Mycena overholtsii produces some of the largest mushrooms of the genus Mycena.
They have caps that are 1.5 to 5 cm (0.6 to 2.0 in) in diameter, and convex in shape, developing an umbo (a central protrusion resembling a nipple) in maturity.
The cap surface is smooth, moist, and marked with radial striations.
The caps are somewhat hygrophanous, and depending on age and state of hydration, range in color from brown or grayish-brown, to dark or bluish-gray.
The mushroom flesh is thin and watery, with a light gray color.

The gills have an adnate, adnexed, or shallowly decurrent attachment to the stem, and are initially closely spaced before becoming well-spaced at maturity.
They have a whitish to pale gray color, and will stain gray when they are bruised.
There are three or four tiers of lamellulae (short gills that do not extend fully from the cap margin to the stem) interspersed between the gills.
The stem is 4 to 15 cm (1.6 to 5.9 in) long by 0.3 to 1 cm (0.1 to 0.4 in) thick, and tapers upward so that the stem apex is slightly thinner than the base.
It can be straight or curved, has cartilage-like flesh, and is hollow in maturity.
When growing on soft, well-decayed wood, the stem often penetrates deeply into the substrate.
The stem is pinkish-brown in color, and the lower half is tomentose – densely covered with white, woolly hairs.
The mushroom has a yeast-like odor and a mild taste; its edibility is unknown, but it is not considered poisonous.
Mycena overholtsii produces some of the largest mushrooms of the genus Mycena. They have caps that are 1.5 to 5 cm (0.6 to 2.0 in) in diameter, and convex in shape, developing an umbo (a central protrusion resembling a nipple) in maturity. The cap surface is smooth, moist, and marked with radial striations. The caps are somewhat hygrophanous, and depending on age and state of hydration, range in color from brown or grayish-brown, to dark or bluish-gray. The mushroom flesh is thin and watery, with a light gray color.
The gills have an adnate, adnexed, or shallowly decurrent attachment to the stem, and are initially closely spaced before becoming well-spaced at maturity. They have a whitish to pale gray color, and will stain gray when they are bruised. There are three or four tiers of lamellulae (short gills that do not extend fully from the cap margin to the stem) interspersed between the gills. The stem is 4 to 15 cm (1.6 to 5.9 in) long by 0.3 to 1 cm (0.1 to 0.4 in) thick, and tapers upward so that the stem apex is slightly thinner than the base. It can be straight or curved, has cartilage-like flesh, and is hollow in maturity. When growing on soft, well-decayed wood, the stem often penetrates deeply into the substrate. The stem is pinkish-brown in color, and the lower half is tomentose – densely covered with white, woolly hairs. The mushroom has a yeast-like odor and a mild taste; its edibility is unknown, but it is not considered poisonous.
Mycena overholtsii