Hortiboletus rubellus

Description

Hortiboletus rubellus (Xerocomellus rubellus) is a relatively small bolete with scarlet to the raspberry red cap, reddish stem, and yellow pores, occurring largely with oak. Like many boletes, it stains blue when cut or bruised. It is found in deciduous woodland in autumn. There is some question over its edibility, and it is reportedly of poor quality with a taste of soap. Until 2015, the species was known as Boletus rubellus.

Common names: Ruby Bolete.

Mushroom Identification

1. Ecology

   Mycorrhizal with hardwoods (especially oaks); growing alone, scattered, or gregariously, in woods or, frequently, at their edges, in parks and gardens; summer and fall; North American distribution uncertain.

2. Cap

   2.5-5 cm; convex, becoming broadly convex or nearly flat in age; dry; bald or, when young, very finely velvety; bright, dark pinkish-red, fading to pinkish-red or pinkish; becoming finely cracked in maturity.

3. Pore Surface

   Becoming depressed at the stem; yellow at first, becoming dull olive-yellow; bruising promptly blue; 1-3 angular pores per mm; tubes to 7 mm deep.

4. Stem

   3-7 cm long; 4-10 mm thick; tapered to base and sometimes flared at the apex; yellow to bright yellow at apex, pinkish to red below; usually punctate with red points and dots, at least when fresh; not reticulate; basal mycelium pastel yellow when fresh, becoming ivory.

5. Flesh

   Whitish in the cap; yellow to red in the stem; staining slowly and slightly blue when sliced; flesh in stem base with numerous tiny, bright red to carrot orange dots.

6. Odor and Taste

   Not distinctive.

7. Chemical Reactions

   Ammonia negative on cap surface; negative on flesh. KOH dull orange on cap surface; dull orange on flesh. Iron salts gray on cap surface; negative on flesh.

8. Spore Print

   Olive brown.

9. Microscopic Features

   Spores 10-13 x 4-5 µ; subfusoid; smooth; golden in KOH; dull brown in Melzer's. Hymenial cystidia is more or less lageniform; to about 60 x 12.5 µ. Pileipellis a palisadoderm of septate, encrusted elements 10-15 µ wide; terminal cells obnapiform to subglobose; hyaline to faintly ochraceous in KOH; dull brown in Melzer's.

Look-Alikes

1. Hortiboletus engelii

   Similar, but this species starts with a brown cap and fades to red, where as the Ruby Bolete starts red and slowly fades to brown with age.

2. Boletus campestris

   Very similar, and Boletus bicolor is almost identical.

3. Rheubarbariboletus armeniacus

   A rare species that has a similar reddish cap but lacks the red coloring on the stem.

History

Given the name Boletus rubellus in 1836 by Czech mycologist Julius Vincenz von Krombholz (1782 - 1843), this lovely bolete was transferred to the new genus Hortiboletus in 2015 by Italian mycologists Giampaolo Simonini, Alfredo Vizzini, and Matteo Gelard based on recent molecular (DNA) studies that indicated the need for a major revision of the Boletaceae. This resulted in the current scientific name Hortiboletus rubellus (Krombh.) Simonini, Vizzini & Gelardi,

Synonyms of Hortiboletus rubellus include Boletus rubellus Krombh, Xerocomellus rubellus (Krombh.) Šutara, Boletus sanguineus With., Boletus versicolor Rostk., Xerocomus rubellus (Krombh.) Quél., and Xerocomus versicolor (Rostk.) E.-J. Gilbert.

The old generic name Boletus comes ​​from the Greek bolos, meaning 'lump of clay', while in the new genus name the prefix Horti- comes from the Latin noun Hortus, meaning 'garden'; this is a reference to one of the main habitats in which this bolete is commonly found.

The specific epithet rubellus is also Latin and means 'reddish'.

Photo sources:

Photo 1 - Author: Lukas from London, England (CC BY-SA 2.0)

Photo 2 - Author: Björn S. (CC BY-SA 3.0)

Photo 3 - Author: Lukas from London, England (CC BY-SA 2.0)

Photo 4 - Author: walt sturgeon (Mycowalt) (CC BY-SA 3.0)

Photo 5 - Author: Dr. Hans-Günter Wagner (CC BY-SA 2.0)