Norfolk Island ferns

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Norfolk Island ferns

Three Te Papa botanists recently visited Norfolk Island together with colleagues from the Royal Botanic Gardens Victoria. Their purpose was to collect ferns for research. Curator of Botany Leon Perrie introduces the significance of Norfolk Island’s ferns.

Our research programme investigating the relationships and naming of Aotearoa New Zealand’s ferns depends on also understanding the ferns of the surrounding landmasses. For example, more than half of New Zealand’s indigenous ferns are thought to also occur naturally elsewhere, especially south-eastern Australia and the Pacific Islands.

Two people walking through a forest. One has a hat on. They are looking at ferns.
Collecting Asplenium australasicum on Norfolk Island. Photo by Lara Shepherd. Te Papa

While we’ve been involved with many studies of Australian and Pacific Island ferns, samples from Norfolk Island have been mostly missing from our work – until now.

Norfolk Island

Norfolk Island is a small archipelago with a land area of about 35 km2 and a volcanic origin within the last few million years. It lies on the otherwise submerged Norfolk Island ridge between New Zealand and New Caledonia, and is an external territory of Australia.

Lara Shepherd has written about some of the interesting flowering plants found on Norfolk Island, along with the iconic Norfolk Island pine.

Despite its small area, about 45 species of ferns (and lycophytes) are native to Norfolk Island, compared with 204 for New Zealand.

Three people sitting outside on a patio going through bags of plant samples and pressing leaves in newspaper.
Processing a day’s collections, with fronds added to a herbarium press and subsamples dried in silica gel for later DNA analysis. Photo by Lara Shepherd. Te Papa

Fern names belonging to Norfolk Island

One of the reasons why the ferns of Norfolk Island are significant is that several scientific names of wide-ranging species ‘belong’ to Norfolk Island. That is, the type specimen(s) for the names were collected from Norfolk Island. It is as many as seven and reflects that European settlement of Norfolk Island was comparatively early for the region.

All photos are from Norfolk Island unless specified. The colloquial names are those from Norfolk Island.

A side-by-side comparison image of fronds from two ferns.
Trichomanes endlicherianum (left from Norfolk Island, right from New Zealand). The type specimen for the name is from Norfolk Island. We already knew from DNA analyses that plants called Trichomanes endlicherianum in New Zealand are actually a distinct species from those called the same name in Fiji and the Marquesas Islands. We’re looking forward to determining which is related to the Norfolk Island plants and therefore gets to keep the name. Photos by Leon Perrie. Te Papa

Flora of New Zealand page for Trichomanes endlicherianum.

A large green fern frond that has opened up.
King fern, Ptisana salicina. Another species whose scientific name is based on a type specimen from Norfolk Island. Norfolk Island and New Zealand plants, where it is also known as para, look very similar, but we recently separated plants from New Caledonia that had been attributed to Ptisana salicina as a separate species – Ptisana soluta. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Ptisana salicina.

Fern fronds and bush undergrowth as well as dead leaves.
Bats-wing fern, Histiopteris incisa. We contributed to a recent study that showed that Histiopteris incisa should be separated into two species. A name published in 1833 from Norfolk Island may be relevant for the second species depending on the relationships of the Norfolk Island plants, which have not been investigated until now. Known as mātātā in New Zealand. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Histiopteris incisa.

Ferns endemic to Norfolk Island

Also significant is that six fern species (and one subspecies) are endemic to Norfolk Island. Although found naturally only there, all have close relatives in Australia or New Zealand.

Two fern fronds next to each other. One is glossy and has bigger leaves and one is more closed up.
Two-frond fern, Asplenium dimorphum. The frond segments making spores are strikingly much narrower than those that are not. Photo by Leon Perrie. Te Papa

Asplenium dimorphum is one of the parents of the widely-cultivated false hen and chickens fern, Asplenium ×lucrosum. The other parent is Asplenium bulbiferum, the ‘true’ hen and chickens fern, which is endemic to New Zealand.

Te Papa blog post about the origins of Asplenium ×lucrosum.

After our role in elucidating the identity of Asplenium ×lucrosum, we were pleased to see Asplenium dimorphum in the wild for the first time. It’s a common species on Norfolk Island, and perhaps the most iconic of the ferns there.

A person is standing on a path surrounded by very tall tree ferns.
Norfolk Island tree fern, Cyathea brownii. New Caledonia, New Zealand, and Norfolk Island each claim one of their own tree ferns to be the world’s tallest. Cyathea brownii can certainly be tall – note the person on the path in this photo. But from what I’ve seen, and in lieu of verifiable measurements, I suspect the title belongs to New Caledonia’s curiously named Cyathea intermedia. Photo by Leon Perrie. Te Papa
A darker green fern frond in bush surroundings.
Shield fern, Parapolystichum calanthum. I’m probably one of the few people who could be excited about this species. However, it belongs to a group of closely related Australasian species that have perplexed me for over a decade. I’ve previously worked with only herbarium specimens of Parapolystichum calanthum. Seeing living plants for the first time helped me clarify the differences. Photo by Leon Perrie. Te Papa
A light green fern frond in bush surroundings.
King’s brake fern, Pteris kingiana. The fronds have fewer primary pinnae divided into tertiary segments compared to the similar Pteris tremula (see below). Pteris kingiana is named for Philip Gidley King, who was superintendent for the first European settlement on Norfolk Island – a penal colony to harvest the pines and flax. Photo by Leon Perrie. Te Papa
A split image of a fern frond and then a close-up of the veins on the leaves.
Netted brake fern, Pteris zahlbruckneriana. The netted veins distinguish this from the other Pteris species on Norfolk Island. It is part of the Pteris comans group, in which we have recently segregated the Australian and New Zealand members as separate species. Photo by Leon Perrie. Te Papa
Long, skinny fern fronds growing off a tree trunk.
Hanging fork fern, Tmesipteris norfolkiensis. We were pleased to find this in some abundance, epiphytic on the trunks of tree ferns. It was the final Tmesipteris species to sample for a DNA sequencing project by a wider collaboration. It may also resolve the identify of some mystery plants in Northland. Photo by Leon Perrie. Te Papa

Ferns shared by Norfolk Island and New Zealand

The following are some of the fern species indigenous to both Norfolk Island and New Zealand.

