Iodine Bolete

 

Recently in the grounds of the Chateau de Chenonceau I came across a colony of large bolete mushrooms in a little grove of mature oak trees. When I first encountered them it was raining and their caps were very slimy. This made me think they were in the genus Suillus, but they grow under pines, so I was confused. I turned to the Facebook group Champignons du 37 for help, and overnight, I had a sensible suggestion as to what these mushrooms might be. By then, after a second visit, I had picked a specimen, so I had all the information necessary to confirm the mushroom's identity. Below is the suite of characters that all had to fit, or I could not say for certain I had Iodine Bolete Hemileccinum impolitus (Fr. Bolet dépoli). Syn Xerocomellus pruinatus.

• Cap slimy when wet, like suede when dry; brownish (can be light or dark) and covered in fine white fibres when young (may need a loupe to see); hemispherical when young, flattening with age; developing dimples and a lobed edge with age; 5 - 20 cm across.
• Flesh cream, thicker than the tubes and not discolouring blue when cut. 
• Fine (<1 mm diameter) evenly spaced somewhat polygonal pores.
• Tubes pale yellow when young, getting stronger yellow with age.
• Stem rough (covered in tiny scales) and thick (2 - 6 cm across); red blush at the bottom near roots, and sometimes at the top under the cap; no blue discoloration when cut.
• Spores olive brown.
• Strong odour, especially from the stem when cut (described variously as iodine or walnuts).
  
• Associated with broadleaf trees, especially oak, in warm locations.
  

 

 

To reach an identification (or to determine the species, as a mycologist would say) you need every one of these characters. That's why posting a photo snapped on your phone of a mushroom from the top is never going to get you an accurate identification, and why identification apps don't work for fungi. There are half a dozen lookalike species in this case, of which several are species where real confusion is possible.

Iodine Bolete will grow in both calcareous clay and sandy acid soil. It is present although not common throughout Europe. The mushrooms appear in late summer and through the autumn.

For the record, this species is not toxic, but nobody bothers to eat it.