Metrosideros carminea W.R.B.Oliv.

akakura, carmine rātā, crimson rātā

New Zealand endemic.

Easily grown from rooted pieces. There are a few cultivars available from retail nurseries in New Zealand, although most plants sold are from adult cuttings which grow into shrubs rather than climbers. Metrosideros carminea ‘Carousel’ is a cultivar selected for its variegated foliage.

Naturally occurring in the North Island, from Te Paki south to Taranaki in the west and Mahia Peninsula in the east. Occasionally grown in gardens throughout New Zealand.

• Woody long-climbing vine.
• Leaves ranked on either side of stem and lie in one plane.
• Young branchlets hairy, tinged pinkish-red.
• Juvenile leaves with red-tinged margins.
• Juvenile leaves ± circular.
• Flowers carmine.
• Calyx tube narrower than the fruit (2–3 mm wide).

Long-climbing vine up to 15 m high, at first leafy shoots clinging to substrate with aerial roots (juvenile leaves), then as a branched woody vine in tree canopies or occasionally as a bushy shrub in open sites (adult leaves, flowering and fruiting state).

Bark dark brown to grey, separating into thick, squarish flakes. Climbing vines with few branchlets, young growth softly hairy and tinged pinkish-red at growing points, 4-angled, hairy, becoming hairless with age. Trunks rare, only in free-standing bushy shrubs.

Leaves opposite, ranked on either side of stem and lie in one plane, leathery, circular to broadly ovate (round leaves with rounded tips, broadly ovate leaves with pointed tips). Adult leaves elliptic-oblong to broad-ovate, 15–35 mm long, 8–30 mm wide, dark green above, paler below; juvenile leaves thin, circular to ovate, 10–20 mm long, 7–18 mm wide, finely hairy. Leaf surface flat, softly hairy when young, not puckered, midrib raised, oil glands particularly visible on lower surfaces; margins entire, tinged red when young; leaf stalks ± 1–3 mm long, tinged red when young, softly hairy.

Flower clusters many-flowered, crowded at or near tips of branches, flowers ± 10–15 mm in diam., mature flower stalks ± 5–10 mm long, petals 5, rounded and slightly toothed, carmine, ± 5 × 4 mm; sepals 5, tips free, persistent, stalks and base of flowers and outer surface of sepals hairy; stamens carmine, filaments 10–15 mm long, much longer than the petals. Main flowering period: spring.

Fruit dry, rounded, ± 6–9 mm wide, capsule dome occurring below the persistent calyx tube, calyx tube narrower than the fruit (2–3 mm wide), capsule splits along sides to release seeds.

Superficially similar to M. perforata when young and sterile, but in M. carminea young growth of juveniles is pink- or red-tinged, softly hairy and delicate, the adult leaves have red-tinged margins, and are dark glossy-green, not revolute and the glandular spotting diagnostic of M. perforata is scarcely evident. Juvenile M. albiflora has similar foliage but the new growth is not pink- or red-tinged. In New Zealand, carmine-coloured flowers are unique to M. carminea.

Metrosideros carminea is susceptible to myrtle rust (caused by Austropuccinia psidii) in cultivation and in the wild. The species has received a conservation status of Threatened – Nationally Vulnerable as a precautionary measure due to the presence of myrtle rust in New Zealand. Like all rātā, this species is also heavily browsed by possums (Trichosurus vulpecula) who target adult leaves in preference to juvenile.

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.

• CitSciHub
• Flora of New Zealand Online
• GBIF
• iNaturalist NZ
• NZPCN