Xerocomus ferrugineus

Description
Mushroom Identification

Description

Xerocomus ferrugineus (syn. Boletus Ferrugineus) mushroom has a creamy white-yellow flesh with a thin red line by the skin. Bug holes are often pink. Yellow pores darken with age and often stain blue-green (rarely cinnamon). Deep tubes.

This mushroom is the best separated from the others in the Boletus group based on its non-bluing flesh, its yellow basal mycelium, its association with conifers, and the green reaction of its cap to ammonia.

It is unclear whether North American and European versions of Xerocomus ferrugineus are the same; the subtomentosus species group is in serious need of contemporary study and revision.

"Rusty Iron" to the brownish cap may lean yellowish & often cracks or fissures w/age. (The California version typically has a red-, chestnut-, or liver-brown cap). The stem is most often ridged at the top, sometimes clear & sometimes in a coarse netting pattern – stem decoration is an iffy guide for this one. Prefers conifers, but can sometimes be found with leafy trees. Easy to confuse with Xerocomus tenax and illudens.

Mushroom Identification

Ecology

Mycorrhizal with spruces and other conifers--but also occasionally reported under hardwoods (especially those occurring in mixed conifer-hardwood forests) and shrubs; growing alone, scattered, or gregariously; summer and fall; widely distributed in northern and montane North America; widely distributed in Europe.
Cap

4–9 cm; convex, becoming broadly convex; dry; finely velvety; usually olive-brown to reddish-brown or yellowish-brown, but occasionally entirely olive or nearly green.
Pore Surface

Yellow, becoming olive-yellow with maturity; not bruising, or bruising slowly bluish; pores xerocomoid, 1-2 mm wide; tubes to 10 mm deep.
Stem

3–7 cm long; 1–2 cm thick; equal to slightly club-shaped, with a pinched off base; dry; solid and tough; widely and coarsely ribbed, over the apex or overall; whitish to yellowish or yellow; basal mycelium yellow.
Flesh

Whitish to pale yellowish; not staining when sliced, or turning pinkish in the cap.
Chemical Reactions

Ammonia flashing blue-green on cap, then resolving to reddish-brown; negative on flesh. KOH dark red to black on cap; orangish on flesh. Iron salts negative to gray on cap; negative on flesh.
Spore Print

Olive to olive-brown.
Microscopic Features

Spores 10–13 x 3–4.5 µm; fusiform; smooth; yellowish in KOH. Hymenial cystidia 35–50 x 5–7.5 µm; lageniform; thin-walled; smooth; hyaline in KOH; inconspicuous. Pileipellis a collapsing trichoderm; yellow in KOH; elements 5–7.5 µm wide, smooth; terminal cells cylindric with rounded apices.