Alsophila milnei
Common names
Milne’s tree fern
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Ferns
Simplified description
Tree fern with brownish-stalked soft leaves to 4 m long inhabiting Raoul Island in the Kermadec Islands. Trunk to 8 m tall, skirted by remains of old fronds. Leaf stems covered in wavy hairs (lens needed). Sporangia arranged in small small deep cups underneath fronds.
Detailed description
Tree fern up to 10 m tall. Trunk scaly, bearing numerous stub like, projecting stipe remnants. Stipes stout, initially evenly yellow, maturing pale brown, rugose, basally covered with persistent scales (usually with sparse caducous scales running along sides of the upper stipe and rachis); scales dark brown lacking marginal spines. Fronds up to 4 × 2 m, bright yellow green to somewhat milky-green above, paler beneath, held horizontally, 3-pinnate, coriaceous; dead fronds long persistent, forming a dense skirt around trunk. Primary pinnae up to 450 mm long, undersides bearing fine curly hairs. Indusia covering mature sori, opening to form a deep, cupular structure with a smooth rim. (Description adapted from Brownsey & Smith-Dodsworth (2000)).
Similar taxa
On Raoul Island this species is sympatric with Alsophila kermadecensis from which it differs by its smaller stature ( up to 10 cf. 20 m in A. kermadecensis), scaly rather than scaly and hairy stipes, horizontal rather than arching fronds which are retained rather than dropping when dead to form a skirt and pinnae undersides which have fine curly scales rather than scales whose apices are terminated by single or stellate spines. Alsophila milnei is very similar to A. tricolor which is endemic to New Zealand proper. It is easily distinguished from that species by the pale brown rather than silver stipe and rachis, and pale green rather than silvery-white colour of the pinnae undersides. However, in Te Paki especially, some populations of A. tricolor lack this colouration, and appear to be very similar to A. milnei—these plants require further study.
Distribution
Endemic. Kermadec Islands, Raoul Island only
Habitat
Most commonly found in the lower altitude, drier forested parts of Raoul Island. However, occasional plants are found also in the wetter, higher elevation forest.
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Naturally Uncommon | Qualifiers: IE
Threats
No apparent threats. It is a narrow range endemic naturally confined to Raoul Island where it is abundant.
Detailed taxonomy
Family
Synonyms
Cyathea milnei Hook.f.;
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Propagation technique
Easily grown from spores. Initially plants are cold and drought sensitive. However once established this species is very fast growing. It prefers semi-shade in a warm, sheltered site. It should be planted in a free draining, moist soil. Once established it can tolerant drought but it should not be allowed to dry out for too long. Although more cold tolerant that Alsophila kermadecensis it is best grown in warmer climates.
Other information
Cultivation
Occasionally available from specialist native and general plant nurseries
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
CYAMIL
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Naturally Uncommon | Qualifiers: IE
2012 | At Risk – Naturally Uncommon | Qualifiers: IE, OL
2009 | At Risk – Naturally Uncommon | Qualifiers: IE
2004 | Range Restricted
Referencing and citations
References and further reading
Brownsey PJ, Smith-Dodsworth JC. 2000. New Zealand Ferns and Allied Plants. David Bateman, Auckland, NZ. 168 p.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange July 2009. Description adapted from Brownsey & Smith-Dodsworth (2000).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Alsophila milnei Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/alsophila-milnei/ (Date website was queried)