New Zealand's underground parasite plant pollinated by bats

A parasitic plant that is pollinated by the short-tailed bat is now only found in a few spots across the North Island, but was once widespread across both islands

The dactylanthus is New Zealand's only indigenous, fully parasitic, flowering plant, and Department of Conservation Hauraki operations manager Avi Holzapfel works to protect them.

The Māori name for the plant is pua o te reinga - flower of the underworld - which relates to the way its flowers emerge from below ground.

Holzapfel told RNZ First Up it is also called waewae te atua, meaning the legs of the gods.

"It's a very unusual plant and most people wouldn't recognise it as a flowering plant," he said.

"It looks when you come across it like a warty bit of wood or like a root burr. But it's an underground plant that lives on the roots of host trees. It's a parasitic plant, which means that it's fully dependent on these trees for its survival, mainly completely underground.

"Only when it flowers, it comes above the forest floor."

The underworld plant can only be seen by those who are lucky enough to see it in flower, or if they can see an exposed part of the plant's body.

"When it flowers it has a very strong smell, a very sweet smell, a bit like ripe melon or over ripe fig."

When it is not flowering, humans cannot smell the plant - but pigs can.

It is a very unique type of parasitic plant that does not occur anywhere else in the world, Holzapfel said.

"It has no green leaves. It doesn't produce chlorophyll when it grows, it grows together with the host root. It doesn't harm the host. Doesn't harm the tree.

"And then when it flowers, it produces these enormous amounts of nectar at a time when hardly anything else flowers in autumn in New Zealand. And so lots of animals are using the nectar and feed on it.

"It's a little bit like a meeting point on the forest floor, like a pub."

There is another part of the pua o te reinga story that is unique, Holzapfel said. The plant is pollinated by the New Zealand short tailed bat.

"It's probably one of the only flowering plants that's pollinated by bat on the ground.

"Because bats normally fly around and pollinate things in flight, but in this case our bat is really well adapted to crawling on the forest floor.

"It sort of crawls on its elbows. It seeks out the dactylanthus and it feeds on the nectar, and while doing that it gets pollen on its face and flies to another plant and puts the pollen there.

"That's the one pollinator that we know of. I'm pretty sure there are other pollinators as well that we just haven't seen."

The flower of the underworld grows in the North Island only, in a few spots including the Central Plateau, East Cape and Little Barrier Island. But once upon a time it was widespread across both islands, Holzapfel said.

"It's not as common as it should be and it's not limited by habitat because the host trees that it grows on, they are everywhere. We don't have any shortage of whole trees.

"It's the lack of reproduction that makes it so endangered today, and that mainly comes from browsing by introduced puzzles, rats and mice."

Holzapfel said people can get involved in helping to bring the flower of the underworld to more areas of the country.

"We're trying to now increase the population - basically creating new plants, new populations, and you can do it by taking seed and sewing it into suitable places where there are host trees.

"The places where we've done it, quite a few of them have been successful. And the beauty is that those young populations there will be probably there for 30-40 years. So the plants are very long lived and that is a long time to again produce seeds and you basically take that seed and put it somewhere else.

"You can grow them exponentially once you've established them in a new place. So it's feasible. Otherwise the plants are just getting older, and the older they get, the fewer female flowers they get and the fewer chances they have to actually reproduce."