Marram Grass on the Polish Baltic Coast

What Marram Grass Is

Ammophila arenaria, commonly called marram grass, is a perennial grass native to the Atlantic coasts of Europe and northwest Africa. It grows in dense tussocks and is considered one of the most important dune-building plants in the temperate zone. Along Poland's Baltic coast, it is the dominant species of the foredune — the narrow ridge of sand closest to the shoreline.

The plant typically reaches between 60 and 120 centimetres in height and produces stiff, tightly rolled leaves that reduce water loss. Its rhizome system extends both horizontally and vertically, binding sand particles and preventing them from being redistributed by wind. When sand accumulates around the plant's base, it responds by growing upward — a characteristic that allows it to keep pace with an accreting dune rather than being buried.

Distribution Along the Polish Baltic Shore

Marram grass is present along the entire length of the Polish Baltic coast. It is especially abundant in areas where the beach is wide and sand supply is sufficient to maintain active foredune development. Notable concentrations occur around the Słowiński National Park near Łeba, along the Hel Peninsula, in the Bałtycki Coastal Park zone east of Gdańsk, and at sites near Dziwnów and Mielno further west.

At some locations the foredune belt is only a few metres wide; at others — particularly near Łeba, where the coast has been in a state of moderate net accretion — it extends to form a broad ridge several hundred metres deep. The stability of this ridge determines whether the grey dune and dune slack habitats behind it can develop.

How It Stabilises Sand

Marram grass works through a combination of physical and biological mechanisms:

• Aerodynamic roughness: the tussocks slow wind speed at the surface, reducing the threshold at which grains become airborne.
• Trapping: the leaf bases and stem bases catch saltating sand grains, encouraging deposition rather than transport.
• Root binding: the dense rhizome mat binds the upper sand layer and resists slumping during storms.
• Sand stimulation: unlike most plants, Ammophila arenaria grows more vigorously when partially buried, making it suited to the dynamic foredune environment.

The Foredune–Grey Dune Succession

Along the Polish coast, marram grass is part of a broader dune succession sequence. On the actively accreting foredune, it dominates almost exclusively. Behind it, where sand deposition is reduced, a transition zone develops. Here, Leymus arenarius (lyme grass) and Calamagrostis epigejos (wood small-reed) appear, gradually mixing with mosses and lichens. Further inland, the grey dune — characterised by low-growing vegetation including Corynephorus canescens and various lichen species — represents a later successional stage where the surface is more stable and nutrient levels are slightly higher.

Marram grass rarely survives into this later stage, as it requires sand movement to maintain its vigour. Its role is to create the conditions — dune accumulation, wind protection — under which later successional species can establish.

Threats and Conservation Status

Marram grass populations along the Polish coast face several pressures. Trampling by visitors to coastal beaches is among the most significant: even moderate foot traffic can break rhizomes, destroy tussock structure, and open gaps in vegetation cover that allow blow-outs to form. Blow-outs — circular or elongated depressions eroded into the dune by wind — can expand rapidly once initiated.

In several areas, particularly around Kołobrzeg and along the Hel Peninsula, marked pedestrian paths have been constructed specifically to channel movement away from the foredune. In the Słowiński National Park, visitor access to the foredune zone is restricted entirely in some areas.

Under Polish law, coastal dune habitats are classified as protected natural landscapes. The Ammophila arenaria community itself falls within the Habitats Directive Annex I habitat type 2120 (Shifting dunes along the shoreline with Ammophila arenaria — "white dunes"), which requires member states to maintain or restore favourable conservation status.

Restoration Planting

Where dune vegetation has been lost through erosion or trampling, marram grass has been used in restoration plantings along the Polish coast. The approach typically involves placing cut or bare-root marram tillers into sand at regular spacing, allowing the plant's natural sand-trapping capacity to begin rebuilding the dune profile. This technique has been applied at several sites managed by the Maritime Office in Słupsk (Urząd Morski w Słupsku) and by park authorities within Słowiński National Park.

Successful establishment depends on planting timing (spring or early autumn tends to produce better results), tiller source selection, and protection from immediate post-planting trampling. Where there is no adjacent natural population, tillers must be sourced from nurseries, and care is taken to use material of appropriate provenance to avoid introducing genetically mismatched stock.