Last reviewed: May 2026
What marram grass does on bare sand
On a freshly deposited sand flat, wind removes loose grains continuously. Very few plants can establish under these conditions because sand burial kills most seedlings. Ammophila arenaria is a notable exception. When sand accumulates around its stems, the plant responds by producing new tillers and adventitious roots from buried nodes rather than being smothered. This upward growth response is the basis of its dune-building capacity.
The root system extends both horizontally and deep into the profile. Horizontal rhizomes — which can reach several metres in length — anchor surrounding sand while also spreading the plant's footprint. The dense leaf canopy reduces near-surface wind speed, causing more sand to drop and accumulate. The result is a self-reinforcing process: the plant traps sand, the dune grows, the plant responds by growing taller, trapping more sand.
Mechanism
Ammophila arenaria increases tiller production when the rate of sand burial reaches moderate levels. In experiments at Dutch and Danish coastal sites, plants subjected to moderate annual sand burial produced significantly more root biomass than plants on stable substrates. This stimulation effect disappears under extreme burial rates, where even marram grass cannot keep pace.
Foredune structure on the Polish coast
The Polish Baltic coastline between Świnoujście and the Hel Peninsula presents a largely continuous foredune ridge, interrupted by river mouths and inlets. This ridge varies in height from under one metre on recently formed embryonic dunes near Łeba to over ten metres on older consolidated foredunes further east. Ammophila arenaria dominates the seaward face and crest of this ridge along most of its length.
Behind the foredune crest, marram grass gives way to a transitional zone where other species begin to appear: sea sandwort (Honckenya peploides) in hollows, sea rocket (Cakile maritima) on the upper beach, and, on the more sheltered landward slope, Festuca rubra and Carex arenaria. This progression reflects decreasing sand mobility and increasing soil organic matter as distance from the beach increases.
At Słowiński National Park, the relationship between marram grass and moving sand is visible at landscape scale. The park's shifting dune complex — among the largest in Europe — demonstrates what happens when marram grass cover is lost: the dune advances inland unchecked at rates that have historically reached several metres per year. Where marram grass is intact, dune movement is negligible.
Root architecture and sand binding
Marram grass roots are coarse, fibrous, and resistant to desiccation. They can penetrate to depths of two metres or more in well-drained coastal sand, accessing moisture from below the summer dry layer. This deep root penetration anchors the dune against undermining during storm events, when waves may temporarily reach the foredune base and remove sand from the lower face.
The rhizome network between adjacent plants creates a matrix that distributes mechanical stress across a wider area than any single plant root system could manage. When storm waves cut into a foredune face, the exposed rhizome layer often prevents immediate collapse by holding the sand face intact long enough for conditions to stabilise.
Vegetation type
- EU Habitats Directive Annex I: Habitat 2120 — Shifting dunes along the shoreline with Ammophila arenaria
- This is a priority habitat under Directive 92/43/EEC
- Main associated species on the Polish coast: Cakile maritima, Honckenya peploides, Salsola kali, Elymus farctus
Limitations and decline
Despite its sand-binding effectiveness, marram grass is not invulnerable. Prolonged trampling from recreational use degrades the root network and kills tillers at the point of contact. On sections of the Polish coast with high beach visitor density — particularly around Gdańsk, Sopot, and Gdynia — foredune gaps created by pedestrian crossing points become erosion hotspots during storm events.
There is also evidence from northern European coastal systems that Ammophila arenaria populations senesce when sand supply decreases. Plants in stable, sandy environments without fresh sand input show reduced vigour and thinning stand density. This senescence has been documented in the Netherlands and Denmark and may also affect some sections of the Polish coast where longshore transport has been altered by harbour construction and coastal engineering.
Restoration practice
Where marram grass cover has been degraded, restoration generally involves transplanting plugs or tussocks of locally sourced Ammophila arenaria onto prepared sand surfaces. On the Polish coast, restoration projects have been carried out at several sites within and adjacent to Słowiński National Park, using material collected from donor stands within the same dune system. Sand fencing is often used alongside transplanting to reduce wind speed and encourage initial sand deposition around young transplants.
Access management — restricting pedestrian crossing to designated boardwalk routes — is consistently cited in the Polish coastal management literature as the most cost-effective long-term measure for maintaining marram grass cover on high-use beaches.
External references
For further reading on Ammophila arenaria ecology and dune stabilisation:
