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Dieren en planten

Water en land

Marram grass

size:

50 to 120 centimeters

color:

gray-green

blossoms:

June and July

reproduction:

seed, root stocks

life span:

perennial

  • Dut: Helm
  • Lat: Ammophila arenaria
  • Eng: Marram Grass
  • Fren: Oyat
  • Ger: Strandhafer, Helm
  • Dan: Sandhjælme
Marram grass, Ecomare

Marram grass

Marram grass is by far the most characteristic plant in the Dutch dunes. It is an important dune builder and coastguard. This tall, strong gray-green grass grows in tussocks along the entire Dutch dune coast. It makes long vertical root stocks which push deep down into the ground. The vertical root stocks also multiple horizontally, forming sturdy clumps underground and tussocks above ground. Marram grass has been planted on a large-scale specifically for building and stabilizing the dunes.

On Texel


, Sytske Dijksen, www.fotofitis.nl

In the 17th century, the islands Texel and Eierland were connected together with the help of marram grass. Willow branches were used to catch wind-blown sand in order to form a drift-dike on the sandbank lying between the two islands. As soon as it had grown enough for a freshwater bell to form, marram grass was planted to fortify the dike. 

  • Pioneer and survivor
    , Sytske Dijksen, www.fotofitis.nl

    Marram grass is a pioneer plant and one of the first species to grow in the dunes. Its major limitation is its intolerance to salt. Therefore, a freshwater reservoir must first form underground before the plant can start to grow. Sand couch starts the dune formation but as soon as the dune is around 1 meter tall, a freshwater reservoir forms and marram grass can grow. And grow it will: Marram grass can keep pace with 1 meter of sand drift per year!

    Not only is marram grass tolerant of sand drift, it actual strives from it. Sand drift encourages marram grass to develop more upper roots, which helps the plant to combat damaging insects. In areas where the vegetation is dense with other plants and therefore not much sand drift, marram grass becomes more susceptible to such insects and thereby less vital.

    Besides the harsh conditions along the beach ridge, marram grass can also survive well in hot dry dunes. The long narrow leaves are grooved on the inner side. The leaves are often rolled up, but when the weather is damp, they open up and absorb the moisture. By rolling up during warm weather, they retain the moisture and can survive long periods of drought. Of course, the long roots also help supply water.

    Strange enough, the clumps of root stocks can tolerate salt water. Erosion can dig out a clump of marram grass roots and waves can wash the clumps into the sea. Yet it is still possible for these clumps to take root elsewhere once they have been washed ashore. Naturally, it will have to be far from flooding saltwater and in touch with a freshwater source to grow.

  • Hydbrid marram
    Hybride marram (Foto Sytske Dijksen, www.fotofitis.nl), Sytske Dijksen, www.fotofitis.nl

    Hybrid marram looks a lot like marram grass but is an hybrid  of marram grass - wood small-reed. The plant doesn't usually produce seeds, but can multiple with its root stock. Unlike marram grass, hybrid marram roots spread more horizontally than vertically. The grass grows under the same conditions as marram grass and will intermingled with marram grass tussocks. It stabilizes dunes more quickly due to its horizontal roots. However, the deep roots of marram grass assure a sturdier dune. Rabbits won't eat hybrid marram as much as its parent plant.

  • Man-made coast

    The second half of the Middle Ages, the Flemish were the first to re-enforce their coast on a large scale with marram grass drift dikes. All of the weak areas in the dunes were tackled. They were so efficient that the Belgians still have a perfectly straight coastline.
    Later on, the Dutch living in Zeeland and Holland copied the Belgians. For example, the former islands of Callantsoog and Huisduinen were connected together in this manner. Up till 1970, there was a plan to attach Terschelling, Ameland, Schiermonnikoog and Rottumerplaat in this same way. The eastern part of the Wadden Sea could then be reclaimed. Growing appreciation for the wadden nature put an end to these plans.