NZ Myrtaceae Key - Online edition

Metrosideros collina (J.R.Forst. & G.Forst.) A.Gray


Common Names

Pacific rātā

Origin

French Polynesia and the Cook Islands.

Cultivation

Easily propagated from fresh seed. A number of cultivars are available of which M. collina ‘Spring Fire’ and ‘Tahiti’ are the most popular. Not to be confused with plants called M. collina ‘Fiji’ or ‘Fiji Fire’, which are cultivars of M. vitiensis that have been planted rarely in New Zealand.

Distribution

Mainly cultivated in lowland areas of the North Island, with three known vouchered plantings in the South Island.

Distinguishing Features

  • Leaves elliptic to obovate (‘Spring Fire’) or widely elliptic to circular (‘Tahiti’).
  • Leaf tips narrowing abruptly to form a short stiff point as long as wide, often twisted or folded in older or larger leaves.
  • Flower colour (due to stamens) orange-red (e.g. ‘Spring Fire’ and ‘Tahiti’) to dark crimson.
  • Flower cluster stalks, individual flower stalks, base of flowers and outer surface of sepals mostly hairy.
  • Flowers sporadically throughout the year.
  • Calyx tube as wide as fruit.

Habit

Depending on the cultivar, either a shrub ± 1.5 m tall (‘Tahiti’), or a tree up to 15 m tall in cultivation (‘Spring Fire’).

Bark and Stem/Trunk

Bark firm, mostly brown to grey-brown, young growth sometimes red. Branchlets thin and often 4-angled, covered in short, soft hairs when young, becoming hairless with age.

Leaves

Leaves arranged in opposite pairs, each pair being at right angles to the pair below, leathery, elliptic to obovate (‘Spring Fire’) or widely elliptic to circular (‘Tahiti’), upper surface of adult leaves usually dark green, slightly paler below, some cultivars variegated, leaf surface flat, juvenile leaves velvety all over; juvenile leaves of ‘Tahiti’ usually silvery, maturing to grey-green; upper surface and lower surface of adult leaves largely hairless, some with persistent hairs; midrib hardly raised, oil glands not readily visible on either surface; margins entire; tips obtuse to rounded (‘Tahiti’) or narrowing abruptly to form a short stiff point as long as wide and often folded (‘Spring Fire’); stalks ± 5–10 mm long, hairy when young, hairless with age.

Flowers

Flowers in rounded terminal clusters, cluster-branchlets often 3-flowered, or flowers solitary on cluster axis. Flowers ± 8–10 mm in diam., mature flower stalks short to absent, petals 5; sepals 5, tips free, persistent, stalks and base of flowers and outer surface of sepals all with short, silvery-white hairs, stamens usually coral pink to orange-red to crimson, filaments ± 25–30 mm long, much longer than petals. Main flowering period: sporadically throughout the year.

Fruit

Fruit dry, ± 6–7 mm wide, upper part of capsule raised above the calyx tube, calyx tube as wide as fruit, seeds released through open valves.

Similar Species

Smaller-leaved forms of M. collina have been confused with M. kermadecensis, but M. collina differs in that the leaf tips may narrow abruptly to form a short stiff extension as long as wide (mucronulate), which is often twisted or folded in older or larger leaves. Leaves tend to be 30–40 mm wide with stamens 25–30 mm long. In M. kermadecensis, leaf tips are generally rounded (and notched), leaves are no wider than 20 mm and stamens are about 10–20 mm long.

Notes

Metrosideros collina is susceptible to myrtle rust (caused by Austropuccinia psidii).

The traditional circumscription of M. collina had it being the only species of Metrosideros to span multiple archipelagos. DNA analyses have now shown the presence of two distinct groups. Metrosideros collina is now thought to be confined to French Polynesia and the Cook Islands, and the second group, now assigned the name M. vitiensis, occurs in Vanuatu, Fiji and Samoa and has been rarely planted in New Zealand. Furthermore, on Cook Islands at least, high altitude forms have been reported to possess broadly ovate leaves, sometimes being pendulous, and accompanied by densely hairy young growth as opposed to low altitude forms possessing narrower leaves accompanied by less densely hairy young growth.

Metrosideros is a genus of more than 50 species of trees, shrubs and vines, mostly found in the Pacific region. New Zealand is well represented by having 12 endemic species.

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