Pinwheel Mushroom

Marasmius rotula
Thursday, July 7, 2011

This small mushroom, one species among many commonly called the “Pinwheel Mushroom,” can often be found growing in clusters on decaying deciduous wood or leaf litter. They are characterized by small, pale yellowish-brown caps which are tiny—1.5-17 mm in diameter. The caps are convex, having a deep depression in the center and pronounced grooves that radiate from that depression. The stem can be 15-85 mm long, but does not exceed 1 mm in width. The top part of the stem is usually a pale yellow-white to match the cap; the bottom can be light brown. When the mushroom is older, such as in this specimen, most of the stem assumes a blackish-brown appearance. It has no odor or taste to speak of.

The entire genus Marasmius is comprised of tiny mushrooms with thin stems which make their home on leaf litter or woody debris. Mushrooms in this genus play an essential role in the forest ecosystem as decomposers, helping to break down leaf litter and rotting plant debris. Although they are often overlooked, their dried fruiting bodies can be found in leaf litter throughout their range. Another identifying characteristic of mushrooms in the genus Marasmius is their “marcescence,” or ability to revive after dry conditions. When the mushrooms become too dry, they shrivel up and remain hidden in the leaf litter until conditions improve, at which point they resume their previous appearance.

Marasmius rotula can be found across most of North America, generally east of the Rocky Mountains. It thrives in eastern deciduous forests. This specimen was deposited anonymously; others of this same species can be found near Wind Rock and doubtless in other areas near here.



Article by Hazel Galloway.