New Zealand Pigmyweed - Invasive Species Information
Reproduction: Tiny fragments of the stem can regrow and multiply into a dense mat of vegetation.
Zealand Pigmyweed Flower
Originally found in Australia and New Zealand, it has been introduced around the world. New Zealand pygmyweed grows in ponds, lakes, reservoirs, canals and ditches as well as on damp mud on the margins of ponds and reservoirs. It tolerates a wide range of conditions, from basic to acidic and oligotrophic to eutrophic.
This perennial plant forms carpets with 100% cover, or semi-submerged in deeper water, or totally submerged with elongated stems. It does not die back in winter.
New Zealand pygmyweed is also known as Tillaea aquatica, Australian Swamp-stonecrop, and Briweg.
How To Identify New Zealand Pigmyweed?
Stem: Pink, rigid and round
Leaves: Narrow and pointed up to 2cm long and in opposite linear pairs. Leaf bases joined around the stem to form a collar. Leaves are fleshy when emergent and flatter when permanently submerged
Flower: Very small star-like, with 4 whitish petals. Blooms between June and September. flowers are often absent
New Zealand Pigmyweed - Crassula helmsii ID Guide
New Zealand Pigmyweed Leaves and Flowers
Why Is New Zealand Pigmyweed A Problem?
Forms thick dense mats which can float or be submerged. The thick mats cause shading of existing water plants and the depletion of oxygen in the water, which leads to a reduction of native ora and fauna.
Possible health hazard, as the thick mats can be mistaken for dry land.
The species can move onto a terrestrial habitat after it colonises an aquatic area. Can obstruct boats and reduce the opportunities where fishing can take place, which may impact upon local economies.
What Is New Zealand Pigmyweed - (Crassula helmsii)?
Habitat: Aquatic, Freshwater
Distribution in Ireland: localised distribution in the wild but with many occurrences in arti cial waterbodies
Status: Established
Family name: Crassulaceae
European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)
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There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...
Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.
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American Skunk-Cabbage - Lysichiton americanus
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Red Alga - Grateloupia doryphora
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Waterweeds - Elodea (all species)