Isolated kiwi tree is home to green moths, imprisoned seed ... and possums

It's not often you can photograph open flowers on a tree laden with fruit. A typical flowering season is a few months, followed a few more months for the fruits to plump and colour up.

This particular plant, the Pūriri from New Zealand, is  unusual among the 300 or so species of Vitex, and for that matter the flowering plant world, in producing flowers year-round. It is also one of the few species of Vitex outside the tropics and subtropics, and the only one found in New Zealand.

Vitex lucens, the Pūriri or Kauere, is from the north tip of New Zealand's North Island. There was an early report, from 1906, from Australia's Norfolk Island but that was from a planted specimen. My pictures are from one of two very old specimens in Melbourne Gardens (this one is in the New Zealand Collection beds, the other is near Guilfoyle's Volcano, at C Gate).

The first scientific collection of Pūriri was in 1769, by Joseph Banks and Daniel Solander, when they visited Tolaga Bay in New Zealand aboard the HM Bark Endeavour. Solander identified it as Ephielis pentaphylla (a genus in the soapberry family, Sapindaceae). This is one of the unprepossessing specimens from that first gathering, held now in the herbarium collection at The Museum of New Zealand Te Papa Tongarewa.

Vitex is in the mint family, Lamiaceae, and you see that family connection in the flowers (think Salvia or the Australian native Prostanthera). In New Zealand, these flowers are pollinated by birds from the Honey-eater family, These flowers can be white and green in nature, but ours are a rosy as the fruits, which is more typical. I'm sure the honey-eaters prefer pink and red.

The cherry red fruits are eaten (and seed presumably distributed) in New Zealand by a native rat, the Kiore. Here in Melbourne Gardens they seem to be nibbled by some rodent or marsupial (see reference to possum, later in post...).

We now have eight individuals of this species growing in Melbourne Gardens, but even when we had a single specimen the fruit produced viable seed. So this species can 'self fertilise'.

However from a flower with four ovaries, the mature fruit will typically contain only one or two fertile seeds and these apparently rarely germinate under a mature tree. Part of the problem seems to be the seeds inability to escape from their nutty chamber.

These three woody flasks were extracted from ripe fruit on the ground. They don't seem to have yet developed into the flanged and often hooked final form.

As Eric Godley reported in his 1971 paper on fertility of the Pūriri, there are four openings in the mature nut, with each opening 'guarded by an oval door'. For reasons unknown to Godley, that door quite often doesn't open so so even fertile seed will 'perish within the imprisoning endocarp [stony layer]"

With their 'deep green foliage and regal grey trunks, puriri are', as described by Astrid Dykgraaf in New Zealand Geographic, 'princes among Northland’s trees'. Northland being that part of New Zealand where the Pūriri grows. 

We also learn in this article about the many uses of the durable wood by early Europeans, and the employment of its leaves as medicine by the Māori. The Māori did use the wood, but only sparingly.

Many species other than us depend on this plant. When I was at Otari-Winton Bush in New Zealand last year, I was shown a live Pūriri Moth, a rather large and green moth. It's larvae live on and eat Pūriri, and a few other species, and they used to congregate in large masses, like the Bogong Moth in Australia. Apparently this is no longer the case.

Although the species as a whole is not under threat of extinction in New Zealand, there is unexplained dieback of  Pūriri, and possums are rather fond of it. This has led to some concern about its long-term survival in farmed river flats and nearby hills.

It's worth looking after the Pūriri and its habitat for all kinds of reasons, including the conservation of the Pūriri Moth. Otherwise the only green moths you'll see will have a pin through them, as with these two stored along with the Banks and Solander specimen in Te Papa Museum.

Note: The image of the herbarium specimen was downloaded from Te Papa Collections online, with the kind permission of Te Papa under a creative commons licence.