Help with floating fern

I’ve recently learnt that the introduced Azolla pinnata (ferny azolla) has been found in the Wellington region. I’m interested in its distribution and would be grateful for help in looking for more. Azolla plants are fairly easy to spot: look for a red plant covering still bodies of water.

Azolla plants often become red in full sunlight, and they can become so abundant that they carpet ponds, drains, and other still bodies of water. This is Azolla rubra in a pond on Mana Island, Wellington. Photo Leon Perrie. © Te Papa.

Azolla are ferns, believe it or not! They are free floating, and while individual plants are only a few centimetres across, they can proliferate in good conditions to ‘carpet’ large areas of water surfaces.

There are two species in New Zealand: the native Azolla rubra (Pacific azolla, previously known as Azolla filiculoides); and the exotic Azolla pinnata, which is an introduction from the tropics.

Azolla pinnata has largely replaced the native Azolla rubra in the northern North Island. It is therefore a concern that A. pinnata was found near Waikanae in recent weeks, after being found near Whanganui a few years ago. It seems it is continuing to spread south.

The introduced Azolla pinnata has very regular branching. Plants can be red or green depending on whether they are in the open or shade, respectively. The green ovals are Lemna duckweed (a flowering plant). Photo Leon Perrie. © Leon Perrie.

The branching of the native Azolla rubra is irregular. Photo Leon Perrie. © Te Papa.

Can you help please?

I would like to better document the distribution of the two Azolla species in New Zealand, and particularly the spread of the introduced A. pinnata. The southern North Island is the primary interest, but anything that adds to what we already know would be useful (see the link to the map below).

Map of Te Papa’s collections of Azolla.

If you see Azolla (either species), you could post a comment or send me an email. If you have landowner permission, you could make a collection for possible addition to Te Papa’s specimens: post me 20-30 plants enclosed within a watertight plastic bag, with locality details, and your contact details. My address is: Leon Perrie, Te Papa, PO Box 467, Wellington 6011.

Thanks very much.

7 Responses

  1. Juliet K

    We have Azolla in Travis Wetland Reserve in Christchurch. Im almost definitely sure that they’re Azolla rubra as my park ranger project manager who works there said that they are the native Azolla. They’re quite abundant around the boardwalk areas that are boggy and swampy. I don’t think Ive seen any Azolla pinnata but I’ll have a closer look tomorrow

    Reply
    • Leon Perrie

      Hi Juliet,
      Thanks for that observation. Feel free to send me pictures for confirmation and/or post them to NatureWatch (http://naturewatch.org.nz/) for ‘crowd-sourced’ identification.
      Kind regards, Leon

  2. Elizabeth Beatson

    I have just cleaned out masses of oxygen weed from my garden pond and with it the covering of azolla. I am pretty sure it is rubra. With the oxygen weed gone the pump is working more efficiently and the azolla is somewhat more inhibited. I am just off SH1 on the north eastern side of Otaki.

    Reply
    • Leon Perrie

      Hi Elizabeth,
      Thanks for the report. Good to know the native species is still around.
      Leon

  3. adrienne dale

    HI leon

    There is heaps of A. pinnata in our ponds in Te Hapua Rd, Te Horo. I have been searching for A. filliculoides but can’t seem to find any. You are welcome to visit. See our website http://www.pateke-lagoons.co.nz

    Kind regards, Adrienne

    Reply
    • Leon Perrie

      Thanks Adrienne. We’ve had sightings from near there. Next time I head north, I might take you up on the offer to visit, as I would be interested to see how established the A. pinnata is. I would be interested to know if you do find A. rubra/filiculoides at your place, or if you see A. pinnata elsewhere.
      Kind regards, Leon

  4. Leon Perrie

    Note: the scientific name of the native species updated in this post to Azolla rubra from A. filiculoides, 2 April 2013.

    Reply

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