Graham Dyer reckons he has been the right person to grow the world’s only outdoor collection of kauri trees because he has “two problems” – once he gets hold of an idea he doesn’t let go, and he doesn’t take no for an answer.

The Omanawa kiwifruit orchardist has been collecting kauri (Agathis species) for 12 years after realising the only collection was grown indoors at Amsterdam University’s botanic gardens (Hortus Botanicus, website is in English).

“Tauranga is the southern boundary of where kauri grow naturally in New Zealand,” Graham says, “and Omanawa is pretty much the actual southern boundary. I don’t know whether other people think this makes Tauranga important, but I do.”

Mavis and Graham Dyer in their home kauri grove. Photo: Sandra Simpson

Graham has gifted a collection of kauri from around the Pacific to the in-development Sydenham Botanic Park in Tauranga.

Kauri grow happily as far south as Stewart Island, he says, but have been planted there and need nurturing in their early years to get them to maturity.

And while tree collecting may sound like a gentleman’s hobby, the reality is that it’s expensive, hard work and fraught with difficulty.

One kauri native to Vanuatu grows in such a remote location that some of the tribes in the area have never seen white people.

“Agathis macrophylla is found only in the mountains, and we’re talking serious mountains with high rainfall and cloud peaks. I’m too old to go in where there are no tracks and you only make 2km in a day.”

He and his wife Mavis have made Vanuatu their second home and have an adopted son, Malcolm, from the island of Espiritu Santo. Malcolm has gifted them customary land and Graham has planted kauri there, too.

“Fortunately, I understand how Second World people operate,” he says of his seed collecting. “You have to do everything on a person-to-person basis – letters aren’t replied to and phonecalls aren’t returned. You have to do it in person. If you’re standing looking at them, it will work.

“But it’s intimidating to be told the kauri seeds are ready – and they’re 60m up in the tree.”

Timing is everything. “The trees drop their seeds when it’s wet and every country has a different wet season – October in Malaysia, December in Papua New Guinea and March in New Zealand.”

The seed has a maximum viability of three weeks, “which is why rain is so important – the seeds germinate immediately and you can see them in four or five days”.

Graham was one of the original Tauranga Tree Society planters at McLaren Falls Park, responsible for sourcing exotic trees, including importing seed, so when he turned to Agathis he had a head start on knowing where to go to get seeds.

Araucaria hunsteinii is native to the mountains of Papua New Guinea and is a tree threatened by habitat loss. Photo: Sandra Simpson

Araucaria hunsteinii is native to the mountains of Papua New Guinea and is a tree threatened by habitat loss.

He’s also a keen collector of the Araucauria family, which includes Norfolk Island pine (Araucauria heterophylla) and monkey puzzle (Araucauria araucana), but discovered an oddity over the seed of the monkey puzzle tree native to the Andes.

“You can’t bring it in from Chile under Cites regulations [an international embargo on the trade of endangered animals and plants], but traditionally the seed has been used by the Indians as a food source and it turns out you can import it as a food.”

Graham has collected kauri from Malaysia, Indonesia, Australia (where the three varieties are native to Queensland and Agathis atropurpurea grows in a single, small area), New Caledonia and Vanuatu (which also shares a variety with Fiji). There are also kauri native to Papua New Guinea, the Solomon Islands and the Philippines.

Agathis corbassonii is native to New Caledonia. Photo: Sandra Simpson

Despite “an expert” warning Graham that tropical kauri wouldn’t grow here, he’s found they grow faster than they do in their home environments.

He also points out the trees are hardier than we might expect – Agathis robusta (Queensland kauri) seedlings planted in the 1940s in the Waipoua Forest (home to this country’s two largest native kauri, Tane Mahuta and Te Matua Ngahere) never grew because they were covered by undergrowth, particularly manuka.

Tane Mahuta towers over a visitor. Photo: Sandra Simpson

“They went into hibernation for 60 years,” Graham says, “and when that manuka went, away they went. It was like they had been planted yesterday. They will tolerate dark like no other plant because they’ve been through periods of total darkness and they have that genetic memory.

“They have survived long periods of climate change and adapted. Modern plants live by the seasons, while ancient kauri have adapted to the triggers of light and rain. They’re not interested in hot and cold.

“The species is 200 million years old, it’s been through all sorts of climate change – knowing what to do to survive is in their genetic memory.”

Agathis trees:

• Have been around since the Jurassic period
• Comprise 21 species; only Agathis australis is native to New Zealand but it is the largest Agathis
• Are found from Malaysia and the Philippines (north) to New Zealand (south, the only non-tropical site); in Melanesia but not Polynesia
• Grow from sea-level to 2500m elevation
• Are evergreen trees with very straight trunks, they lose their lower limbs as they grow (the juvenile stage can last 100 years)
• Are prized for their timber with many species are now endangered.

Less than 4 per cent of New Zealand’s kauri forest remains, thanks mostly to the logging activities of the 19th and early 20th century, with the trees now under threat from kauri dieback disease. Agathis is Greek for “ball of thread”, referring to the shape of the female cones.

This article was originally published in the Bay of Plenty Times and appears here with permission. It has been edited slightly.