Why are marshes dominated by grasses, sedges, reeds, and rushes?

Marshes are wetland ecosystems characterized by poorly drained mineral soils and a steady supply of water, which creates a waterlogged environment. This specific habitat is dominated by grasses, sedges, reeds, and rushes because these plants are uniquely suited to survive in such conditions.12

In many cases, these plants are halophytic, meaning they have evolved specific adaptations to thrive in saline habitats, such as those found in salt marshes. Furthermore, the fibrous root systems of these grasses play a functional role in the ecosystem by binding mud together, which helps stabilize the soil and encourages the further development of the marsh.21

While marshes are often found at the mouths of rivers where sediment-rich water creates poorly drained land, the combination of constant water supply and waterlogged soil limits the number of plant species that can survive compared to well-watered but non-waterlogged land. Consequently, these specialized, grasslike plants become the dominant vegetation.1