The dense covering of Azolla rubra water fern (and a little duckweed in the gaps) across the surface of the Heathcote River.
So much, you can't see the water.
M. Evangelista e D. Seglie
Accidental 'by catch' in sample of Lemna aff. disperma I have been cultivating since 15 November 2015 for suitable material for DNA sequencing
Fronds deltoid. Roots pinnate.
Azolla pinnata is generally regarded as an 'introduced' naturalized species to New Zealand - but I believe its more likely it self-introduced from Australia via the movements of trans-Tasman wetland birds such as grey teal (Anas gracilis). For me it is hard to understand how it was deliberately naturalized by people when it first appeared in New Zealand in the far north of the North Island (where many other accepted indigenous taxa shared with Australian first appeared (many of them aquatic) growing in places where trans-Tasman wetland birds are known to make landfall) and from where it has been spreading south ever since. This pattern is typical of a range of other wetland plants (e.g., Alternanthera denticulata, Juncus polyanthemus, Gratiola pedunculata; ferns (Blechnum neohollandicum, Christella dentata) and orchids (Cryptostylis subulata, Chilogottis formicifera, Pterostylis nutans, Thelymitra matthewsii and T. malvina, to name but a few) which are shared with Australia and which we accept as indigenous without question.
Whatever its biostatus - it cannot be denied that it is a very weedy and aggressive species in small ponds, lakes and slow moving water bodies.
Azolla (mosquito fern, duckweed fern, fairy moss, water fern) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like conventional ferns but more resembling duckweed or some mosses.