Postia stiptica

What You Should Know

Postia stiptica is a white irregular-shaped bracket up to 10 cm across, but often less. 1 to 3 cm thick. Lower (fertile) surface with tubes and pores; watery droplets are exuded mainly from the margin region and the pores. Very bitter taste. It may turn ochre-brown when old. It is inedible.

It has been reported to be a weak pathogen (Niemelä 2016), but is mostly found fruiting in stumps and bases of fallen trees, even on roots. The fruiting bodies are white, pileate, rough on the upper surface, and extremely bitter. The species is common throughout the Northern Hemisphere in coniferous forests.

Other names: Bitter Bracket.

Postia stiptica Mushroom Identification

1. Cap

   Irregular bracket; up to 10cm across; sometimes roughly semicircular but more often shell-shaped and very occasionally in the form of a lopsided spinning top; 1 to 3cm thick; upper (infertile) surface finely velvety, uneven; white, becoming light ochre with age; margins rounded in young specimens, more acute as fruitbodies age; lower (fertile) surface with tubes and pores; watery droplets are exuded mainly from margin region and the pores.

2. Tubes

   The tubes are white and 2 to 6mm deep.

3. Pores

   The tiny pores are also white and spaced at 3 to 4 per mm.

4. Spores

   Elongated ellipsoidal to cylindrical, smooth, 3.5-4.5 x 2-2.5µm; inamyloid.

5. Spore Print

   White.

6. Odor and Taste

   Strong fungal odor; very bitter taste.

7. Similar Species

   Postia caesia is similar but has a blue tinge and lacks the watery droplets associated with the Bitter Bracket.

Postia stiptica Taxonomy and Etymology

Although this fungus was described as early as 1774 by Jacob Christian Schaeffer, who called it Boletus albidus, its basionym dates from 1801, when Christiaan Hendrik Persoon described it and gave it the scientific binomial name Boletus stipticus. Swiss mycologist Walter Jülich transferred this species to its present genus, thereby establishing its currently-accepted name as Postia stiptica.

Synonyms of Postia stiptica include Boletus albidus Schaeff., Boletus stipticus Pers., Polyporus stipticus (Pers.) Fr., Polyporus albidus (Schaeff.) Trog, Leptoporus stipticus (Pers.) Quél., Polystictus albidus (Schaeff.) Cooke, Leptoporus albidus (Schaeff.) Bourdot & Galzin, Bjerkandera colliculosa P. Karst., Tyromyces stipticus (Pers.) Kotl. & Pouzar, and Oligoporus stipticus (Pers.) Gilb. & Ryvarden.

Postia, the genus name, was established by Elias Magnus Fries in honor of the Swedish naturalist Hampus von Post (1822 - 1911).

The specific epithet stiptica is a reference to the stiptic (staunching) characteristic of this bracket fungus, which is purported to stop the bleeding if it is applied to an open wound.

Sources:

Photo 1 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 2 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 3 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 4 - Author: Jerzy Opioła (Creative Commons Attribution-Share Alike 3.0 Unported)