Xerocomellus chrysenteron

What You Should Know

Xerocomellus chrysenteron is a small, edible, wild mushroom in the family Boletaceae.

This well-known bolete features a brown to olive-brown cap that quickly begins to develop a cracked, mosaic-like surface in which pinkish flesh is exposed in the cracks. Other distinguishing features include its small to medium size, its general stature (the stem is usually longer than the cap is wide), its usual-but-not-exclusive preference (in North America, anyway) for hardwoods.

An untidy bolete when mature, and of little culinary interest because of its poor texture. This mushroom can be found in summer and autumn. It is now clear that a complex of species was included under the label 'Red Cracking Bolete' including Xerocomellus truncatus (an American species) and Xerocomellus cisalpinus (which is common throughout most of Europe).

Despite the common name, only a minority of 'Red Cracking Boletes' have caps that crack. (Xerocomellus cisalpinus, in contrast, is very often seen with a red cracked cap!) To separate this rather uncommon bolete from its close lookalikes it is, therefore, essential to check all of the characters listed. This is a difficult bolete to identify with any certainty.

Other names: Red Cracked Bolete,.

Xerocomellus chrysenteron Mushroom Identification

1. Ecology

   Mycorrhizal with hardwoods, especially oaks, and also sometimes reported with conifers; growing alone, scattered, or gregariously; summer and fall, or in winter in warm climates; widely distributed in North America.

2. Cap

   2-7 cm; convex, becoming broadly convex or almost flat; dry; finely velvety when young; becoming cracked in age, usually conspicuously, with reddish to pinkish flesh showing in the cracks, especially towards the margin; brown to olive-brown, or rarely reddish overall, in old age; marginal area often reddish in age.

3. Pore Surface

   Yellow when young, becoming brownish or olive; bruising blue, sometimes slowly; with 1-3 angular pores per mm; tubes to 5 mm deep.

4. Stem

   3-7 cm long; 0.5-1.5 cm thick; more or less equal, or tapering to a pinched base; solid; yellow above, pinkish reddish below; purplish-red at base; basal mycelium white to yellowish; not reticulate, but sometimes with broad longitudinal ridges.

5. Flesh

   Whitish to pale yellow when young, yellow in age; staining slowly bluish on exposure.

6. Chemical Reactions

   Ammonia negative to brownish on cap; negative to brownish on flesh. KOH negative to brown on cap; negative to brownish or orangish on flesh. Iron salts olive on cap; negative on flesh.

7. Spore Print

   Brown to dark olive-brown.

8. Microscopic Features

   Spores 10-14 x 3-4 µ; smooth; subfusiform; golden in KOH. Hymenial cystidia fusoid-ventricose to fusoid; to 45 x 15 µ; yellow in KOH. Pileipellis a tightly packed trichoderm; elements brown in KOH, encrusted, 2.5-5 µ thick; terminal cell often browner and more narrow.

Xerocomellus chrysenteron Look-Alikes

1. Xerocomellus cisalpinus

   Has a yellow stem flushed red in the lower part and blueing when cut or bruised near the stem base; its spores are finely striated.

2. Xerocomellus truncatus

   In the USA a similar bolete, is differentiated from the Red Cracking Bolete only by the microscopic characters of its spores, which as the name suggests are 'truncated'.

3. Pseudoboletus parasiticus

   Ssynonyms Xerocomus parasiticus and Boletus parasiticus has a yellow stem without red fibrils, and it occurs only with the Common Earthball (Scleroderma citrinum) upon which it may be slightly parasitic.

4. Xerocomellus pruinatus

   Which has not cracked cap cuticle, striate spores, and slowly blueing flesh.

Xerocomellus chrysenteron Cooking Notes

This mushroom is considered edible but not desirable due to bland flavor and soft texture.

The pores are recommended to be removed immediately after mushrooms are picked as they rapidly decay.

Young fungi are palatable and suitable for drying, but they become slimy when cooked; mature specimens are rather tasteless and decay quickly.

Xerocomellus chrysenteron Taxonomy and Etymology

This bolete was first described and named in 1789 by the famous French botanist-mycologist Jean Baptiste Francois (Pierre) Bulliard, who initially called it Boletus communis. In 1791 Bulliard changed the specific epithet to chrysenteron, and after various reshuffles of generic/specific name over the succeeding 200 years or so the Red Cracking Bolete is now generally referred to as Xerocomellus chrysenteron, following a 2008 publication by the Czech mycologist Josef Åutara, whose studied in detail morphological character of this and other closely-related boletes - since further supported by DNA studies.

The generic name Boletus comes ​​from the Greek bolos, meaning "lump of clay", while the new genus name Xerocomellus indicates a (rather distant, actually) relationship with the genus Xerocomus. The prefix Xero- means dry.

The specific epithet chrysenteron means 'golden inside' - a reference to the bright yellow flesh of this mushroom.

Xerocomellus chrysenteron Synonyms

1. Boletus chrysenteron Bull. (1789)

2. Xerocomus chrysenteron Quél.

3. Boletus pascuus (Pers.) Krombh.

4. Boletus cupreus Schaeff., 1774

5. Versipellis chrysenteron (Bull.) Quél., 1886

6. Boletus subtomentosus var. cupreus (Schaeff.) Pers., 1800

7. Suillus chrysenteron (Bull.) Kuntze, 1898

Sources:

Photo 1 - Author: Dr. Hans-Günter Wagner (Creative Commons Attribution-Share Alike 2.0 Generic)

Photo 2 - Author: Björn S... (Creative Commons Attribution-Share Alike 2.0 Generic)

Photo 3 - Author: Jörg Hempel (Creative Commons Attribution-Share Alike 2.0 Germany)

Photo 4 - Author: Lukas from London, England (Creative Commons Attribution-Share Alike 2.0 Generic)