A horizontal-split image of a close up of leaves coming off a fern frond. The second image is an even closer look at the leaf pattern.
Sickle fern, Asplenium polyodon (Norfolk Island at top, New Zealand at bottom). Our earlier DNA sequencing work showed that Australian and New Caledonian plants are distinct from those in New Zealand. Our Australian colleagues were adamant during our visit that Norfolk Island plants looked different from those in Australia. But there looks to be differences with New Zealand plants too. A complication is that it is unclear where the type specimen originated and therefore to which landmass the name ‘belongs’. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Asplenium polyodon.

A fern frond lying close to the ground which is mainly earth and dead wood.
Tender brake fern, Pteris tremula. Fairly uncommon on Norfolk Island, but in New Zealand, where it is also known as turawera and shaking brake, this species has weedy tendencies and readily makes itself at home in and around gardens. Also indigenous to mainland Australia, Lord Howe Island, Vanuatu, and Fiji. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Pteris tremula.

Fern fronds growing around a tree trunk.
Climbing fern, Arthropteris tenella. Common in the remnant forest on Norfolk Island, scrambling over rocks and climbing tree trunks, but we curiously saw very few plants producing spores. Besides New Zealand, also indigenous to mainland Australia and Lord Howe Island. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Arthropteris tenella.

Ferns not shared with New Zealand

Norfolk Island also shares several ferns with other places that are not in New Zealand, such as the following. New Zealand is probably too cold.

Large dock leaves sprouting near the roots of a tree.
Dock, Asplenium australasicum. Although common in cultivation, we did not encounter wild plants of this bird’s nest fern until our fourth day. While not widespread, it can be locally abundant, spectacularly adorning rocky bluffs. Also indigenous to Australia and New Caledonia, and maybe further afield. Photo by Leon Perrie. Te Papa
Wide fan-like fern fronds with small trumpet-like spore protectors that present a bit like flowers.
Small filmy fern, Trichomanes saxifragoides. Apparently not recorded recently on Norfolk Island, we found it at several sites, usually on rocks near ridges. The fingernail-sized fronds are an unusual shape for a fern, but the spores are produced within a protective tube that characterises the genus Trichomanes. Also indigenous to warmer areas of Africa, Asia, New Guinea, Australia, and into the Pacific Islands. Photo by Leon Perrie. Te Papa
A split image of grassy fern leaves growing off the side of a tree. The second image is a close-up of the frond leaves.
Tape fern, Haplopteris elongata. Quite unlike anything found in New Zealand, with the spores produced along the margins of the narrow, undivided fronds. This group of ferns is related to the Adiantum maidenhairs! Also indigenous to warmer areas of Africa, Asia, New Guinea, Australia, and into the Pacific Islands. Photo by Leon Perrie. Te Papa

Weedy ferns

Unfortunately, about 10 species of exotic ferns have established on Norfolk Island. Those that are actively spreading have the potential to displace native species. The following three examples are also weedy in New Zealand.

A fern growing beside a large rock. The fronds have green and red leaves near the tips.
Holly fern, Cyrtomium falcatum. Well-established in a limited area at Ball Bay, and also colonising some of the rock walls in Kingston. Indigenous to parts of Asia. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Cyrtomium falcatum.

A split image with the right image showing long, thin fronds growing up from the ground. The second image shows round tubers and the root system after being plucked from the ground.
Fishbone fern, Nephrolepis cordifolia. Indigenous to many tropical regions. Widely cultivated on Norfolk Island, this species is also invading indigenous forest where is can be easily confused with the very similar-looking Nephrolepis flexuosa that is indigenous and rare. Nephrolepis cordifolia is a difficult weed to control because it forms tubers on its runners. Tubers left in the soil can resprout. The best way to distinguish the native Nephrolepis flexuosa is that it has no tubers. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Nephrolepis cordifolia.

The entire image is taken up with small rounded leaves with some of them rotting.
Salvinia ×molesta. We saw this floating fern clogging some of the waterways in the heritage area around Kingston. In New Zealand, it is illegal to sell, propagate, or spread this plant, and any sightings should be reported to Biosecurity New Zealand. They will coordinate its eradication. Photo by Leon Perrie. Te Papa

Flora of New Zealand page for Salvinia ×molesta.

Acknowledgements

Thanks to: our colleagues Daniel Ohlsen and Misha Chute from Royal Botanic Gardens Victoria; Kevin Mills for sharing information about Norfolk Island’s ferns before our trip; and to the local rangers for their support.

Three people are crouching around a mossy rock looking at a fern. One of them is taking a close-up photo with her phone.
Examining the easily overlooked Trichomanes saxifragoides. Photo by Lara Shepherd. Te Papa

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