Macrolearia semidentata
Common name
Hangatere, Chatham Island aster, swamp aster
Synonyms
Olearia semidentata Decne., Olearia semidentata Decne. var. semidentata, Olearia semidentata var. albiflora Dorrien-Smith, nomen nudum, Eurybia semidentata (Decne.) F.Muell
Family
Asteraceae
Flora category
Vascular – Native
Endemic taxon
Yes
Endemic genus
Yes
Structural class
Trees & Shrubs - Dicotyledons
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.
OLESEM
Chromosome number
2n = 108
Current conservation status
The conservation 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.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – an interim threat classification status has not been assessed by the NZTCS panel.
- Conservation status of New Zealand indigenous vascular plants, 2017 . 2018. 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. 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, RR
Previous conservation statuses
2012 | At Risk – Naturally Uncommon | Qualifiers: IE, RR
2009 | At Risk – Naturally Uncommon | Qualifiers: IE
2004 | Range Restricted
Brief description
Small tree with narrow leathery saw-edged dark green leaves that are white underneath and large pinkish-purple daisy-like heads inhabiting swamps on the Chatham Islands. Leaves 3.5-7cm long by 0.5-1cm wide, widest at middle, with large thick teeth spaced along edge. Flowers 2.5-3.5cm wide.
Distribution
Endemic. Chatham Islands only
Habitat
More or less confined to restiad bog where it is one of three woody shrubs capable of growing amongst Sporadanthus traversii (the others are mataira karupuru (Myrsine coxii) and Dracophyllum scoparium). It is a rapid coloniser of burnt peat bog.
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]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Detailed description
Spindly, erect, sparingly branched shrub up to 2 m tall, trunk erect, slender and brittle; bark grey, grey-brown, chartaceous, flaking readily. Branches erect to suberect, (2–)4(–6) mm diameter, quadrangular, brittle, young branches densely invested in white floccose tomentum; tomentum discolouring and shedding in irregular patches as branch matures. Leaves alternate, subsessile, coriaceous; petiole if present, 1.5-2.6 mm long, plano-convex, densely covered in white, appressed to floccose hairs; lamina 30-74(-80) × 6-9(-12) mm, narrow-lanceolate, lanceolate to oblong-lanceolate, adaxially dark green, glossy, initially moderately densely to sparsely covered in white appressed floccose / lanate hairs, glabrescent abaxially, thickly covered in white, appressed hairs, margins weakly, rarely prominently, serrate in distal half to one third, teeth when present in (6–)8–10 pairs, sometimes entire; apex acute, subacute; base shortly attenuate. Inflorescences numerous at apex of branches, terminal, subterminal, axillary. Peduncules 50-80(-100) mm long, initially erect or curved, then spreading, slender (3–6 mm diameter), terete, white tomentose, bracteate, bracts 1-3-many, lanceolate, entire or toothed (2-3)4×, surfaces copiously white, tomentose. Capitula (30–)40 mm diameter. Involucrellum narrowly urceolate to obconic, involucral bracts imbricate, numerous, up to 10 mm long, narrowly lanceolate, deltoid, acute, abaxially maroon-black, covered in pilose / cob-webbed hairs, hairs especially prominent on margins; ray-florets (24-)26-30, 10-12 × 4-5(-6) mm, glabrous, linear-oblong, oblanceolate, apices obtuse, subacute or acute, usually minutely retuse, mucronate, mucro minute; surfaces initially purple, maturing lilac often fading to white tinged lilac; disc-florets(20-)22-26, corolla, magenta to violet-purple, anthers orange yellow, stigma dark magenta. Cypsela 2.5–4.2 mm long, narrowly oblong, narrowly obtriangular, obovate-triangular, compressed, often biconvex, base cuneate, ribbed 8–11, otherwise smooth, almost glabrous, sparsely furnished with short, white antrorse hairs, sparsely glandular, surface brown to grey-brown. Pappus 4.5–6.2 mm long, buff, pale orange-yellow.
Similar taxa
Easily distinguished from the other Macrolearia species by the spindly, sparingly branched shrub growth habit (specimens up to 2 m tall), short and dark mauve (rarely pink) ray florets. The leaves are also diagnostic in that they are oblanceolate with teeth present in the upper third of the lamina, while the teeth are not calloused and are distant from each other (see Saldivia et al. 2022). On the Chatham Islands hangatere (M. semidentata) could only be confused with keketerehe (M. chathamica). However, keketerehe is a much larger more heavily branched small tree (6–8 m tall) that usually forms a broadly domed canopy. The leaves of keketerehe are much longer, and more finely denticulate than those of hangatere which are shorter sparingly, or coarsely toothed in the upper half to third, while the capitula of keketerehe have dark aubergine coloured disc florets, and longer, narrower, white, white tinged pinkish (very rarely pale mauve) ray florets. Occasional hybrids between hangatere and keketerehe have been collected, notably from Rangaika where the ranges of both species overlap due to past land disturbance along the fringes of a restiad bog.
Flowering
November - March
Flower colours
Violet/Purple, White
Fruiting
January - June
Threats
Threatened by loss of habitat through peat bog drainage, over burning of restiad bog, accompanied by drying out of the peat soils, and also by browsing pressure from cattle.
Etymology
semidentata: Partially toothed
Where To Buy
Not commercially available.
Attribution
Fact Sheet prepared for NZPCN by P.J. de Lange 28 April 2022. Description by P.J. de lange (27 April 2022).
References and further reading
Saldivia, P.; Wagstaff, S.J.; Breitwieser, I.; Orlovich, D.A.; Lord, J.M. 2022: A Generic Taxonomic Synopsis of the Pleurophyllum Clade (Asteraceae: Astereae: Celmisiinae) with the Recognition of the New Zealand Endemic New Genus Macrolearia. Systematic Botany 47: 607–634
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Macrolearia semidentata Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/macrolearia-semidentata/ (Date website was queried)