Boletus leptospermi is an endemic New Zealand bolete strongly associated with Myrtaceae forest (manuka/kanuka) scrub and easily recognised by its mouse-grey to mahogany cap, bright golden-yellow pores, and rapid blue staining of both flesh and tubes.

Cap: 40-80mm diam., convex to plano‑convex. Subtomentose and dry when young, becoming subglabrous to glabrous and sometimes slightly viscid in patches at maturity. Colour mouse‑grey, reddish‑brown, mahogany, or date‑brown, often with yellow patches or streaks; cherry‑red where insect damage exposes context. Cuticle a fragmentary trichoderm when young, becoming a disorganised cutis of repent hyphae with brown contents. Margin entire.
Pores & Tubes: Tubes to 6 mm long, adnate or slightly excavated around stipe apex. Dull yellow when young to bright golden‑yellow at maturity. Pores angular, 0.5-0.75 mm, concolorous with tubes or reddish‑brown in places. Bluing strongly when damaged (a key field character).
Stipe: 30-50 mm x 10-20 mm, equal or slightly bulbous at base. Stuffed to hollow at maturity. Surface subglabrous to finely velutinate from a palisade of caulocystidia; faintly longitudinally striate near apex. Colour yellow to reddish‑yellow, often red‑tinted apically and bright red basally. No ring.
Flesh: Pallid lemon‑yellow, rapidly blueing on exposure. Odour and taste not distinctive.