Shaggy-stalked bolete

Description

The shaggy-stalked bolete, known in Poland colloquially as the American bolete, is a North American bolete that has been spreading through Europe for over a decade. It has a matt, reddish-brown cap with an overhanging margin (a "frill"), yellow pores and a very long, yellowish stem covered with deep furrows and a coarse network. The flesh does not turn blue when cut.

It grows under pines on sandy soil, most often on overgrown dunes and heaths. In Poland it appeared first on the coast and today can be found throughout the country, from August to October.

It is easiest to recognise by its tall, shaggy, net-ridged stem and the overhanging cap margin. Beware of the bitter bolete, which also has a reticulate stem but pink pores. If you are not sure of the species, do not pick it.

Identification features

Cap

Diameter 4–20 cm; convex, only partly flattening with age (descriptions differ). Surface dry, matt, velvety when young, finely cracked with age. Colour dark brown to cinnamon in young specimens, later reddish to reddish-brown, sometimes with a grey or olive tint. The cap margin extends beyond the tubes as a characteristic frill.

Hymenophore (underside of the cap)

Tubes 1–2.5 cm long. Pores round, 0.5–2 mm, bright yellow at first, becoming yellow-green to olive-brown with age. They do not bruise blue.

Stem

Long and slender, 7–24 cm long, 1–5 cm thick, cylindrical or widening at the base, solid, dry. Colour yellow, peach or close to the cap colour, somewhat paler. Surface strongly furrowed, with a prominent coarse reticulum, especially on the upper two-thirds; white mycelial felt at the base. In wet weather the base becomes sticky. In stature it resembles a scaber stalk more than a typical bolete.

Flesh

Whitish to pinkish. Does not turn blue when cut; may slowly turn brownish or yellowish (descriptions differ). No distinctive odour, taste acidic.

Spore print and spores

Spore print olive-brown. Spores oval to spindle-shaped, smooth, 18–33 × 7.5–12 µm; among the largest of any North American bolete.

Habitat and distribution

Ecology. Mycorrhizal with Scots pine (Pinus sylvestris) and mountain pine (Pinus mugo); in North America associated with pines. Grows singly, scattered or in groups on sandy soil.

Distribution. Native to North America (from eastern Canada to North Carolina and Michigan, also Mexico). In Europe an alien species: first confirmed finds from the Curonian Spit in Lithuania (2007–2009, published 2011), then Latvia, Estonia, Scandinavia, Finland, Belarus, Ukraine, Germany, and in 2025 Czechia and Slovakia. Recorded in Poland since about 2016, first on the Baltic coast, now throughout the country; most often on pine-covered dunes and heaths. Not legally protected in Poland.

Fruiting. August to October, in mild autumns until November.

What can it be confused with?

• Tylopilus felleus (bitter bolete) — Also has a reticulate stipe, but the network is darker than the background, the pores are whitish then pink, and the flesh is very bitter. Also grows under broadleaved trees.
• Boletus edulis (penny bun) — Stipe thick, barrel-shaped, with a fine white reticulum only in the upper part; pores white, later yellow-green; cap margin without an overhanging frill.
• Leccinum scabrum (birch bolete) — Similarly slender stipe, but covered with dark scales rather than a network; pores whitish to grey; grows under birches.
• Xerocomus subtomentosus (suede bolete) — Smaller, with a shorter stipe without deep reticulation and with large, angular pores.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• In Latvia it was named fungus of the year 2014.
• Its spores, up to 33 µm long, are among the largest of any North American bolete.
• The species has been moved between four genera (Ceriomyces, Boletus, Boletellus, Aureoboletus); its current placement was established by DNA studies in 2015.
• The origin of the European populations was confirmed by comparing DNA sequences of Lithuanian specimens with North American ones.