Becoming a mushroom forager can be a complicated affair. The existence of different species that to the non-expert appear very alike, makes the attention to minute characteristics important. Failure to correctly identify a certain species can – if you are lucky – result in the consumption of some other edible species, but can also result in the gathering and consumption of unedible or poisonous ones, some deadly poisonous. It is therefore essential to becoming a mushroom forager to know all the characteristics of a certain species as well as those of its look-alikes.

Since different species can be very much alike, having detailed knowledge of the characteristics of all relevant look-alikes, and knowing whether they are edible or not,  is a must. Simply knowing the characteristics of a certain edible species, and having identified it in the field, does not remove the risk of having picked a very similar look-alike. Nor does the knowledge of the characteristics of one or two look-alikes, in case there are more of them. To safely identify a certain edible species, concise information is needed of the characteristics of the relevant species together with the characteristics of the potential look-alikes.

This article seeks to detail all characteristics relevant for the identification of the porcini, or Boletus Edulis, commonly known as porcini, as well as the characteristics of a number of look-alikes, to enable beginner mushroom foragers to distinguish the porcini from potential look-alikes. Thus the article will cover many possible look-alikes, but the confusion of the porcini

Characteristics of the Porcini (Boletus Edulis)

The porcini mushroom, or Boletus Edulis, is part of the Boletus mushroom genus, meaning it is part of a category of more than 100 species all with the name Boletus. Some of the characteristics of the porcini are shared with other members of the Boletus genus as well as with mushrooms of other mushroom genera.

The cap is white when very young, later light reddish brown, though usually a darker brown at the center, and often white at the edge. The association to a crusty brown roll – which in Great Britain has earned it the name penny bun – is quite ap. It is convex, (curved like a half-circle) and sticky under damp conditions. The edge of the cap is often white. Holes in the cap shows, that it is not only humans who like this prized mushroom.

The hymenium of the porcini is the spongy mass of downward-pointing tubes under the cap. This is where the spores – that play a role in dispersal of the species – are produced. This spongy mass of pores is white when the mushroom is young, becoming a greenish yellow with age. They bruise orange-cinnamon to yellow-brown.

The stem is very thick, and ranges in shape from club-formed to centrally bubous. The color varies from whitish cream, especially at the base, to reddish brown, commonly near the cap. On the stem, mostly right under the cap, a white net-like pattern of raised ridges, also called reticulation, can be seen.

Spore color is an important characteristic of mushroom species. It is identified by placing the spore-producing surface, the white/yellow spongy surface under the porcini cap, flat on a white and dark paper. After several hours, (overnight), a sufficient number of mushroom spores have fallen onto the paper showing the color of the spore mass. White and dark paper is used for contrast. The porcini has a brown spore print.

The flesh is white and does not change color when sliced. Its surfaces also do not bruise on handling.

Habitat and season: The porcini is mycorrhizal, meaning it engages in a symbiotic association with certain plants, the roost of which host the fungus. Due to such associations, the porcini is typically found in habitats dominated by pine, spruce, hemlock and fir trees, although it can also be hosted by other trees, such as chestnut, beech and oak.

Poisonous Look-alikes: The devils Bolete and Boletus huronensis. The devils bolete, rubroboletus satanas, has a shape exactly like the porcini. Apart from this similartity, however, the devils bolete should be easily distinguished from the porcini. The most striking characteristic is the stem, dominated by a bright, red color, though it is also typically yellow near the cap and white at the bottom. When sliced, its flesh bruises blue. It is generally regarded poisonous, and symptoms of nausea and violent vomiting has occured, when it has been eaten raw or fried.

Though the false bolete, boletus huronensis, has been reported to have an excellent flavor and no unpleasant after-effects, other reports tell of severe gatrointestinal reactions, and the mushroom may have been involved in a serious of events leading to the the death of an elderly, but heretofore robust, man. The false bolete is distinguishable from the porcini by the typical lack of the net-like pattern found on the latter, as well as an inrolled margin of the cap. It is typically found together with hemlock, and considered an uncommon mushroom in northeastern North America.

Characteristics of the False Bolete (Boletus Huronensis)

As mentioned above, the false bolete, or Boletus huronensis, is described as an uncommon species in northeastern North America. To what extend it grows in other parts of the world is not known to me.

