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Posidonia oceanica
Also called Neptune Grass, Species code: Po
Posidonia oceanica is a seagrass (not a true grass) that forms large underwater meadows in the Mediterranean Sea and is found nowhere else. It is a marine plant that cannot be grown as a garden or houseplant; it needs clean, sunlit seawater and a stable seabed.
Posidonia oceanica, commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. The mapping of submerged seagrass meadows in the Mediterranean has recently benefited from advanced artificial intelligence techniques. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as "the olive of the sea" (l'oliva di mare). Balls of fibrous material from its foliage, known as egagropili or Neptune balls, wash up to nearby shorelines.
Posidonia has a very high carbon absorption capacity, being able to soak up 15 times more carbon dioxide every year than a similarly sized area of the Amazon rainforest.
This species is found only in the Mediterranean Sea, where it is in decline, occupying an area of about 3% of the basin. This corresponds to a surface area of about 38,000 km2 (15,000 sq mi). Posidonia grows best in clean waters, and its presence is a marker for lack of pollution. Local depth distribution can also be influenced by wave exposure, with hydrodynamic conditions contributing to the position of the upper meadow limit. The presence of Posidonia can be detected by the masses of decomposing leaves on beaches. Such plant material has been used for composting, but Italian laws prohibit the use of marine algae and plants for this purpose.
Text excerpted from the Wikipedia article Posidonia oceanica by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
