King bolete identification: Boletus edulis (penny bun, porcini, cep)

How to identify king boletes

The king bolete (Boletus edulis) is a heavy, firm mushroom with a brown, greasy cap like a baked bun, a sponge of tiny pores instead of gills, and a thick, barrel-shaped pale stem with a fine net pattern near the top. The flesh is white and stays white when cut. It grows on the ground with trees, never on wood and never in open grass. The two look-alikes that matter are the bitter bolete, told by its pink pores and dark net, and the red-pored boletes, told by their color.

Confirm these features

• Pores, not gills: a sponge of tiny holes under the cap, white when young, yellow to olive later.
• A pale net (white or cream) on the upper stem, lighter than the stem surface around it.
• Pores and flesh stay the same color when pressed or cut; no blue, no brown, checked again after ten minutes (UBC).
• No pink in the pores, no red or orange anywhere on the pores or stem.
• Growing on soil under trees, not from wood and not in open grass.
• Stem solid and firm; cut it lengthwise to check for maggots, which the sources say are common.

Dangerous look-alikes

Bitter bolete (Tylopilus felleus)

Tell apart: the cap is 6–12 cm, mid to dark brown, and from above looks like a penny bun. Underneath, the pores start cream and turn pinkish, then coral pink with age, and bruise brown. The net on the stem is brown on a paler background, the reverse of the king bolete's pale net on a darker stem. The spore print is clay-pink, not olive-brown, and the taste is "extremely bitter" (First Nature). It grows under oak, beech and other broadleaves, August–November in Britain and June–November in Missouri. Risk: inedible rather than poisonous, but a single one makes a whole dish inedible. See porcini vs bitter bolete.

Devil's bolete (Rubroboletus satanas)

Tell apart: a chalky white to greyish cap, 6–30 cm, over pores that start yellowish and turn orange then red. The stout stem carries a red net on a yellow-orange background, turning all red at the base. Cut flesh blues slowly and fades back. Mature specimens smell unpleasant. It grows on chalk under beech and oak in late summer and autumn, mainly in southern England and continental Europe. Risk: First Nature calls it "seriously poisonous", especially raw: diarrhea, stomach pains and sickness. See the FAQ on deadly boletes.

Other red-pored and blue-staining boletes

Tell apart: UBC lists Rubroboletus eastwoodiae and Neoboletus erythropus in the Pacific Northwest as poisonous species with orange or red pores that usually turn blue or black within about ten minutes of rubbing. The king bolete's pores never do this. Risk: NAMA lists "certain red-pored Boletus" under muscarine poisoning: sweating, salivation, tears, vomiting and diarrhea within 15–30 minutes. Avoid every bolete with red, orange or pink pores.

Brown-capped mushrooms with gills

Tell apart: UBC notes that poisonous Cortinarius species of similar shape and color have "radiating, linear gills rather than pores". Turn the cap over first; if there are gills, it is not a bolete at all. The deadly webcap belongs to this group.

Where and when it grows

King boletes are ectomycorrhizal: they live with the roots of trees and fruit on the ground near them. First Nature names beech and birch, and less often oak, pine, spruce and other conifers in Britain, and rock-rose scrub in southern Europe; UBC gives hemlock, spruce, pine and fir forests in the Pacific Northwest. They do not fruit in open grassland, so a "porcini" in a lawn is something else.

Season is June to October in Britain and Ireland, with Wild Food UK noting a flush about a week after rain from late summer; in North America, summer and fall. In the US, the name "king bolete" is applied to several closely related species, and MushroomExpert keys out 14 edulis-like boletes by features such as cap texture and host tree. Missouri's field guide notes that B. edulis itself does not grow there, which is a reminder that range matters as much as looks.

Before you eat any

First Nature calls the penny bun "one of the finest edible mushrooms", and UBC says king boletes are "edible for most people", adding that a rare few get upset stomachs, vomiting or diarrhea. NAMA lists Boletus edulis among species with reports of reactions when eaten with alcohol. Two practical points from the sources: cut every stem lengthwise, because maggots are common and First Nature says greenish-yellow pores usually mean a maggoty specimen; and rely on the pink pores and dark net to catch a bitter bolete. Confirm your first finds with a local mycological society or an experienced forager.

Using an app to check a find

Boletes photograph well: the pores, the net and the cut flesh are all visible if you shoot them, which is why Mycoscout asks for the cap, the underside, the stem and the habitat rather than one shot from above. It leads with the verdict, shows its confidence and names the bitter bolete and the red-pored species as look-alikes to rule out. It cannot taste bitterness or wait ten minutes for a stain, and it is never a clearance to eat. If you are not sure what you have, our what mushroom is this guide walks through the free options too, starting at Mycoscout.

Frequently asked questions