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vert bar Lagarosiphon major
Last updated 7th February 2010

Occasional in ponds and lakes, but likely to become more common. Most records date from the late 1980s, probably discarded from garden ponds and aquaria; for sale in garden centres as an oxygenating plant, and also introduced for water purification schemes. Many records are from the last 5 years (black dots at right).

Lough Corrib has become infested over the past 2 years, creating a major catastrophe for fisheries in the lake. Lagarosiphon in Rinneroon Bay, Lough Corrib - 2006 (above)

As with many other aquatic weeds, Lagarosiphon is effectively sterile, since only female plants are present, but grows at a phenomenal rate, and fragmentation due to boating activities, wildlife and wave action, leads to rapid dispersal.


This species is distinguished from the other invasive pondweeds Elodea and Egeria by the leaves being spirally arranged on the stems, and not whorled.
(Left to right: Elodea canadensis, Egeria densa, Lagarosiphon major)


Case Study on Lagarosiphon major in Lough Corrib. Joe Caffery, Central Fisheries Board.
In those areas where Lagarosiphon is well established in Lough Corrib, preliminary studies have revealed that it has a significant negative impact on indigenous macrophyte communities. It is anticipated that the impact on natural indigenous fish communities in the lake will also be significant ... Click here to download the case study and read more on the Lagarosiphon issue in Lough Corrib, County Galway.

Clayton J. & Franklyn G. (2005) Assessment of Lagarosiphon major control in Lake Wanaka, South Island, New Zealand. Comparison of two methods of control: suction dredging (which was successful with some colonies) and application of diquat herbicide (the results of which were variable, being successful in enclosed bays, but less successful elsewhere). Charophyte beds were not impacted by diquat, even when directly exposed within treatment areas.

Global Invasive Species Database

CAISIE - Control of Aquatic Invasive Species and Restoration of Natural Communities in Ireland is an EU Life+ and Department of the Environment and Local Government funded programme which will contribute to the understanding and control of aquatic invasive species in Ireland, in particular that of Lagarosiphon major in Lough Corrib. A team of three researchers will be based at the Central Fisheries stores near Moycullen until 2013. The Casie website details the full extent of the project

Joe Caffrey of the Central Fisheries Board has been conducting extensive work in Lough Corrib (right) on potential control methods.

see: Central Fisheries Board Stop the spread of Lagarosiphon major

If you notice Lagarosiphon in any previously undocumented site please notify the following:-
The Lagarosiphon Task Force
c/o Dr. Joe Caffrey
Senior Scientific Officer,
Central Fisheries Board


Kathleen H Bowmer, S.W.L. Jacobs, and G.R. Sainty (1995). Identification, Biology and Management of Elodea canadensis, Hydrocharitaceae. J. Aquat. Plant Manage. 33: 13-19.

Clayton J. & Franklyn G. (2005) Suction dredging to control curly water-thyme Lagarosiphon major, an invasive waterweed, in Lake Wanaka, South Island, New Zealand.

Clayton J. & Franklyn G. (2005) Herbicide treatment to control curly water-thyme Lagarosiphon major, an invasive waterweed, in Lake Wanaka, South Island, New Zealand.