Hortiboletus engelii

Description

Hortiboletus engelii has a very variable color and can be colored in shades of brown, orange and red. The surface of the cap is velvety matte. The tubes and pores are yellow, bluish by wounds. The flesh is yellow, especially bluish at the top of the fruiting body, and tiny carrot-orange droplets emerge at the base, which is a good hallmark of this species. The fruiting bodies reach a size of up to 8 cm in the diameter of the cap.

This is an edible mushroom of similar qualities as the Boletus edulis.

Common names: Ruby Bolete Mushroom.

Mushroom Identification

1. Cap

   Caps and various shades of brown but noticeably pinkish towards the margin; ranging from 3 to 8 cm across, broadly convex, and then flattening; the surface is dry and finely downy, often cracking into tiny scales with pale flesh showing in the cracks.

2. Flesh

   The flesh is a soft and very pale yellow, with a reddish-purple line just below the cuticle.

3. Cap cuticle

   The cap cuticle is a palisadoderm of heavily incrusted hyphae (like palisades, or walls of aligned pointed wooden stakes that were used as city defenses in ancient times).

4. Tubes and Pores

   The tubes are dull yellow and terminate in bright-yellow pores that become greenish and eventually orange-brown with age. Tubes to stem connection is adnate with a notch or tooth near the stem. Individual tubes are joined to one another and cannot be separated without tearing tubes open.

5. Pores

   When bruised, the angular pores (left) slowly turn blue.

6. Stem

   3 to 7cm long and 4 to 8mm in diameter, cylindrical; bright yellow at the apex, and flushed with tiny red dots or longitudinal striations in the central region, then whitish or yellowish towards the base. The stem flesh is pale yellow near the apex, becoming a deeper yellow and with tiny orange dots near the stem base. (Any blueing is usually slight and restricted to the stem apex.)

7. Spores

   Subellipsoidal to fusiform, smooth; 10-13 x 5-6µm.

8. Spore Print

   Reddish-brown.

9. Odor and Taste

   Not distinctive.

10. Habitat & Ecological Role

    Ectomycorrhizal fungus; it is found growing on soil usually beneath oaks (Quercus species) and occasionally beeches (Fagus).

11. Season

    Early July to the end of September in Britain and Ireland.

Look-Alikes

Worldwide, this is one of a complex of similar species that can be separated only by microscopic analysis (and even then determination can be far from certain). In Britain and on mainland Europe it is most similar to Hortiboletus rubellus (which has a much redder cap when young and fresh) but could also be confused with Rheubarbariboletus armeniacus, a rare species that also has a reddish cap but lacks the red coloring on the stem.

History

Given the name Boletus engelii in a 2001 publication by Czech mycologist Hlaváček, this bolete was transferred to the new genus Hortiboletus by Israeli mycologist Alona Yu. Biketova and Solomon P. Wasser based on recent molecular (DNA) studies that indicated a need for a major revision of the Boletaceae. This resulted in the current scientific name Hortiboletus engelii (Hlaváček) Biketova & Wasser.

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 engelii is in honor of the German mycologist Heinz Engel, who did much pioneering work on boletes in the late 20th century and had given this species the provisional name Xerocomus quercinus.

Synonyms

1. Boletus declivitatum (C. Martín) Watling, Edinb. J. Bot. 61(1): 43 (2004)

2. Boletus engelii Hlaváček, C.C.H. 78: 67 (2001)

3. Boletus subtomentosus subsp. declivitatum C. Martín, Beitr. Kryptfl. Schweiz 2(no. 1): 18 (1904)

4. Xerocomellus engelii (Hlaváček) Šutara, Czech Mycol. 60(1): 49 (2008)

5. Xerocomus declivitatum (C. Martín) Klofac, Öst. Z. Pilzk. 16: 258 (2007)

6. Xerocomus engelii (Hlaváček) Gelardi, Boll. Assoc. Micol. Ecol. Romana 24-25(nos 75-76): 18 (2009) [2008]

Photo sources:

Photo 1 - Author: Andreas Kunze (CC BY-SA 3.0)

Photo 2 - Author: Björn S... (CC BY-SA 2.0)

Photo 3 - Author: Björn S... (CC BY-SA 2.0)

Photo 4 - Author: Björn S... (CC BY-SA 2.0)

Photo 5 - Author: Björn S... (CC BY-SA 2.0)