Lagarosiphon - Association pour la Sauvegarde du Léman

Census of Lagarosiphon major

Assessment of the presence of this aquatic invasive alien plant in the ports of Vaud and Valais on the Lake Geneva region.

listed ports

volunteers

half-days in the field

This participatory science project, commissioned by the Biodiversity and Landscape Division of the canton of Vaud and by the Forest, Nature and Landscape Service in the canton of Valais has given us a picture of the extent of the spread of Lagarosiphon major in the areas most conducive to its colonisation, thanks to the participation of 50 volunteers in the field.

The campaign ended in September 2024.

What is Lagarosiphon major?

Origin and description

Native to the African continent, the large lagarosiphon is a fast-growing submerged aquatic plant.
It settles in the sediment and develops long stems up to 5 m long.
The leaves are narrow lanceolate, even linear and finely toothed. They are arranged in a spiral on the stem, except towards the top. The top of the stem is very dense and almost resembles a feather duster.

Botanical information

Accidental introduction through cleaning and emptying of aquariums and garden ponds
Spread by water sports equipment to other bodies of water by pieces of plant left on water sports and leisure equipment (Leisure, diving, fishing).

The danger it represents

For biodiversity

Competitive: fast-growing, highly adaptable, no predators
High density: very dense, dominating the other species in the meadow
Blocking light: weakening native plants
Reduces water quality: decomposition of plants leading to a reduction in oxygen concentration

Economically

Slower flow : increase in silt deposition, which can have an impact on flood control
Interferes with navigation, locks and leisure activities: reduced tourist appeal due to unpleasant odours (decomposition)
Reduces the aesthetic value of banks, watercourses and ponds: uniform colonisation by the same species

Possible confusion

Lagarosiphon major can be confused with Canada elodea (elodea canadensis) and Nuttall's elodea (elodea nuttallii), which are also invasive.

The difference lies in the arrangement of the leaves: elodea leaves are at the same level (whorled) in groups of 3, while Lagarosiphon major leaves are arranged in a spiral along the stem.

Menu

Census of Lagarosiphon major

What is Lagarosiphon major?

Media gallery

Close

Menu

Census of Lagarosiphon major

What is Lagarosiphon major?

Media gallery

Subscribe to the ASL newsletter

Close

The association

Biodiversity

Actions

Raising awareness

Support us