Whiteweed (Sertularia cupressina)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



This colonial hydroid is notable for its white or silvery colour. Known commonly as white weed, it resembles a plant with both branches and a stem. Colonies are branched, bushy, and usually up to 30-35 cm in length but can reach 50 cm. In general, there are only two branches per internode with the upper part of the stem slightly spiralled. The hydrothecae (cup-shaped extensions) alternate and are tubular with two teeth (slightly uneven in length). The small polyps on the branches are able to retract into the bottle-shaped openings of the cups.

Recorded distribution in Britain and Ireland

Recorded throughout British and Irish waters

Global distribution

Widespread in the North Atlantic including North America


Sertularia cupressina is found in a range of habitats from estuaries to the open coast attaching to hard substrata such as scallop shells, characteristically in sandy areas. They are also found on oyster-beds. 

Depth range

1 - 100 m

Identifying features

  • Colonies are erect and bushy
  • Younger colonies are pinnate.
  • Main stems straight.
  • Hydrothecae alternate and are tubular with two teeth (slightly uneven in length).
  • White to silver in colour
  • Up to 50 cm in length, usually 30-35 cm. 

Additional information

Sertularia cupressina is often confused with Sertularia argentea, and numerous authors consider them to be conspecific. Currently, the two names are considered valid, but owing to the taxonomic uncertainty, results of scientific studies may include/exclude either species (see Cornelius, 1979).  Whiteweed is commonly sold for decoration in houses. Colonies naturally age and thereby detached from the substratum every August. Sertularia cupressina can, however, regenerate its entire body.

Listed by

- none -


  1. Berghahn, R. & Offermann, U. 1999. Laboratory investigations on larval development, motility and settlement of white weed (Sertularia cupressina L.) - in view of its assumed decrease in the Wadden Sea. Hydrobiogia, 392(2), 233–239.

  2. Cornelius, P.F.S. 1979. A revision of the species of Sertulariidae (Coelenterata: Hydroida) recorded from Britain and nearby seas. Bulletin of the British Museum (Natural History) Zoology

  3. Cornelius, P.F.S., 1995b. North-west European thecate hydroids and their medusae. Part 2. Sertulariidae to Campanulariidae. Shrewsbury: Field Studies Council. [Synopses of the British Fauna no. 50]

  4. Hancock, D.A. Drinnan, R.E. Harris, W.N. 1956. Notes on the biology of Sertularia argentea L. Journal of the Marine Biological Association of the United Kingdom, 35, 307-325. DOI https://doi.org/10.1017/S0025315400010158

  5. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  6. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  7. Schmidt, G.H. & Warner, G.F., 1991. The settlement and growth of Sertularia cupressina (Hydrozoa, Sertulariidae) in Langstone Harbour, Hampshire, UK. Hydrobiologia, 216-217, 215-219. 

  8. Wagler, H., Berghahn, R. & Vorberg, R., 2009. The fishery for whiteweed, Sertularia cupressina (Cnidaria, Hydrozoa), in the Wadden Sea, Germany: history and anthropogenic effects. ICES Journal of Marine Science: Journal du Conseil, fsp201.


  1. Bristol Regional Environmental Records Centre, 2017. BRERC species records recorded over 15 years ago. Occurrence dataset: https://doi.org/10.15468/h1ln5p accessed via GBIF.org on 2018-09-25.

  2. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset https://www.nmni.com/CEDaR/CEDaR-Centre-for-Environmental-Data-and-Recording.aspx accessed via NBNAtlas.org on 2018-09-25.

  3. Environmental Records Information Centre North East, 2018. ERIC NE Combined dataset to 2017. Occurrence dataset: http://www.ericnortheast.org.ukl accessed via NBNAtlas.org on 2018-09-38

  4. Kent Wildlife Trust, 2018. Kent Wildlife Trust Shoresearch Intertidal Survey 2004 onwards. Occurrence dataset: https://www.kentwildlifetrust.org.uk/ accessed via NBNAtlas.org on 2018-10-01.

  5. Manx Biological Recording Partnership, 2018. Isle of Man historical wildlife records 1990 to 1994. Occurrence dataset:https://doi.org/10.15468/aru16v accessed via GBIF.org on 2018-10-01.

  6. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  7. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-04-21

  8. South East Wales Biodiversity Records Centre, 2018. SEWBReC Marine and other Aquatic Invertebrates (South East Wales). Occurrence dataset:https://doi.org/10.15468/zxy1n6 accessed via GBIF.org on 2018-10-02.

  9. South East Wales Biodiversity Records Centre, 2018. Dr Mary Gillham Archive Project. Occurance dataset: http://www.sewbrec.org.uk/ accessed via NBNAtlas.org on 2018-10-02


This review can be cited as:

Hosie, A & Gibson-Hall, E 2018. Sertularia cupressina Whiteweed. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-04-2024]. Available from: https://www.marlin.ac.uk/species/detail/2219

Last Updated: 02/08/2018