Stinky dog stinkhorn mushrooms

The dog stinkhorn fungus is a fungus so unusual, it’s worth knowing.

Dog stinkhorn fruiting bodies. Photo credit: Chris Evans, Illinois Wildlife Action Plan, Bugwood.org

Dog stinkhorn fruiting bodies. Photo credit: Chris Evans, Illinois Wildlife Action Plan, Bugwood.org

In early summer to early fall, a strange fungus makes its appearance across Michigan in a number of gardens. Michigan State University Extension horticulture educators and Master Gardener hotlines receive calls from gardeners who have discovered this oddity in their yards and gardens. Those who have discovered this mushroom are baffled.

What they have found is a mushroom that is called the dog stinkhorn or Mutinus caninus. It comes by its common name because of its appearance and how it smells. It looks like a certain doggy part protruding from the soil. Is it possible that Cerberus, the three-headed dog from Hades, is making an appearance? The fetid odor of the mature mushroom has been described as being associated with the contents of a cat litter box.

There are approximately 22 members of this stinkhorn mushroom family with two being found in Michigan. The elegant stinkhorn is found in wooded areas and looks somewhat similar, but the stinking dog is noted for being found in shaded parks and cultivated locations growing in areas covered with woodchips, leaf litter or rich, organic soils.

This mushroom begins life as a tough-skinned “egg” or an oval structure usually not visible above the mulch. This egg is attached to the soil by a white cord. The egg structure splits open and the mushroom begins to grow rapidly. In five or six hours it has grown to 4 to 5 inches tall and about 0.5 inches in diameter. The egg is now visible at the base of the mushroom. Sometimes there are several in the same location.

The mushroom column is yellow or pink, fragile and cylindrical. The orange tip is usually pointed and curved. The tip of the mature dog is covered in gleba, is a slimy, spore-bearing material. This is how the mushroom reproduces. The gleba is a dark olive-brown color and has a foul odor.

The dog attracts insects that will spread the spores. Flies of all sorts and other insects drop by and pick up the sticky spores or ingest them and then fly away to spread the spores to new locations. The dog mushroom discoveries are almost always in July and August.

Smart gardeners will store this information away for next summer when temperatures, humidity and ground moisture are conducive to the appearance of stinking dogs. It will be interesting to know what you are actually looking at instead of being shocked or horrified. A little mushroom knowledge can be a valuable thing.

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