Xerocomellus chrysenteron

Description
Mushroom Identification
Look-Alikes
History
Synonyms
Video

Description

Xerocomellus chrysenteron, commonly known as the red cracking bolete, is a small edible mushroom found in hardwood and conifer woods in temperate regions. It forms mycorrhizal associations with hardwood trees, particularly beech. These mushrooms have a distinct appearance with brown to olive-brown caps that develop cracks, revealing pinkish flesh beneath. The stems are bright yellow with coral-red fibrils on the lower part, and the stem flesh turns blue when cut. They have large, yellow pores and produce an olive-brown spore print.

While Xerocomellus chrysenteron is edible, it's not highly sought after due to its bland flavor and soft texture. To prepare them, it's recommended to remove the pores immediately after picking, as they tend to decay quickly. Young specimens are suitable for drying but become slimy when cooked, while mature ones are rather tasteless and prone to rapid decay.

This mushroom's distribution spans from early summer to mid-winter, and it's common in some northern temperate regions. It has also been recorded in places like Taiwan and New Zealand. However, it's important to note that it can be infested by the bolete eater fungus (Hypomyces chrysospermus).

Common names: Cracked Cap Bolete, Red Cracked Bolete, Yellow Fleshed Boletus, Netherlands (Roodsteelfluweelboleet).

Mushroom Identification

Cap

The cap ranges from 0.79 to 2.76 inches (2 to 7 cm) in diameter. It starts off convex but can become broadly convex or almost flat as it matures. When young, it has a fine velvety texture and is dry. As it ages, it develops cracks, often with reddish to pinkish flesh showing in the cracks, especially near the edges. The color of the cap can vary from brown to olive brown, occasionally becoming reddish in old age.
Pore Surface

The underside of the cap has a yellow pore surface when young, which turns brownish or olive with age. It can bruise blue, sometimes slowly. There are 1-3 angular pores per mm, and the tubes underneath the pores extend up to 5 mm deep.
Stem

The stem measures 1.18 to 2.76 inches (3 to 7 cm) in length and 0.20 to 0.59 inches (0.5 to 1.5 cm) in thickness. It is mostly straight but may taper slightly towards the base. The stem is solid and has a yellow upper portion and a pinkish reddish lower portion, which can become purplish red at the very base. The basal mycelium is white to yellowish and not reticulate but may have broad longitudinal ridges.
Flesh

The flesh of this mushroom is whitish to pale yellow when young, turning yellow as it matures. It stains slowly bluish when exposed to air.
Odor and Taste

There are no distinctive odors or tastes associated with this mushroom.
Chemical Reactions

When tested with ammonia, the cap may turn brownish, and the flesh may also turn brownish. When tested with KOH, the cap may turn brown, while the flesh may turn brownish or orangish. Iron salts cause the cap to turn olive but have no effect on the flesh.
Spore Print

The spore print of this mushroom is brown to dark olive brown.
Habitat

This mushroom is often found in association with hardwood trees, especially oaks, and sometimes with conifers. It can grow alone, scattered, or in groups during summer and fall, and occasionally in winter in warm climates. It is widely distributed in North America and Europe.
Microscopic Features

The spores are 10-14 x 3-4 µ in size, smooth, subfusiform in shape, and appear golden in KOH. The hymenial cystidia are fusoid-ventricose to fusoid, measuring up to 45 x 15 µ and appear yellow in KOH. The pileipellis, which is the outer layer of the cap, consists of tightly packed elements that appear brown in KOH, with encrusted, 2.5-5 µ thick cells. The terminal cell is often browner and more narrow.

Look-Alikes

Xerocomellus cisalpinus

This mushroom features a yellow stem with a red flush in the lower part, and it turns blue when cut or bruised near the stem base. Its spores have fine striations.
Xerocomellus truncatus

In the USA, a similar bolete species can be distinguished from the Red Cracking Bolete primarily by the microscopic characteristics of its spores. As the name suggests, the spores of Xerocomellus truncatus are 'truncated.'
Pseudoboletus parasiticus

Unlike Xerocomellus cisalpinus, Xerocomus parasiticus, and Boletus parasiticus have yellow stems without red fibrils. They are commonly found in association with the Common Earthball (Scleroderma citrinum), and there's a possibility that they are slightly parasitic on this host.
Xerocomellus pruinatus

This mushroom can be distinguished by its cap, which does not have a cracked cuticle. Additionally, it has spores with striations and flesh that slowly turns blue when cut.

History

This mushroom, originally named Boletus communis in 1789 by the French botanist Jean Baptiste Francois Pierre Bulliard, was later called Boletus chrysenteron in 1791 by the same botanist. In 1888, it was placed in the new genus Xerocomus, keeping the name chrysenteron. In 1985, Marcel Bon brought back the name communis, making it Xerocomus communis. However, recent research suggests it should be called Xerocomellus chrysenteron since 2008.

The name Boletus comes from the Greek word for "lump of clay," and Xerocomellus suggests a distant relation to Xerocomus, with "Xero-" meaning dry. The specific name chrysenteron means 'golden inside' because of its bright yellow flesh.