Plagianthus regius subsp. chathamicus
Chatham Island ribbonwood
Plagianthus chathamicus Cockayne; Plagianthus betulinus var. chathamicus (Cockayne) Cockayne
Vascular – Native
Trees & Shrubs - Dicotyledons
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.
2n = 42
Current conservation status
The threat classification status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley. Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – a suggested threat classification status has not been assessed by the NZTCS panel.
2017 | At Risk – Recovering | Qualifiers: CD, IE
Previous conservation statuses
2012 | At Risk – Recovering | Qualifiers: CD, IE
2009 | At Risk – Recovering | Qualifiers: CD, IE
2004 | Serious Decline
Tall tree with soft jagged pointed leaves and long sprays of tiny yellowish flowers and small green fruit that fall as a unit inhabiting the Chatham Islands. Wood soft. No marked juvenile growth form. Leaves 3-7.5cm long, much wider at base.
Endemic. Rekohu (Chatham), Rangihaute (Pitt), Maung’re, Tapuaenuku, and Hokorereoro (South-east) Islands.
Found on free draining, fertile soils throughout the main islands. Often an important species on soils derived from limestone, and basalt. This tree avoids poorly drained soils and peat.
Deciduous, dioecious, rounded or flat-topped trees 10−16(−18) m tall. Trunk up to 1 m d.bh., bark smooth, if torn peeling in long fibrous strips; surface brown-grey to grey, colour usually obscured by dense lichen growth (Amandinea, Bacidia, Lecanora, Pyrenula, Ramalina and Xanthoria species especially). Branches divergent to upright, often densely branched; branchlets, terete, pliant when young, brittle with age, if broken, leaving long tears of bark beyond damage point; initially finely pubescent, pubescent-villous, hairs grey-white, ± patent, hairs shedding with age. Buds, solitary, acute, densely covered in pubescent-villous, grey-white hairs; bud scales valvate (3−)4−5, (0.4−)0.6−0.8 mm long, deltoid, ± subulate, abaxially pubescent-villous, caducous. Leaves exstipulate, alternate distichous, ± closely spaced toward branchlet apices, soft and pliant, somewhat chartaceous with pinnate venation, surfaces finely pubescent when young, hairs shedding with age, ± glabrescent, adaxially light lime green to green, abaxially paler; midrib concolorous with lamina adaxially, paler beneath, not or scarcely raised above, distinctly so abaxially, finely pubescent, indumentum shedding in irregular patches with age; petioles, 15−20(−25) mm long, terete, finely pubescent, glabrescent. Lamina of juvenile 40−70(−80) × 26−34(−40) mm, of adult 70−90(−100) × 40−60(−65) mm; ovate, ovate-deltoid, apices acute to acuminate, base obtuse to subcordate, biserrate. Inflorescences axillary or terminal, borne in much-branched, suberect or pendent, compound, cymose panicles (65−)100(−140) × 80−100(−160) mm long, green to yellow green. Inflorescences axis terete, initially pubescent, indumentum shedding with maturity, leaving sparse to dense patches of patent hairs; branch axis, bracteate, bracts 3−5 × 3−6 mm, caducous, ovate-deltoid, deltoid, acute, surfaces finely pubescent. Flowers 5−6 mm diameter: ♂ yellow-green or greenish-white, sweetly scented; ♀ light green, without scent. Calyx campanulate to funneliform, 1.8−2.0 mm long, pale green or yellow-green, with 5 deltoid or oblong, acute or mucronate teeth. Petals 2.4−2.8 mm long (♂), 2.0−2.4 mm long (♀), spathulate-oblong, oblong, clawed, yellow-green, greenish-white or green, shedding after anthesis. ♂ with exserted staminal column, anthers 10−12, 0.3−0.5 mm long, sessile, pale yellow or yellow-orange, gynoecium vestigial, surmounting column. ♀ with androecium vestigial, forming a ring below stigma; stigma (3−5)−6, spreading, greenish. Fruits usually exserted from persistent calyx, 3−5 mm long, ovoid, apex acute.
Plagianthus regius subsp. chathamicus is one of the tallest trees on the Chatham Islands, and it is also the only deciduous one. The stout greyish trunk, broad canopy, lime green soft leaves with doubly serrated margins, and pendent greenish-yellow inflorescences and flowers readily identify it. In autumn the foliage turns yellow-green or yellow before falling. Plagianthus regius subsp. chathamicus is closely related to the Aotearoa / New Zealand subsp. regius, from which it differs by the lack of the filiramulate, divaricating juvenile growth habit (Cockayne 1912; de Lange 2008). Though the foliage of subsp. chathamicus is smaller than the adult, the branchlets are not interlaced; rather they tend to be erect and/or spreading. The juvenile state of subsp. chathamicus is usually very short-lived and is sometimes absent.
October - February
December - June
Easily grown from fresh seed. A very fast growing tree ideal for providing quick cover. Does best on free draining, but moist and fertile soils in full sun but can tolerate some shade.
Threatened from browsing by sheep, cattle and horses which browse foliage, ring bark or strip the bark off adult trees and kill seedlings. Pigs root up seedlings and saplings and may browse them as well. Possums browse foliage, flowers and seedlings. Land clearance for farming and fires are additional threats. Very few populations of manatu are secure from these threats on the islands.
plagianthus: Oblique or lop-sided flower (petals uneven at the base)
chathamicus: From the Chathams
Fact Sheet prepared for NZPCN by P.J. de Lange 12 May 2022. Description by P.J. de Lange.
References and further reading
Cockayne, L. 1912: Observations concerning evolution, derived from ecological studies in New Zealand. Transactions and Proceedings of the New Zealand Institute 44: 1–50.
de Lange, P.J. 2008: Plagianthus regius subsp. chathamicus (Malvaceae) - a new combination for the Chatham Islands endemic tree. New Zealand Journal of Botany 46: 381-386.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Plagianthus regius subsp. chathamicus Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/plagianthus-regius-subsp-chathamicus/ (Date website was queried)