Butyriboletus subappendiculatus

Butyriboletus subappendiculatus produces a medium-sized basidiocarp with a cap (pileus) up to 8 cm across. The young cap is hemispherical, becoming convex to flat-convex and sometimes slightly depressed with age. Its surface is dry or, in older specimens, faintly viscid, smooth to finely fibrillose or cracked, and coloured from brownish orange or cinnamon to buff or grey buff. The cap flesh does not change colour when bruised, and the margin often retains fragments of the partial veil (appendiculate). The tubes are up to 1 cm long and lemon yellow, maturing to a yellow with a faint olive tint; neither tubes nor pores bruise blue. The stipe measures up to 13 cm long and 5.5 cm thick, initially subspherical or ovoid before becoming club-shaped or cylindrical, often with a rooting base. It is pale yellowish-white to pastel yellow, occasionally discolouring to whitish or brownish, and may bear a zone of pale red to brownish-orange. A fine, concolorous reticulation covers much of the stipe, which likewise remains unchanging when handled. The flesh of the stipe is lemon yellow under the surface and fades to straw or whitish in deeper tissues; it shows no bluing on exposure. …

Butyriboletus subappendiculatus fruits in upper-montane coniferous or mixed forests, most commonly under Norway spruce (Picea abies) or silver fir (Abies alba), on neutral to calcareous soils at elevations of 1,200–1,700 m. Fruiting occurs in midsummer, typically from July through August. In Bulgaria, it is known from the high-elevation woodlands of the Pirin and Rila mountains. More broadly, the species has been recorded wherever its coniferous hosts grow across Europe (Austria, Czech Republic, Germany, Spain, United Kingdom, Greece, France, Italy, Montenegro, Norway, Poland, Serbia, Slovenia and Slovakia) and extending into Turkey. It is considered endangered in the Czech Republic.

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