Yes, I will occasionally sit in a beach chair, read a book, and sip on a malted beverage when visiting the Florida Panhandle, but what really attracts me to the Gulf Coast is the opportunity to wander in the Coastal Dune ecosystem and marvel at the uniqueness and natural artistry of this plant community.
To best understand the ecosystem it helps to break it down into the foredune, the one closest to the ocean, the secondary dunes behind it, and then the hind dune that transitions to forested areas.
On the foredune, at first glance we note the ubiquitous Sea Oats, as seen in the title photo – the anchors of the dunes, blowing in the breeze. They play the pivotal role, the pioneering plant, that develops a roothold. Then it functions as the dune builder, catching wind blown sand with their stems and leaf blades, and depositing it, granule after granule, at its base. It tolerates the accumulation of the sand, growing vertically, while still maintaining its deeply placed roots, which can extend 12 feet down.
The parent plant spreads by sending out rhizomes beneath the sand surface, from which other plants develop, clones of the parent, that act in concert to communally collect sand and enlarge the dune.
In summer Sea Oats sends up its flower, high above the remainder of the plant. Once pollination takes place the classic oat seedhead forms, and transitions from green to tan through the fall. They remain on display into the winter.
While a large number of seeds are produced, not all are viable. The germination rate is low due the harsh environment and the high number of seeds eaten by wildlife. The seed has to be buried at just the right depth to successfully germinate and grow – too deep and the plant will not have the energy reserves to persevere and penetrate to the surface, nor too shallow where it dries out or is eaten by a predator.
Once the Sea Oats are established other species begin to make a presence. There are other grasses, that while not as stately or famous, also doing their part to build the dune. Some of these do not even look like grasses at all:
Seashore Paspalum – again, not “grass-like” in structure, it inhabits the base of the foredune, growing toward the Gulf on the vegetated upper beach. A quick look on the internet tells me that it is offered as a commercial product because of its tolerance of salty environments where other lawn grasses struggle. Personally, I have seen it close to the water on golf courses along the Gulf and Intercoastal Waterway.
Seashore Dropseed – It is the wispy grass in the foreground in the first photo below, and enlarged on the second photo. It occurs on coasts world wide.
Marsh Fimbry – This sedge (a grass like plant) was found isolated, but amazingly structured, at the base of the foredune. The plant’s stems are solid and triangular, compared to grasses which are hollow and round. Perhaps it is these qualities that allow it to look so ornamental in its rather harsh environment.
Non-grass plants that help stabilize the dunes include:
Beach Morning Glory – these photos were taken in the winter when the plant is relatively dormant and not lush. Usually you would see very green leaves and white flowers. The second photo demonstrates the reach of single specimens with the vine spreading out over 25 feet or more.
Beach Pennywort – While vine-like in appearance, it is not truly a vine. It grows horizontally with spreading rhizomes below the surface. Its leaves can be eaten as a salad green and have a somewhat bitter celery taste.
On and amongst the secondary dunes are many of the plants of the foredune, but you also see flowering plants and low growing shrubs. These include:
Woody Goldenrod – not actually a Goldenrod but a member of the Aster family. It is classified as a sub-shrub, or “woody perennial”, which means it does not die back entirely to the ground at the end of the growing season and the next season’s new growth arises from buds on the semi-woody stems, close to the ground.
Skyblue Lupine – it only inhabits rather challenging environments and does not like the pampered life of being in a garden. It flowers in the spring and these photos were taken in April at Camp Helen State Park, Florida.
Seaside Gerardia – It has spike-like succulent leaves to avoid desiccation (water loss). It is native to much of the Gulf and Atlantic Coasts but “threatened” in some of these locales. It is an annual and each flower only lasts one day.
Seaside Goldenrod – compared to other Goldenrods, it has developed thick succulent leaves.
October Flower – the plant is non-descript until it sends off these racemes of flowers in October and November.
Coastal Plain Honeycombhead – named for the seed head that remains after it dries and the flower petals fall off. It looks like honeycomb.
Coastal Plain Goldenaster – is a biennial, germinating one year and flowering the next. The lower leaves dry out as the plant matures and is one of its identifying characteristic.
Florida Rosemary – really is not a team player when it comes to dune building as it is one of the more famous allelopathic plants known to botany, poisoning its neighboring plants with chemicals from its roots. These toxins interfere with microbes or nutrient availability. That was interesting to learn because we have often seen them in relative isolation. The effectiveness of this competitive quality can be seen in the third photo below. Some describe its scent as like Rosemary and others as a mint. Most authorities say it is not edible while others reference using it like a milder rosemary in cooking.
Seabeach Evening Primrose – native to the Gulf Coast and the Atlantic seaboard up to Maryland. It is both a nectar and larval host plant for many species of butterflies and moths.
As the dunes get further away from the seashore, larger shrubs species are noted. This begins the domain of Live Oak, Yapaun Holly, and Palmetto. Closer to the Gulf, they frequently look worse for wear, struggling to eke out a life in a difficult environment; high in salt and wind, and low in soil nutrients and fresh water. Specimens the size of a VW Beetle could be over 100 years old. The plants are frequently asymmetrical, and lean inland, away from the prevailing winds.
The final dune region is sometimes called the hind dune. Here the maritime forest arises with Live Oaks, Southern Magnolia and various pine species including Slash and Long Leaf Pines.
This is not a comprehensive list of all the plants that inhabit and contribute to the Coastal Dune Ecosystem but rather ones that I have become familiar with and have identified through my informal study. Here are some other interesting plants that I am still working to identify.
Every visit rewards me with something new.
The key, when considering the challenges that these dune plants face, is to understand that they were not evolutionarily selected to withstand human traffic. Walking on and amongst the dunes is one of the things that will cause these plants to die, with dune erosion and failure to follow. For that reason it is important for us coastal visitors to walk only in approved areas, which are usually limited to boardwalks that cross the dunes, or trails that weave between them. It is a small sacrifice to make for the ecological gem that the fragile Coastal Dune Ecosystem is.
And one last photograph that displays the peaceful chi that I feel when I observe nature at a dune.
Photos by Peggy Juengling Burns
Photos taken at Camp Helen State Park, Topsail Hill Preserve State Park, and Santa Rosa Island Dune Preserve.