosystem. It is illegal to remove or cut dune vegetation, and maintaining these areas is essential for Hilton Head’s long-term coastal resilience.

Now that you know these fences are not barriers to dunes but rather tools to build them, please keep personal belongings like bikes, chairs and towels away from them. Being a good steward of the beach reflects Hilton Head Island’s commitment to protecting natural resources and ensuring environmental sustainability.