The deeply grooved leaf has a folded construction and it uncurls when mature so that the folds do not face the centre. The folds conserve water and withstand salt, as well as preventing excessive evaporation. Round vascular bundles are visible inside each fold, serving to transport food and water through the leaf.
These vascular bundles resemble a series of faces when viewed from above. Most commonly they are referred to as smiley faces, however this can be subjective as seen in other images they can appear as though they are screaming.
Spines on the surface discourage animals from eating the leaf. Marram grass is important in coastal ecology, since it is one of the most common grass species in Britain to stabilise sand dunes.