Boletinellus merulioides is an odd mushroom, both in appearance and ecology. The Ash Tree Bolete can be readily identified by its tube surface – which is only a few millimeters thick and looks more like a network of ridges – and by the fact that it fruits under only ash trees. B. merulioides appears under ash because it has a unique symbiotic relationship with a pest of ash trees: the Leafcurl Ash Aphid.1,2 Description The Ash Tree Bolete is a medium to large bolete with an irregular shape, off-center to lateral stipe, and very thin tube surface. The cap is roughly circular, but is often lobed and wavy or even somewhat kidney-shaped when the stipe is close to the edge of the cap. It is mostly convex when newly-formed but becomes flat or even vase-shaped as it ages. On the top, the Ash Tree Bolete is smooth and leathery and … Continue reading #143: Boletinellus merulioides, the Ash Tree Bolete