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Curly Waterweed - Invasive Species Information

High Risk

What Is Curly Waterweed - (Lagarosiphon major)?

Habitat: Aquatic, fresh water
Distribution in Ireland: Sparse distribution but locally abundant in some places

Status: Established
Family name: Hydrocharitaceae

Reproduction: All reproduction is by fragmentation or vegetative reproduction.  Detached stems, when they sink, root from the nodes and establish new populations

Curly Waterweed - (Lagarosiphon major)

Curly Waterweed

Originally from Southern Africa, where it is regarded as a nuisance weed. 

The plant can grow in water up to 6m deep. 

 

Curly waterweed is a perennial, submerged dioecious plant with branched stems and strongly recurved leaves alternate or spiralled or rarely in whorls up the stem, with two rows of fibre-like cells on the margins with > 50 teeth on each side.

 

It occurs in still or very slow-flowing water, principally in eutrophic, calcareous canals, ponds, lakes and gravel pits. 

How To Identify Curly Waterweed?

Leaves: Strongly recurved dark green leaves borne in a spiral arrangement, slight yellow tinge from the underside. 

Stem: The long stem is brittle and easily broken (aiding dispersal).

Size: Can grow in water up to 6 metres deep 

Curly Waterweed Leaf
Lough Corrib Ireland After Infestation
Lough Corrib Ireland Before Infestation
Curly Waterweed - Lagarosiphon major ID Guide

Curly Waterweed - Lagarosiphon major ID Guide

Lough Corrib Ireland Before Infestation

Lough Corrib Ireland After Infestation

Curly Waterweed Leaf

Waterweed Identification, Ireland

Why Is Curly Waterweed A Problem?

Plant stands produce dense canopy vegetation on the water surface and displaces native species. 

 

In high densities it blocks light from penetrating the water leading to a disturbance in the food web and a decrease in biodiversity.

 

It interferes with commercial navigation and water-based recreation. It has a negative impact on some native fish species. Native macroinvertebrate community structures are altered. 

National Biodiversity Data Centre Ireland - Recognised Invasive Plant Species.

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There are currently 35 invasive plant species identified as high risk on Ireland's biodiversity control list. Here's the A to Z of plant species included on the list (updated 2017)...

Click on a species from the following list to find out more

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  1. American Skunk-Cabbage - Lysichiton americanus

  2. Brazilian Giant-Rhubarb - Gunnera manicata

  3. Broad-Leaved Rush - Juncus planifolius

  4. Cape Pondweed - Aponogeton distachyos

  5. Cord-Grasses - Spartina (all species and hybrids)

  6. Curly Waterweed - Lagarosiphon major

  7. Dwarf Eel-Grass - Zostera japonica

  8. Fanwort - Cabomba caroliniana

  9. Floating Pennywort - Hydrocotyle ranunculoides

  10. Fringed Water-Lily - Nymphoides peltata

  11. Giant Hogweed - Heracleum mantegazzianum

  12. Giant Knotweed - Fallopia sachalinensis

  13. Giant-Rhubarb - Gunnera tinctoria

  14. Giant Salvinia - Salvinia molesta

  15. Himalayan Balsam - Impatiens glandulifera

  16. Himalayan Knotweed - Persicaria wallichii

  17. Hottentot-Fig - Carpobrotus edulis

  18. Japanese Knotweed - Fallopia japonica

  19. Large-Flowered Waterweed - Egeria densa

  20. Mile-a-Minute Weed - Persicaria perfoliata

  21. New Zealand Pigmyweed - Crassula helmsii

  22. Parrots Feather - Myriophyllum aquaticum

  23. Red Alga - Grateloupia doryphora

  24. Rhododendron - Rhododendron ponticum

  25. Salmonberry - Rubus spectabilis

  26. Sea-Buckthorn - Hippophae rhamnoides

  27. Spanish Bluebell - Hyacinthoides hispanica

  28. Three-Cornered Leek - Allium triquetrum

  29. Wakame - Undaria pinnatifida

  30. Water Chestnut - Trapa natans

  31. Water Fern - Azolla filiculoides

  32. Water Lettuce - Pistia stratiotes

  33. Water-Primrose - Ludwigia (all species)

  34. Waterweeds - Elodea (all species)

  35. Wireweed - Sargassum muticum

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