Leptospermum tairawhitiense G.J. Atkins, de Lange & M.A.M. Renner sp. nov. (Myrtaceae) is segregated from L. scoparium J.R. Forst. & G. Forst. (sensu lato). The new species is endemic to Tairāwhiti / East Cape, Te Ika a Māui / North Island of Aotearoa / New Zealand. The new species is genetically distinct from L. scoparium sensu lato, L. hoipolloi L.M.H. Schmid & de Lange, and L. repo de Lange & L.M.H. Schmid, and chemically it is distinguished by having unusually high levels of triketones. Morphologically, Leptospermum tairawhitiense differs from these species in vegetative characters by the shortly and densely branching growth habit; the often suckering growth habit; the patent leaves, arising at 70–90° from the stem; the lamina is narrow-lanceolate, elliptic lanceolate, or rarely narrowly ovate and (3.0–4.8–6.2(–9.0) mm long by (1.0–1.3(–2.1) mm wide and coloured dull green to dark green, red-tinged, ± glaucescent (new growth yellow-green, red-tinged, glaucescent); and in reproductive characters, the flowers are cupped and small in comparison to other species, being 8–14 mm in diameter, with 5(–8) white petals, 5.0–7.0 × 4.6–6.4 mm and 20–32 stamens with white or pink filaments. The capsules of Leptospermum tairawhitiense are up to 6.8 mm wide and 5.5 mm tall when unopened, with exserted valves that comprise half the capsule height in profile, and when opened the valves exceed the capsule rim. A conservation assessment using the New Zealand Threat Classification System is proposed and a revised key to Leptospermum of Aotearoa / New Zealand provided.

Keywords: Aotearoa / New Zealand, Leptospermum, Myrtaceae, new species, taxonomy

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