Buccaneers of NZ flora

Clips of Dunedin's snow-covered hills and icy roads are a time-honoured winter tradition on New Zealand television - as are regular jibes from northerners about the city's "fresh'' weather.

To be fair, we do live in the coolest part of New Zealand. On a globe, the southern South Island looks a bit like a big toe dipping into the icy seas around Antarctica. With that in mind, would you believe that despite Dunedin's modest summer temperatures, its average midwinter temperatures are roughly the same as those of Madrid, Bordeaux, Florence, Istanbul and Aleppo? It's true.

That's why we can get away with growing so many sub-tropical - and even a few tropical - plants outside in sheltered places, even if their fruits seldom ripen. You can see fine local specimens of pohutukawa, kauri, puriri and taraire trees from the north of the North Island, too.

I even grew a little New Zealand mangrove seedling in a bowl of salty water by my desk for a few years. It wouldn't have survived outside in a southern winter, but almost all other New Zealand trees would - and actually do - so long as they are planted in the right place.

With its big, leathery, green paddles, puka or pukanui (Meryta sinclairii) looks like a castaway that was left behind by tropical seafarers a long time ago. Even more so when you find out that it originally grew only on the tiny Three Kings Islands/Manawatawhi just off the northern tip of the North Island.

Abel Tasman and his crew sighted those 13 little islands on January 6, 1643, the date of the Twelfth Night Feast of the Epiphany. In the Christian tradition, that date commemorated the visit by three wise men (or kings) to the infant Jesus, so Tasman called them the Three Kings Islands. They're about as far from Cape Reinga as Milton is from Dunedin.

Interestingly, Tasman and his crew also saw some Maori on the islands. Maori were no longer living there by the time the Treaty of Waitangi was signed in 1840, but it's thought that they brought pukanui seeds to the Hen and Chickens Islands near Whangarei and a couple of other places in the North Island some time before then. British settlers in Northland and Auckland soon took a shine to this flamboyant little native tree, and it has become a garden favourite wherever it can survive winter frosts.

We can just get away with growing pukanui in coastal Otago. It copes reasonably well with the average Dunedin winter, even though some of its leaves will die or turn brown from frost damage. It's the very severe air frosts that come along every 10 years or so that are the real problem. They can be killers for warm climate plants such as pukanui, as they were in 1996 and 2007. Are we overdue for another one, I wonder?

In the meantime, a trio of promising youngsters adorn the front garden of a house near the St Clair Esplanade, and there's one doing quite nicely beside a house near Cargill's Castle, but the biggest pukanui I've seen locally is in Waverley. You might not call it a tree yet, but it's well on its way.

Pukanui are in the same Araliaceae family as lancewood, five finger, Fatsia japonica and ivy. I think it's fair to say that none of those plants are grown for their tiny flowers or squishy dark berries, but they do all have leathery evergreen leaves with interesting shapes. The old, spreading pukanui trees dotted around Auckland exude a kind of languid, tropical vibe that's rare in New Zealand plants.

Taking a wee flight of fancy, I see pukanui as the buccaneers of the New Zealand flora, hiding on deserted islands in the warm seas of the north, unfurling their sails to catch the attention of any passing boats, and scattering their dark seeds like grapeshot as they conquer the mainland.

All health to them and their kin!