Tuberous Polypore

(Polyporus tuberaster)

Conservation Status
Tuberous Polypore
Photo by Honey Fae (Farah)
  IUCN Red List

not listed


not listed


not listed


Tuberous Polypore is an uncommon bracket fungus. From a distance it can be mistaken for a gilled mushroom. It occurs in Europe, western Asia, Japan, and the Americas. It occurs across the United States where it is most abundant but not common west of the Rocky Mountains, and is widely scattered and uncommon elsewhere. It is uncommon in Minnesota. It is found in the spring and fall in deciduous and mixed woodlands. It grows on the ground, on wood, and on wood buried in the ground. When on the ground it often appears in groups of two or three. When on wood it usually appears alone.

When it first appears, the cap is convex when viewed from the side and round, not bracket-shaped, when viewed from above. The upper surface is dry and tan to brown or yellowish-brown. The margins are curved under. As it ages it becomes flat with a depressed center or with a raised bump in the center (umbonate). The mature cap is 1½ to 6 (4 to 15 cm) in diameter, 316 to (5 to 10 mm) thick, funnel-shaped, and darker, sometimes dark orangish-brown. The upper surface is covered with dark fibers (fibrils) and scales. The scales often have erect tips. The margins are sometimes curved upward and are often indented or lobed.

The stalk is solid, tough, 1 to 4 (2.5 to 10 cm) long, and to 1 (1 to 2.5 cm) thick, sometimes thicker. It may be attached centrally, off-centered, or sometimes at one side.

When growing on the ground it is attached to a large underground sclerotium-like tuber. When on wood it sometimes has a connection through the wood to an underground tuber. A sclerotium is a hard mass of mycelium that contains food reserves and can remain dormant for long periods. The sclerotium of one mushroom was used by American Indians as a food source. The sclerotium-like tuber of Tuberous Polypore also stores food reserves, but it contains sand and dirt and is not edible. It is dark brown to black and is irregularly shaped.

The pore surface is white to pale tan. There are 1 to 3 pores per millimeter. The tubes are 132to (1 to 3 mm) long. The pore surface usually runs down the stalk.

The flesh is pale and thin. It is edible when young and fresh after being thoroughly cooked. On older specimens the flesh is hard, tough, and inedible.

The spore print is white.


Similar Species

Habitat and Hosts





Spring and fall


Distribution Map



4, 24, 26, 29, 30, 77.




Uncommon in Minnesota

  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Division Basidiomycota (club fungi)  
  Subdivision Agaricomycotina (jelly fungi, yeasts, and mushrooms)  
  Class Agaricomycetes (mushrooms, bracket fungi, puffballs, and allies)  
  Subclass Agaricomycetidae  
  Order Polyporales (shelf fungi)  
  Family Polyporaceae (bracket fungi)  
  Genus Polyporus  



Boletus tuberaster

Favolus boucheanus

Melanopus coronatus

Polyporellus tuberaster

Polyporus boucheanus

Polyporus coronatus

Polyporus floccipes

Polyporus forquignonii

Polyporus lentus


Common Names


Stone Fungus

Tuberous Polypore












On mushrooms, having a distinct, raised, knob-like projection in the center of the cap.





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Honey Fae (Farah)

    Tuberous Polypore   Tuberous Polypore  








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Other Videos
  Polyporus tuberaster - Tuberous Polypore
The wonderful world of mycology

Jun 14, 2022

I have already uploaded a video of this species, but in April I found a very nice sprout on a possibly oak trunk and was able to track the growth of this fungus. One of the first to grow in spring and that I see with some frequency. It is not poisonous but its leathery meat takes away all the culinary possibilities

I also share the images of some horses with their foals on a sunny day, where suddenly the fog was made. It is what the mountain has, even with fog it gives us these images to enjoy the day.

- Cap: Up to 10 cm in diameter, depressed circular shape, whitish to ochraceous in color, with the surface covered with dark-colored scales. The margin is thin and a little jumbled
-Tubes: Short up to about 4 mm in length, whitish in color
- Pores: Elongated, angular, greater than 1 mm, whitish in color
- Stem: Central, straight or curved at the base on occasions, where we can see decurrent pores and at the end of the foot we can see hairs
- Flesh: Soft, elastic and leathery in adult specimens, whitish in color and with a pleasant smell and taste.
- Habitat: on dead deciduous wood, such as stumps, branches, mainly in oaks and beeches
- Season: Mainly in spring and autumn
- Edibility: It is not toxic, but its meat is coriaceous and therefore it is not usually eaten.

  Polyporus tuberaster (Tuberous Polypore)
Find In Nature - mycology, fungi

Dec 7, 2020

Found 7 mushrooms of Tuberous Polypore (Polyporus tuberaster) growing on wood. Some authors refer bigger spores for Polyporus lentus over Polyporus tuberaster, and that, while the former grow on wood without a sclerotium, the latter grow on the ground and from a sclerotium. The mushrooms that I found were growing on wood and have spores that go up to 19 µm. So, in that sense it would be Polyporus lentus.

However, I think that currently P.lentus and P.tuberaster are considered to be synonyms. Moreover, back in 2018, in that same place, I found 2 specimens on the ground growing from what seemed to be its sclerotium, which reinforces the idea that lentus and tuberaster are the same species.

Sclerotium is an underground blackish potato-like tuber from which the mushrooms emerge, that is thought to be a resting stage structure, used for storage of essential food substances necessary for the fungi to survive harsh periods.

Polyporus lentus is also synonimized with Polyporus forquignonii. Polyporus tuberaster is edible when specimens are very young.




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  Honey Fae (Farah)

Location: Hennepin County

Tuberous Polypore







Created: 12/7/2022

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