Boletus bicolor

Description

Boletus bicolor is an edible mushroom that grows in eastern North America, China, and Nepal during summer and fall. The cap and stem are red, and the young pore surface is yellow. The pore surface turns blue quickly when touched, but the rest of the mushroom usually does not. It grows in deciduous woodlands in Canada, Florida, Wisconsin, China, and Nepal. It grows under broad-leaved trees like oak and can grow alone or in groups. You can harvest it from June to October and eat it fresh or dried.

Boletus bicolor is a great ingredient to cook with. It has a unique flavor that doesn't get lost in complex dishes and can be mixed with many different foods.

B. bicolor is known to have health benefits, including antioxidant properties and high levels of minerals like magnesium, zinc, and manganese. It also contains low levels of fat, making it beneficial for those on a low-calorie diet or with high blood cholesterol. However, due to taxonomic challenges, it's difficult to explore its specific health benefits. More research is needed to determine precise dosage information, as there are limited controlled medical research studies on this mushroom. B. bicolor is commonly used in traditional medicine in Tanzania due to its medicinal properties.

Common names: Baorangia Bicolor, Two-colored Bolete, Red Bolete, Yellow Bolete, German (Kirschroter Röhrling, Rötender Mediterranröhrling).

Mushroom Identification

1. Cap

   The cap is 1.57 to 6.30 inches (4 to 16 cm) wide and is initially convex but becomes broadly convex or nearly flat with age. It is dry, velvety when young, and has a texture like soft leather when mature. The color is usually deep pinkish red to dark brick red, fading to reddish or pinkish, but sometimes it is evenly bright yellow when young, and it slowly develops red colors while retaining a yellow margin.

2. Pore Surface

   The pore surface is usually slightly running down the stem, and it has 1-2 angular pores per mm when mature. It is bright yellow when young, becoming orangish, then dull olive-yellow or, rarely, reddish. It bruises blue, usually promptly but sometimes slowly, and the tubes are very shallow, 3-8 mm deep.

3. Stem

   The stem is 51.97 to 5.91 inches (5 to 15 cm) long and 0.59 to 1.18 inches (1.5 to 3 cm) thick. It is a little club-shaped when young, becoming more or less equal above a tapered base. It is solid, bald, bright yellow at the apex (and, rarely, over the upper one-third), and red to purplish red below. It does not bruise when handled or sometimes bruises faintly grayish blue to moderately blue when young. The basal mycelium is yellowish to sulfur yellow, and it is not reticulate, or often with a fine red reticulum over the apical 1 cm or so.

4. Flesh

   The flesh of this fungus is pale yellow in the cap and deep yellow in the stem. It turns faintly and erratically pale blue when sliced, especially over the tubes or not bluing, or in rare cases, bluing moderately. The odor is not distinctive or reminiscent of bouillon or curry-like, and the taste is not distinctive or slightly acidic.

5. Spore Print

   Olive brown.

6. Habitat

   Mycorrhizal; growing scattered or gregariously; summer and fall. It is typically found in mixed forests with chestnut, hazel, or holm oak trees, and is more prevalent in the Mediterranean region. It thrives in warm environments.

7. Odor and Taste

   Odor not distinctive, or reminiscent of bouillon, or curry-like; taste not distinctive, or slightly acidic.

8. Chemical Reactions

   Ammonia negative on cap surface (or very rarely flashing faintly purple), negative on flesh. KOH dull orange on cap surface (or very rarely flashing quickly dark blue); dull orange on flesh. Iron salts dark gray to grayish olive on cap surface; gray on flesh.

9. Microscopic Features

   Spores 9-11 x 3.5-5 µ; subfusiform; smooth; hyaline to yellow or golden in KOH; usually ochraceous to brownish in Melzer's, but occasionally very faintly amyloid, especially in young caps, just after being released from the basidia when the tube trama is amyloid. Hymenial cystidia fusoid-ventricose, fusiform, or more or less mucronate; to about 35 x 7.5 µ. Tube trama often amyloid. Pileipellis a collapsing trichoderm of elements 5-12.5 µ wide, hyaline to yellow in KOH, rarely slightly encrusted; terminal cells tubular-cylindric, with rounded or subacute apices, sometimes becoming narrowly cystidioid at maturity.

Look-Alikes

1. Boletus sensibilis

   Differs from the two-colored bolete in that it has an immediate bruising reaction and is poisonous, causing stomach upset if ingested, and in some cases a severe allergic reaction.

2. Boletus miniato-olivaceus

   Has a full yellow stem and slightly lighter cap coloration. It also has a more immediate bruising reaction than the two-colored bolete and the stem is slightly longer in proportion to the cap.

3. Boletus peckii

   Differs from the two-colored bolete by having a smaller average size, a rose red cap that turns almost brown with age, flesh that is paler in color, and a bitter taste.

4. Boletus speciosus

   Differs from the two-colored bolete by having a fully reticulated stem, more brilliant colors, and very narrow cylindrical spores.

5. Boletus bicoloroide

   Very similar to the two-colored bolete, but it has only been found in Michigan and has larger spores. It's also slightly bigger, with a longer stem and cap.

History

This mushroom was first described by an Italian botanist in 1807. An American mycologist later named a similar species in New York, but his naming is considered incorrect. The name "Boletus bicolor" has been used for both the American and European species.

Another species found in Singapore was also incorrectly named "Boletus bicolor." Recent studies have shown that Baorangia bicolor is not closely related to other Boletus mushrooms, and in 2015 it was moved to a different genus.

The name "Boletus bicolor" refers to its two colors, as it has different colors on different parts of the mushroom.

Synonyms

1. Baorangia bicolor

2. Ceriomyces bicolor (Peck) Murrill (1909)

3. Boletus rubellus subsp. bicolor (Peck) Singer (1947)

4. Xerocomus bicolor (Peck) Cetto (1987)

Video

Photo sources:

Photo 1 - Author: Dmitry Brant (CC BY-SA 4.0)

Photo 2 - Author: Huafang (CC BY-SA 3.0)

Photo 3 - Author: Dmitry Brant (CC BY-SA 3.0)

Photo 4 - Author: Dave W (CC BY-SA 3.0)