Kunzea robusta

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Species

Kunzea robusta

Etymology

Kunzea: Named after Gustav Kunze (4 October 1793, Leipzig -30 April 1851), 19th century German botanist from Leipzig who was a German professor of zoology, an entomologist with an interest mainly in ferns and orchids
robusta: sturdy

Common Name(s)

Rawirinui, kanuka

Current Threat Status

2018 - Threatened - Nationally Vulnerable

Previous Threat Status

2013 - Not Threatened

Authority

Kunzea robusta de Lange et Toelken

Family

Myrtaceae

Brief Description

Widespread, common tree of North and South Islands. Bark usually basally detached long leathery strips. Branches bearing masses of green leaves and clusters of small white flowers. Branchlets usually copiously covered in silky, appressed hairs. Leaves variable in size (up to 28 mm long), soft to grasp. Flowers borne in 'corymbiform' clusters, white with a red centre. Fruit a small dry capsule 2.2–4.6 × 3.2–5.3 mm.

Flora Category

Vascular - Native

Synonyms

None - first described in 2014

Distribution

Endemic. New Zealand: North and South Islands.

Habitat

Coastal to lowland shrubland, regenerating forest and forest margins, also present in montane forest, ultramafic shrubland and very occasionally present in subalpine shrubland (up to 900 m a.s.l.).

Features

Trees 8–30 m tall. Trunk 1–6, 0.10–1.0 m d.b.h. Bark stringy, or coarsely tessellated, coriaceous, firmly attached above, detaching basally, often hanging semidetached; peeling upwards along trunk in narrow to broad, tabular strips up to 4 m long. Branches initially erect, soon arching outwards and spreading; branchlets numerous, slender; sericeous, indumentum copious, hairs either long or short antrorse-appressed; if long, then weakly flexuose 0.15–0.38 mm long; if short, not flexuose, 0.09–0.15 mm long. In eastern Coromandel Peninsula and coastal East Cape to Mahia Peninsula, branchlet indumentum in mixtures of divergent 0.03–0.08 mm long hairs, and sparse, 0.1–0.2 mm long, antrorse-appressed hairs. In the Rangitikei region, branchlet hairs of seedling and juveniles divergent, short 0.04–0.10 μm long. Leaves sessile to shortly petiolate, light green or dark green above, paler beneath; oblanceolate, broadly oblanceolate, broadly lanceolate, lanceolate to linear-lanceolate, rarely elliptic to obovate; apex subacute to acute, rarely obtuse, rostrate or shortly apiculate, base attenuate to narrowly attenuate; lamina margin initially finely covered with a thin, interrupted band of spreading to antrorse-appressed hairs not or rarely meeting at apex; hairs shedding with age. Lamina of juvenile plants from coastal areas and northern North Island 14.6–28.4 × 1.6–2.5 mm; from inland areas, 3.2–6.3 × 0.7–1.5 mm; adult lamina of plants from coastal areas and northern North Island 4.9–20.1 × 0.9–3.0 mm; from inland areas, 5.8–12.3 × 1.2–2.2. Inflorescence mostly a compact corymbiform to shortly elongate 1–30-flowered botryum up to 60 mm long; extending near end of flowering season as an 4–12-flowered, elongate botryum up to 80 mm long;. Pherophylls deciduous or persistent; squamiform grading into foliose; squamiform pherophylls 0.4–1.2 × 0.3–0.6 mm, broadly to narrowly deltoid or lanceolate, apex acute, subacute to obtuse, margins finely ciliate; foliose pherophylls 6.0–17.9 × 1.1–1.8 mm, elliptic, oblanceolate, broadly lanceolate to lanceolate, apex obtuse, base attenuate; margin densely covered by antrorse-appressed hairs. Pedicels 1.2–5.2 mm long at anthesis. Flower buds pyriform to obconic, apex flat or weakly domed prior to bud burst; calyx valves not meeting. Flowers 4.3–12.0 mm diameter. Hypanthium 2.1–4.1 × 3.0–5.2 mm, broadly obconic to turbinate, sometimes cupular, rim bearing five persistent calyx lobes. Hypanthium surface when fresh faintly ribbed and sparingly dotted with pink or colourless oil glands, these drying dull yellow-brown or brown; either finely pubescent with the ribs and veins conspicuously covered in longer silky, antrorse-appressed hairs, or glabrous; hypanthium similar when dry though with the ribs more strongly defined and clearly leading up to calyx lobes. Calyx lobes 5, coriaceous, 0.52–1.1 × 0.60–1.4 mm, broadly ovate, ovate-truncate to broadly obtuse, glabrate. Receptacle green or pink at anthesis, darkening to crimson after fertilisation. Petals 5–6, 1.5–3.8 × 1.3–3.6 mm, white, rarely pink, orbicular, suborbicular to ovate, apex rounded to obtuse, oil glands colourless. Stamens 15–58 in 2 weakly defined whorls, filaments white. Anthers 0.38–0.63 × 0.18–0.32 mm, ellipsoid to ovoid-ellipsoid or deltoid. Pollen white. Anther connective gland prominent, light pink, salmon pink, yellow to orange when fresh, drying dark orange, orange-brown or dark brown, spheroidal, finely rugulose or papillate. Ovary 5–6 locular. Style 2.0–3.5 mm long at anthesis, white or pinkish-white; stigma broadly capitate, flat, greenish-white or pale pink, flushing red after anthesis. Fruits 2.2–4.6 × 3.2–5.3 mm, maturing greyish white, obconic, broadly obconic to ± turbinate, rarely cupular; hairy, (rarely glabrous). Seeds 0.9–1.1 × 0.35–0.48 mm, oblong, oblong-obovate, oblong-elliptic; testa semi-glossy, orange-brown to dark brown, surface coarsely reticulate.

Similar Taxa

Kunzea robusta is usually a tall tree (up to 30 m tall) inhabiting coastal to montane successional forested habitats; with the adult leaf surfaces glabrous except for the margins and midrib which are more or less finely covered with a thin, often interrupted band of deciduous hairs tending toward glabrate; and with inflorescences that are initially corymbiform, often elongating toward end of flowering season; and bearing foliose and squamiform, mostly deciduous pherophylls .

Flowering

August–June

Main Flower Colour

White

Other Flower Colour

Red / Pink

Fruiting

Jul–May

Propagation Technique

Easily grown from fresh seed. Can be grown with great difficulty from semi-hardwood cuttings.

Threats

Not Threatened.

Chromosome No.

2n = 22

Endemic Taxon

Yes

Endemic Genus

No

Endemic Family

No

Taxonomic notes

Due to website space limitations the description of Kunzea robusta provided here is much abridged from that offered in de Lange (2014). As circumscribed by de Lange (2014) remains a variable species, and that treatment recognises three races which may warrant further study. Kunzea robusta is the most widespread, common New Zealand species, and it is not only highly variable, but readily forms hybrids with other Kunzea in disturbed habitats. Nevertheless, even in hybrid zones branchlet hairs and bark characters will help distinguish this species.

 

References and further reading

de Lange, P.J. 2014: A revision of the New Zealand Kunzea ericoides (Myrtaceae) complex. Phytokeys 40: 185p doi: 10.3897/phytokeys.40.7973.

This page last updated on 12 Dec 2014

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