Most flowers are made to be seen. This one barely clears the ground. In late summer, small cups of flowers push through the leaf litter of North Island forest, with no stem and no green leaves of their own. After dark, they give off a strong scent of ripe melon.
This is Dactylanthus taylorii, pua o te rēinga, the flower of the underworld. The name refers to its flowers emerging from below ground. It is New Zealand's only fully parasitic flowering plant, and one of its rarest. Over the last century its two biggest threats have been possums, and people with spades.
A plant without leaves
Dactylanthus has no green leaves and no roots of its own. It grows as a root-like stem attached to the root of a host tree, drawing water and nutrients through the connection. It can live on around 30 kinds of native hardwood, among them five-finger, kōhūhū and broadleaf. The flowers are the only part of the plant visible above the ground.
Plants are either male or female, and they flower from late summer into autumn. A single plant can send up as many as 60 flower heads in a season, each one sitting in the litter like a small dark cup. It was once found from Northland to the Wairarapa, and in Kahurangi in the north of the South Island. Today it grows mainly in the central North Island, inland from the East Cape and through the Central Plateau.
A bat that walks
The flowers are pollinated by pekapeka-tou-poto, the short-tailed bat. New Zealand's two native bat species are its only native land mammals, and the short-tailed bat does something unusual for a bat: it spends much of its time foraging on the forest floor, folding its wings and moving through the leaf litter on all fours.
At night, the bat is drawn to the flowers by their scent and nectar. The plant flowers in the leaf litter, and its pollinator searches the same layer of the forest. It is a close relationship, and one that only works if both species are still there to keep it going.
What possums do
Possums browse Dactylanthus flowers, and a flower that has been eaten cannot go on to produce seed. Rats and pigs also browse the flowers. The Department of Conservation identifies possum browsing, and the resulting loss of seed production, as the greatest long-term threat to the species.
The difference is visible when possums are kept out. In experiments where Dactylanthus plants were protected from browsing animals, the plants inside the exclusion plots produced many more flowers than those left exposed. At Pirongia, where Dactylanthus is one of the threatened species DOC is working to protect, possum monitoring after control recorded no catches across 240 traps in three nights, compared with a 5.4% trap rate the previous year.
The wood roses
Where Dactylanthus attaches to a host tree, the tree's root grows around the connection and forms a distinctive fluted shape. These are the "wood roses" that gave the plant another name, and for much of the twentieth century they became objects to collect and sell.
The trade was closely associated with the central North Island. Collecting was described by DOC as a hobby among foresters and their families working in native forests, and wood roses were sold through curio and craft shops as souvenirs. Museum collections contain specimens collected in the central North Island during the 1960s and 1970s, suggesting the practice was still well established then.
Preparing one meant digging up the Dactylanthus and its host root. The plant tissue was then removed, leaving the woody structure behind. One collector used wire baskets lowered into the geothermal pools at Wairakei to strip the tissue from the roots. The finished wood roses were mounted and varnished, and were sold as souvenirs through shops, including at international airports and the Chateau Tongariro.
The trade continued into the 1990s, with DOC records from the period documenting wood roses still being offered for sale, although collection was declining. Every wood rose on a mantelpiece is a plant that was dug up and killed, and the digging damaged the roots of its host tree as well. Collecting is now prohibited on land administered by the Department of Conservation, and the specimens that remain in museums and private collections are records of a plant that was once treated as a souvenir rather than a threatened species.
Protecting the flower of the underworld
Dactylanthus is classed as Threatened – Nationally Vulnerable, with likely only a few thousand plants remaining. Some of the protection methods are straightforward: wire cages can keep possums away from individual plants, while hand pollination can increase seed production. Possum control across the wider forest protects plants that have not yet been found or monitored.
The possum fur in our knitwear comes from that same possum control. Our conservation page explains how it works, How possums conquered New Zealand covers how possums got here, and Beyond the kiwi looks at four more species they threaten.
With thanks to Ngā Manu Images for the photographs in this post.
Common questions
What is pua o te rēinga?
Pua o te rēinga, Dactylanthus taylorii, is New Zealand's only fully parasitic flowering plant. It has no green leaves or roots of its own, and grows attached to the roots of a native host tree, drawing water and nutrients from it. Only its flowers appear above ground, pushing through the leaf litter in late summer and autumn with a scent of ripe melon after dark. The name means "the flower of the underworld".
Why is Dactylanthus threatened?
Dactylanthus is threatened mainly because possums eat its flowers, and a flower that has been eaten cannot set seed. The Department of Conservation identifies possum browsing as the greatest long-term threat to the species. Rats and pigs also browse the flowers, and for much of the twentieth century plants were dug up for the wood rose trade. It is classed as Threatened – Nationally Vulnerable, with likely only a few thousand plants left.
What pollinates Dactylanthus?
Dactylanthus is pollinated by pekapeka-tou-poto, the short-tailed bat, one of New Zealand's two native bat species. The bat forages on the forest floor, folding its wings and moving through the leaf litter on all fours, and is drawn to the flowers at night by their scent and nectar.
What is a wood rose?
A wood rose is the fluted woody shape a host tree's root forms where Dactylanthus attaches to it. Through the twentieth century, wood roses were dug up, stripped of plant tissue, varnished and sold as souvenirs. Each one meant a plant had been killed. Collecting is now prohibited on land administered by the Department of Conservation.
Where does Dactylanthus grow?
Dactylanthus grows mainly in the central North Island, inland from the East Cape and through the Central Plateau. It was once found from Northland to the Wairarapa, and in Kahurangi in the north of the South Island. It can live on around 30 kinds of native hardwood, including five-finger, kōhūhū and broadleaf.
How is Dactylanthus protected?
Dactylanthus is protected with wire cages that keep possums away from individual plants, hand pollination to increase seed, and possum control across the wider forest. In trials, plants shielded from browsing animals produced many more flowers than those left exposed. Forest-wide control also protects plants that haven't yet been found.
Sources
- Department of Conservation. "Dactylanthus." doc.govt.nz
- New Zealand Plant Conservation Network. "Dactylanthus taylorii." nzpcn.org.nz
- New Zealand Geographic. "Flower of Hades." nzgeo.com
- Department of Conservation. "Bats/pekapeka." doc.govt.nz
- Department of Conservation. "Monitoring reveals possum reduction at Pirongia." doc.govt.nz
- Department of Conservation. "Dactylanthus taylorii Recovery Plan 2004–2014." doc.govt.nz
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