Polyporus umbellatus Polyporus umbellatus branches

Common name: Umbrella Polypore.

Description and identifying characteristics: This mushroom has a large central stem that splits into multiple branches. The overall mushroom ranges in width from 10 to 40 cm. (4 to 16 inches). The white central stalk ranges from 2.5 to 8 cm. tall (1 to 3 ½ inches) and 2 to 4 cm. thick (¾ to 1 ½ inches). The central stem branches into smaller stems, which attach to single caps or branch eventually into stems attaching centrally to caps. Individual caps range from 1 to 5 cm. wide (3/8 to 2 inches). They are roughly circular with centrally attached stems. The caps range in color from whitish to pale smoky brown. With age the caps become more irregular at the margins.

The mushroom is a polypore so it has tubes under the cap manifesting as pores when viewed. The pores are white, yellowing with age, and decurrent (running down the stem). The flesh is firm and white. The odor and taste are not distinctive.

Polyporus umbellatus pores

The spore print is white. Microscopically the cylindrical spores are 8 to 10 microns long by 2.5 to 3.5 microns wide. They are smooth and colorless.

These widespread but rare mushrooms are saprotrophic or parasitic on the roots or wood of hardwoods, causing a white rot.

These mushrooms grow from a buried sclerotium (a tuber-like underground blackish knot or knots of fungal tissue that is white inside). The sclerotium overwinters so the mushrooms can be found in the same location year after year. These sclerotia can be quite large.

Polyporus umbellatus sclerotia

In China, the umbrella polypore is cultivated not as an edible, but for the sclerotia which are used in Chinese medicine to treat urinary problems and as a diuretic. The mushrooms are grown on buried logs near appropriate hardwood trees.

Ecology/associated host or habitat: Polyporus umbellatus is parasitic on hardwood trees, especially oak, causing a white rot of the roots or saprophytic on buried wood. These mushrooms are widespread growing throughout the Northern hemisphere but they are relatively rare. 

In the upper Midwest, Polyporus umbellatus grows from May to June, and again in September and October in hardwood forests.

Edibility: This is a choice edible mushroom though it is rare enough that many mushroom hunters have never found this mushroom. The umbrella polypore has a strong mushroom flavor that clearly tastes wild and woodsy. Its flavor is strong enough to be usable in many recipes. As a general rule, to minimize the risk of allergic reactions, it is imperative that all mushrooms, including umbrella polypores, be cooked before consuming. It is recommended to limit your portion size whenever eating a species you’ve never eaten before. It is also advisable not to consume more than one new species of mushroom at the same time.

Look-alikes: All of the other similar polypores have fan-like fronds that are larger than the round caps of the umbrella polypore; the fronds are laterally attached to the central stalk of the look-alikes not centrally attached to the circular caps of the umbrella polypore. None of the look-alikes (Grifola frondosa, Meripilus giganteus, Bondarzewia berkeleyi) are poisonous.

Tips on harvesting: Cut the central stalk about ¼ to ½ inch above the ground. Polyporus umbellatus is particularly attractive to mushroom flies, so be careful that the mushrooms are more or less bug free. If you see a cloud of small flies orbiting above the mushroom, it’s probably thoroughly bug-ridden. In general, mushrooms harvested for the table should have fairly firm flesh.

These mushrooms occur year after year in the same spot, so mark the location in your memory, on a log, or on your GPS. You are likely to find mushrooms at the same location whenever weather conditions allow.

Possible allergic reactions and symptoms: Umbrella polypores are considered to be edible and choice. There are no recorded problems with these mushrooms, so follow the usual rules for consuming wild mushrooms. 

Storage. When fresh, these mushrooms should not be stored in plastic. Fresh mushrooms should be stored in paper bags or wax paper. For long term storage the mushrooms can be partially sautéed then frozen. They can also be dehydrated and stored in air tight containers. Remember to process all foods, including mushrooms, in a state-certified kitchen.

Photos:

Smaller specimens of Polyporus umbellatus Multiple growth path
A large specimen Cracked caps

References:

Lincoff, Gary H. (1981) National Audubon Society Field Guide to North American Mushrooms, Alfred A. Knopf , pp. 482-483, Plates 424, 474.

Kuo, Michael and Methven, Andrew S. (2014) Mushrooms of the Midwest, University of Illinois Press, p 324.

Roberts, Peter and Evans Shelley (2011) The Book of Fungi, University of Chicago Press, p 411.

Kuo, Michael (March 2010), Polyporus umbellatus

Michigan Mushroom Hunters Club, September 2009 Mushroom of the Month