Macrolearia semidentata
Common names
Hangatere, Chatham Island aster, swamp aster
Biostatus
Native – Endemic taxon
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, RR
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Simplified 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.
Flower colours
Violet/Purple, White
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.
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.
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.
Detailed taxonomy
Genus
Family
Synonyms
Olearia semidentata Decne., Olearia semidentata Decne. var. semidentata, Olearia semidentata var. albiflora Dorrien-Smith, nomen nudum, Eurybia semidentata (Decne.) F.Muell
Endemic taxon
Yes
Endemic genus
Yes
Endemic family
No
Ecology
Flowering
November - March
Fruiting
January - June
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).
Other information
Where To Buy
Not commercially available.
Plant of the Month
This plant has been featured as a Plant of the Month – see Trilepidea: NZPCN newsletter for April 2009 for the full story.
Etymology
semidentata: Partially toothed
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.
MACSEM
Chromosome number
2n = 108
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, RR
2012 | At Risk – Naturally Uncommon | Qualifiers: IE, RR
2009 | At Risk – Naturally Uncommon | Qualifiers: IE
2004 | Range Restricted
Referencing and citations
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
Attribution
Fact Sheet prepared for NZPCN by P.J. de Lange 28 April 2022. Description by P.J. de lange (27 April 2022).
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)