These may be the first records of Pteris umbrosa R.Br. naturalised in New Zealand.
The plant of the two top images is the child of one I grew from a prothallus I discovered in the pot of a small Australian cycad I bought at a local big-box store. I suspect the cycad had been imported by a firm in New Plymouth.
This original plant I had growing in full sun behind a window and it grew profusely. It was hugely fertile and there was a mass of spores beneath it; and they found their way into other pots. Just as well, as the original plant used water at such a high rate that a little neglect on my part lead to its death from drought.
The other plant, (lower two photos) is in a much shadier spot and has not produced spores yet. In my opinion, it resembles the images of ferns to be found on the internet under this name. These all seem to be growing in shady forest sites.
I suspect that it is also a species of warm swamp margins and is capable of extremely rapid growth and high spore production; all good survival strategies where swamps may be ephemeral.
From my experience, the spores can lie happily dormant for at least 6 years, in neglected plant pots.
The bottom image is of a plant I found growing in the wild in Christchurch about two weeks ago (26 January 2010, about). For this very robust plant to be growing so well where I found it implies that there may be many more now in this city.
Let your mouse pointer rest on the link for a moment, then click on the link.
Use your browser back button to return. I have re-done the top two photos.