Te Papa's Blog

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.