The cap

Like that of the porcini, the cap of the false bolete is brown and quite similar with maggots having left big holes in it. It does tend, however, to be inrolled at the margin.

The hymenium

The false boletus has a spongy mass of pores under the cap just like the porcini. These are yellow, and – contrary to the porcini – they first slowly bruise green-blue, then resolve to red-brown.

The stem

The stem of the false bolete is often white at the upper part with a clear shift in color about midway down, often refered to as a tide mark. The lower part of the stem has a slightly darker, brown or red-brown color, and can have white parts. The false bolete does not have a net on the stem.

Spore color

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Flesh

The flesh is pale yellow and bruises blue.

Habitat and season

The false bolete has a preference for associations with hemlock. 

Characteristics of the Bay Bolete (Imleria Badia)

The bay bolete or Imleria Badia is another edible mushroom with characteristics similar to that of the porcini for which it may therefore be mistaken.

Cap

Both the common name, bay bolete, and the scientific name, Imleria Badia, refer to the reddish brown cap with smaller black parts like the bay horse, (bay brown). Like the porcini, it is also smooth and convex. It is downy when immature, and grows to 5 – 15cm. The cap flesh is white and turns slightly blue when sliced.

Hymenium

The tubes under the cap turn blue when cut and are spaced at 1-2 tubes per mm. The pore surface bruises green-blue when bruised. The color change is sudden and most marked in mature specimens. Touching the pores will leave a blue stain on your hand.

Stem

The stem is mostly brown, covered in fine cottony threads giving it a streaky appearance with the white flesh visible between the brown streaks.

Spore color

The spore print is olivaceous-brown.

Flesh

The flesh of both the cap and stem is whitish, sometimes yellow, turning a red wine color, (vinaceous), beneath the outer cap skin and slightly blue in the region directly above the tubes and in the top of the stem.

Habitat and season

The bay bolete has a symbiotic association, (mycorrhizal), with roots in mixed forests, especially pines and other conifers. The season is late summer to late autumn.

Characteristics of the Bitter Bolete (Tylopilus Felleus)

Except for the rare encounter with the, to some people, poisonous false bolete the bitter bolete embodies the worst experience one should expect, if happening to false identify it as a porcini. As the name implies it is very bitter, and therefore considered inedible. But it is not poisonous. 

Cap

Wehn young the velvety cap is convex and brown, sometimes with an olive tinge. At maturity it becomes a darker shade of brown, flatten, and splits or develops wavy edges.The edge can be white like the porcini. It is typically 6- 12cm in diameter. 

Hymenium

The tubes and pores of the bitter bolete are pale cream at first, turning pinkish with maturity. The tubes are round, densely packed and fairly small. The pallid pores, spaced between 1 and 2 per mm, turn coral pink at maturity.

Stem

The net on the bitter bolete´s stem can be a reason for mistaking it with the porcini. But knowing that the net on the bolete is white on a brown and white stem, whereas the bitter bolete has a quite dark net on a white stem.  

Spore color

The color of the spore print is clay pink.

Flesh

Like the porcini, the flesh is white. It does not bruise. I still in doubt after having sliced it, a taste test should settle the matter. The bitter bolete is, unsurprisingly, quite bitter. 

Habitat and season

The bitter bolete associates with beech, oak and other broad-leaved trees, very occasionally conifers.

The season start at late summer and lasts until late autumn.

Other possible look alikes

The Gyroporus Castaneus is generally considered edible, Though a strain of this mushroom in Portugal has been reported as poisonous. It can be recognized as a mushroom with a hollowing stem, its relatively small size, the splitting of the cap edge and the pale yellow spore print.

The Caloboletus Calopus has got very bright red and yellow colors on the stem, with blue-green staining, and yellow pores. It should therefore not be hard to distinguish from the porcini. It is perfectly edible but much more of a look alike of the Boletus Chrysenteron, or bitter beech bolete, which is also non-poisonous, but very bitter.

For more information www.mushroomexpert.com is an excellent online mushroom source. The research of Ernst E. Both is considered an excellent source of information on the boletus genus. It is also generally advisable to consult various sources for confirmation as well as seeking expert guidance or consultation.