Seagrass Zostera and Ruppia 

Seagrass is unique among flowering plants, in that all but one genus can live entirely immersed in seawater. More closely related to lilies and gingers than to true grasses, they grow in sediment on the sea floor, up to a depth of four metres. They have long narrow elongate leaves and a buried root-like structure, a rhizome. 


Seagrasses occupy a variety of coastal habitats, but typically occur in shallow, sheltered soft-bottomed marine coastlines and estuaries. Seagrass meadows may be monospecific or may consist of multi-species communities.  


  • Average length of leaves: 6-22 cm 
  • Lifespan: Life span of single leaves varies between two and six months over the year, depending on the period in which they first appear on the shoot 


Seagrass beds are a Priority Marine Feature, a UK Biodiversity Action Plan (BAP) habitat and an OSPAR (Oslo and Paris Convention) threatened and declining habitat. 


Seagrass meadows can be found around the coast of the UK, but as a habitat they are rare and declining.  Approximately, 90% have been lost, half of which over the past thirty years.

When to see

January to December 


  • There are four species of seagrass in the UK: two species of Tasselweeds (Ruppia maritima and Ruppia cirrhosa) and two Zostera species (Zostera marina and Zostera noltei), commonly known as eelgrass.  
  • Seagrass/algae meadows are rated the third most valuable ecosystem globally (on a per hectare basis), only preceded by estuaries and wetlands. 
  • Globally, seagrasses are as important as forests in storing carbon (on an area-basis); they can store carbon thirty-five times faster than rainforests. 


Common name


Species name

Zostera and Ruppia 

When to see in Scotland

January to December 

Where to see in Scotland

Beds of the dwarf eelgrass Zostera noltii are sparsely distributed around Scotland, but can be found in the Moray Firth, Firth of Tay, Shetland and the west coast and Western Isles on several Scottish Wildlife Trust snorkel trails.

Subtidal seagrass beds of the eelgrass Zostera marina are considered nationally scarce and found on the west coast of Scotland extending up to the Northern Isles. Tasselweed beds can be found on the west coast, the Outer Hebrides, Orkney, Shetland and, intertidally in the Cromarty Firth.

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