A ride beside the artificial beaches along Highway 90 in coastal Mississippi provides a great view of the Mississippi Sound, but is often framed with what has become an extensive system of sand dunes, dressed in the ultimate dune plant – Sea Oats. Everything about this plant is designed to live in what is a harsh environment of sand and wind.
But it was not always this way. As far back as 30 years ago, Sea Oats were not present on our mainland beaches but relegated to the natural dune habitats of the barrier islands that define the southern boundary of the Mississippi Sound. The original mainland shoreline of the sound had few true beaches, edged instead with tidal marshes. The current beaches of the mainland are artificial constructs designed originally to protect the seawall that protects the highway. They are of course a main draw for locals and tourists.
But winds do blow across the sands of our mainland beaches and onto the roadway, that at times in the past built up in deep drifts that created dangerous driving conditions and required expensive and time-consuming removal. The construction of low-profile dunes and planting of Sea Oats over the past 20 years have helped alleviate this challenge by blocking wind-blown sands from getting to the roadway. If you look closely, in many locations, these dunes were built in two parallel rows, with gaps for navigating to the beach. These rows overlap each other to limit sand from blowing through the gaps. They have also added beauty to the scene.
The neat part of this story, however, is how well-adopted this plant is to the harsh environment of sand dunes. Sea Oats are long lived perennial grasses that naturally grow in well-drained coarse sands, despite living close to open water. Even with this grass’s association with water and salt, it tolerates only short periods of flooding and exposure to salt water, unlike tidal marsh plants that grow in nearby saturated soils.
In many ways, Sea Oats have attributes of desert plants that have extensive rhizome and root systems that seek the limited moisture in dunes, that are elevated above ground level and groundwater. These roots also stabilize the dunes and keep them largely in place. The above ground leaves and stems live best in full sunlight and face what for other plants would be harsh conditions. Sea Oats take it in stride, by design. They spread across dunes through their rhizomes that are stimulated to grow when disturbed by winds and shifting sands. It is as if the plants are trying to grow to hold onto the sands as much as possible.
What makes Sea Oats stand out are the dramatic and extensive seed heads that emerge and mature in late summer. The seed panicles consist of flattened spikelets that hang from the stems and wave in the breeze. When mature they are yellow to golden brown, contrasting with the green stems. They make great dry arrangements, but beware that because of their role in stabilizing dunes, they are illegal to harvest in many coastal states, including Mississippi.
For me, it is good enough to be able to see and appreciate how nicely Sea Oats dress up the artificial dunes on our artificial mainland beaches. But when the wind blows and the sands stay on the beaches, Sea Oats also deserve our gratitude.
Hope to see you in our great outdoors!