Metrosideros robusta
Past favourite plant finalist
Common names
northern rātā
Biostatus
Native
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified description
Tall forest tree that sends roots down a host tree which is eventually strangled bearing pairs of oval leaves with a small dent at the tip and masses of red bristly flowers in summer. Twigs square in cross section and fuzzy when young. Leaves 2.5–5 cm long by 1.5–2 cm wide.
Flower colours
Orange, Red/Pink
Detailed description
Stout tree 25–40 m tall, often starting life as epiphyte, so basal trunk is hollow, and composed of interlocking roots. Trunk 2–3–(4) m diameter. Bark firm, persistent, grey-brown, brown or rarely pale yellow, tessellated, shallowly furrowed, somewhat corky. Branchlets numerous, very twiggy (broom-like), puberulent with rust-brown hairs when young. Leaves (excluding water shoots) 25–50–(65) × (10)–15–25–(30) mm, leathery, dark-green, elliptic, ovate-oblong, to rhomboidal, apex obtuse, distinctly notched. Young growth pink, finely covered in rust-brown hairs, becoming glabrescent with age (hairs long persistent on midrib and leaf base). Water shoots: variable shape and size, glabrescent, pale green or yellow-green, delicate and wilting if detached from tree. Inflorescence a broad, terminal corymbiform, cymose, cluster of numerous flowers apically dominated by a temporarily dormant vegetative bud, which recommences growth following flowering. Pedicels 5–8 mm long. Hypanthia obconic, 9 mm long, sepals broad-triangular, petals shedding early, 2 × 3 mm, oblong, dark red, pink, orange or yellow, stamens numerous (25)–30–40 mm long, anthers versatile, pollen dark yellow to orange. Pistil similar length, stigma capitate. Ovary fused to hypanthium, ovules numerous. Capsules oblong 6–9 mm, distinctly raised above sepals and hypanthial rim. Seeds 2.5–5.5 mm, narrowly elliptic to linear, often twisted with apices usually curved or hooked.
Similar taxa
A distinctive species easily recognised by the small elliptic, ovate-oblong to rhomboidal dark green leaves, which possess a prominent apical notch. The young growth is often pink and is always finely covered in rust-coloured hairs. The hairs are slowly shed as the foliage matures but usually persists along the midrib and near the leaf base.
Distribution
Endemic. New Zealand: Manawatāwhi / Three Kings Islands, North Island (formerly widespread from Te Paki south to Wellington, now scarce over large parts of this range, and apparently absent from the Hawkeʻs Bay), South Island (abundant from Nelson west and south to Greymouth, from there locally common to about Hokitika, reaching a southern limit just south of Lake Mahinapua. In the east recently recorded from one site near Okiwi Bay, western Marlborough Sounds—though this site is unusual and may not be natural).
Habitat
Coastal and lowland forest occasionally extending to montane forest in some parts of the country. Once the co-dominant emergent tree of a distinctive vegetation type called rimu (Dacrydium cupressinum)/rātā 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.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – these interim threat classification statuses has not been assessed by the NZTCS panel.
- 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 – Declining | Qualifiers: CD, DPT
Threats
Northern rātā is most at risk from possum (Trichosurus vulpecula) browse. Possums can seriously damage and kill trees, and have, in some situations been directly responsible for the regional loss of northern rata. The species remains common over large parts of range, a situation being improved by the efforts of people encouraged by the national coordination of Project Crimson. Another threat to northern rata comes from hybridisation with pohutukawa (Metrosideros excelsa) which has now become established well south of its presumed natural southern limits. Ideally people should be discouraged from planting pohutukawa in places it is not natural to, especially when this borders habitats containing northern or southern rata (Metrosideros umbellata).
When myrtle rust (Austropuccinia psidii) was detected in New Zealand (May 2017) the conservation status was upgraded as a precautionary measure to ‘Threatened – Nationally Vulnerable’ because, on best advice, it was believed that no indigenous Myrtaceae had resistance to the myrtle rust disease (de Lange et al. 2018).
Myrtle rust (Austropuccinia psidii) is an invasive fungus that threatens native myrtle species. Learn more myrtlerust.org.nz.
Detailed taxonomy
Family
Myrtaceae
Synonyms
Metrosideros florida Hook.f.
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
(October)–November–January–(February)
Fruiting
(December)–January–(March)
Propagation technique
Very easy from fresh seed. Seed must be sown fresh, even if left for a few weeks before sowing viability can drop, especially if seed is allowed to dry out. Very difficult from cuttings, though soft wood water shoots give the best results. Can be grafted onto seedlings.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACU: Facultative Upland
Occasionally is a hydrophyte but usually occurs in uplands (non-wetlands).
Other information
Cultivation
Sold by a number of mainline and specialist native plant nurseries. However, many plants sold as northern rata are hybrids between it and pohutukawa.
Plant of the Month
This plant has been featured as a Plant of the Month – see Trilepidea: NZPCN newsletter for December 2012 for the full story.
Etymology
metrosideros: Iron heart
robusta: Sturdy
Manaaki Whenua Online Interactive Key
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.
METROB
Chromosome number
2n = 22
Previous conservation statuses
2017 | Threatened – Nationally Vulnerable | Qualifiers: DP, De
2012 | Not Threatened
2009 | Not Threatened
2004 | Not Threatened
Referencing and citations
References and further reading
Allan HH. 1961. Flora of New Zealand, Volume I. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. Government Printer, Wellington, NZ. 1085 p.
Beddie AD. 1953. Root behaviour in Metrosideros. Wellington Botanical Society Bulletin 26: 2–6.
Hosking G. 1994: Report on Northern rata dieback - Minginui faces. Department of Conservation Advisory Science Notes 66. 12 p. Available online in to parts: https://www.doc.govt.nz/globalassets/documents/science-and-technical/casn66.pdf, https://www.doc.govt.nz/globalassets/documents/science-and-technical/casn66a.pdf.
Sawyer JWD, Mckessar K. 2007. Northern rata (Metrosideros robusta): a species in decline? Wellington Botanical Society Bulletin 50: 48–55.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange (4 January 2004). Description adapted from Allan (1961).
Some of this factsheet information is derived from Flora of New Zealand Online and is used under a Creative Commons Attribution 3.0 New Zealand licence.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Metrosideros robusta Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/metrosideros-robusta/ (Date website was queried)