Mycoscout The short answer
Check the pores and the net. A porcini (Boletus edulis; penny bun in the UK, king bolete in the US) has pores that start white and stuffed, then turn yellow to olive, and do not change when bruised. Its stem is pale cream with a fine white net, clearest near the top. A bitter bolete (Tylopilus felleus) has pores that start white and turn pink, bruise brownish, and a brown net on a tan stem. The flesh of both is white and unchanging when cut, so cutting does not separate them; the pore colour on a mature cap and the net colour do. First Nature calls the bitter bolete "extremely bitter indeed", and MDC warns it can be extremely bitter.
The limit: young bitter boletes still have pale pores, and a dirty stem hides the net. Check pore color on a mature cap, net color and the host trees, and keep any bolete with red pores or bluing flesh out of the basket. Not one of these alone.
Side by side
| Feature | Porcini (penny bun) | Bitter bolete |
|---|---|---|
| Cap | 10–30 cm (First Nature); 8–25 cm (Woodland Trust); yellow-brown to red-brown, greasy, like a bread roll; paler margin | 6–12 cm, up to 18 (First Nature); 5–13 cm (Kuo); 2–6 in (MDC); mid to tan brown, velvety when young, sticky when wet |
| Underside | Pores white and stuffed when young, then yellow to greenish olive; no change on bruising | Pores pale cream then pink to coral pink; 1–2 per mm; bruise brown |
| Stem and base | 10–20 cm tall, up to 10 cm thick, swollen; cream with a white net, strongest at the top | 4–10 cm, 1.5–4 cm thick, often curved, thicker at the base; brown wide-meshed net, strongest on the upper third |
| Flesh when cut | White, no bluing | White, no color change |
| Taste and smell | Mild, nutty; faint pleasant smell | Very bitter; smell not distinctive |
| Spore print | Olive-brown | Clay-pink (First Nature); brownish pink (Kuo); burgundy brown (MDC) |
| Habitat | Mycorrhizal with beech, birch, oak, pine, spruce | Mycorrhizal; oak and beech in the UK, conifers in eastern North America |
| Season | June to October (UK); summer and fall | August to November (UK); June to November (Missouri) |
| Range | Europe; whether true B. edulis occurs in North America is debated, with a complex of similar species | Europe; east of the Rockies in North America (Kuo doubts North American collections are the same species) |
Features that do not separate them
- A brown cap with a net on the stem. Both have one. The net's color is the tell, not its presence.
- White pores. Young specimens of both have white pores. Give a bitter bolete a day and the pink shows.
- White flesh that stays white. Both. Bluing flesh points to other boletes, not to this pair.
- Habitat. Both grow under oak and beech in the UK. In North America the bitter bolete leans to conifers; so do many king bolete relatives.
- "Boletes are never deadly" and other blanket rules. First Nature says none of the porcini's close look-alikes is poisonous, but the same site calls the devil's bolete seriously poisonous, with diarrhea, stomach pain and sickness. The Woodland Trust lists the devil's bolete with its bright red stem as poisonous and rare. A rule about a whole family is not a test for the one in your hand.
- Taste on its own. Experienced foragers use a nibble-and-spit taste test on boletes already confirmed to have no red pores and no bluing flesh. We do not recommend it to beginners: never taste a mushroom you have not identified, and a mild taste proves nothing.
What happens if you get it wrong
The bitter bolete is inedible rather than poisonous in every source we read. MDC lists it as "not edible" and says it can be extremely bitter; First Nature says drying it as a pepper substitute is the only recorded use. A single one cooked with porcini can make the whole dish inedible. No source reports organ damage.
The real risk in this group is a different mistake: a red-pored bolete taken for a porcini. First Nature says the devil's bolete is especially poisonous raw and reports diarrhea, stomach pains and sickness. Its red pores, red net and slow bluing are nothing like a porcini, but a beginner who learned "brown cap, net on stem, bolete, fine" has no defense. Symptoms that start more than 6 hours after a meal point to an amatoxin species and are a different emergency; call poison control (US 1-800-222-1222; UK NHS 111, or 999 if unwell).
Using an app to check a find
A photo of the underside shows pore color on a mature specimen, and a clean photo of the stem shows the net. It cannot show the taste, and it cannot turn a young white-pored bitter bolete pink. Mycoscout leads with the edibility verdict, shows its confidence, and names the bitter bolete and the red-pored boletes as look-alikes with the checks to make in hand. It is not a clearance to eat. Our guide on how to photograph a mushroom explains the four angles; a local mycological society with the specimen is the most reliable check.
Frequently asked questions
How do you tell a bitter bolete from a porcini?
Look at the pores and the stem net. Bitter bolete pores go from white to pink and bruise brownish; its stem net is brown. Porcini pores go from white to yellow-olive and do not change when bruised; its stem net is white, clearest near the top.
Is the bitter bolete poisonous?
MDC lists it as not edible rather than poisonous, and First Nature calls it inedible. No source we read reports serious poisoning. It is listed here as inedible because the taste makes it worthless and because a bitter bolete in a basket means the pores and nets were not checked.
Are there any deadly boletes?
No bolete in our sources is called deadly. The devil's bolete (Rubroboletus satanas) is called seriously poisonous by First Nature, with red pores, a red net on the stem and flesh that slowly blues; it is rare in Britain and absent from the porcini pattern. Do not treat any blanket bolete rule as a safety test.
Which boletes are poisonous?
First Nature calls the devil's bolete seriously poisonous and reports diarrhea, stomach pain and sickness. Other red-pored, bluing boletes are treated with caution in the sources. The bitter bolete is inedible, not poisonous.
Sources
How we checked this page: the Mycoscout team cross-checked every edibility, toxicity and look-alike statement against the sources below on October 31, 2026. It has not been reviewed by a mycologist.
- Boletus edulis, Cep or Penny Bun Bolete, First Nature. Accessed October 31, 2026.
- Tylopilus felleus, Bitter Bolete, First Nature. Accessed October 31, 2026.
- Bitter Bolete (Tylopilus felleus), Missouri Department of Conservation. Accessed October 31, 2026.
- Tylopilus felleus, MushroomExpert.com (Michael Kuo). Accessed October 31, 2026.
- Boletus edulis, MushroomExpert.com (Michael Kuo). Accessed October 31, 2026.
- Penny bun, Woodland Trust. Accessed October 31, 2026.
- Rubroboletus satanas, Devil's Bolete, First Nature. Accessed October 31, 2026.
