information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Beaked tasselweed (Ruppia maritima)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.
Only coastal and marine records shown



The leaves are bright green, <1 mm wide, 20 -115 mm long, elliptical in cross section with pointed, slightly toothed tips. The leaves are held in membranous sheaths, 5 -22 mm in length at their base. A system of fine, slender rhizomes and fine roots holds the plants into the substratum. Flowers and fruits are borne on a characteristic coiled stalk (the peduncle), which may hold the flowers at the water surface or underwater. However, growth form is very variable, including long, tall plants in deep water, or tightly branched short plants in shallow, clear water. Dwarf forms have also been observed.

Recorded distribution in Britain and Ireland

Found all around the British coast wherever suitable habitat exists, as well as in brackish inland waters near Nantwich and Sanbach, Cheshire.

Global distribution

Ruppia maritima is a cosmopolitan species whose distribution is limited by the distribution of its habitat, between ca 69 deg N and ca 55 deg S.


Ruppia maritima grows in soft sediments in sheltered shallow coastal waters, from full salinity to nearly fresh water but mainly in brackish waters of lagoonal habitats, lochs, estuaries, creeks and pools in salt marshes, wetlands, ditches and lakes.

Depth range


Identifying features

  • Very slender stems, up to 0.4 m long, sparingly to richly branched.
  • Leaves, 0.35 -0.9mm wide, 20 -115 mm long, bright green with pointed (acute) slightly toothed tips.
  • Leaves ca 50 -210 times as long as wide.
  • Leave sheaths present, 5 -22 mm long.
  • Inflorescence borne on a slender, straight or tightly coiled peduncle, 12 -26mm in length but 0.5 -1.8 times as long as the longest carpel stalk.
  • Inflorescence of two flowers each with 3-5 carpels.
  • Seeds (duplets) pear-shaped, 2-2.8mm by 1.3-1.8mm, dark brown, with wine-red tubercles on surface.

Additional information

The taxonomy of Ruppia spp. is difficult and under revision. Ruppia maritima may be confused with Ruppia cirrhosa (syn. spiralis), which has dark green, wider (0.4 -1.4 mm) elongate leaves, with blunt tips, and whose flowers have a relatively longer peduncle (Preston, 1995). Dwarf forms of Ruppia maritima may be confused with the needle spike-rush Eleocharis acicularis.

Listed by

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Further information sources

Search on:


  1. Cronquist, A., 1988. The evolution and classification of flowering plants (2nd edn). New York: New York Botanical Garden.

  2. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  3. Kantrud, H.A., 1991. Wigeongrass (Ruppia maritima L.): a literature review. [On-line.], 2001-10-19

  4. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  5. Preston, C.D., 1995. Pondweeds of Great Britain and Ireland. London: Botanical Society of the British Isles. [B.S.B.I. Handbook no. 8.]

  6. Rodwell, J.S. (ed.), 2000. British plant communities, vol. 5, Maritime communities and vegetation of open habitats. Cambridge: Cambridge University Press.

  7. Verhoeven, J.T.A., 1979. The ecology of Ruppia-dominated communities in western Europe. I. Distribution of Ruppia representatives in relation to their autecology. Aquatic Botany, 6,197-268.

  8. Verhoeven, J.T.A., 1980a. The ecology of Ruppia-dominated communities in western Europe. II. Synecological classification. Structure and dynamics of the macroflora and macrofaunal communities. Aquatic Botany, 8, 1-85.

  9. Verhoeven, J.T.A., 1980b. The ecology of Ruppia-dominated communities in western Europe. III. Aspects of production, consumption and decomposition. Aquatic Botany, 8, 209-253.


This review can be cited as:

Tyler-Walters, H., 2001. Ruppia maritima Beaked tasselweed. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 20-08-2018]. Available from:

Last Updated: 19/10/2001