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Grifola frondosa is a polypore mushroom that grows at the base of trees, particularly oaks. Also known as hen-of-the-woods, maitake (舞茸, "dancing mushroom"), ram's head or sheep's head. It is typically found in late summer to early autumn. It is native to China, Europe, and North America.
|pores on hymenium|
|cap is offset or indistinct|
|hymenium is decurrent|
|stipe is bare|
|spore print is white|
|ecology is parasitic|
Like the sulphur shelf mushroom, G. frondosa is a perennial fungus that often grows in the same place for a number of years in succession. It occurs most prolifically in the northeastern regions of the United States, but has been found as far west as Idaho.
G. frondosa grows from an underground tuber-like structure known as a sclerotium, about the size of a potato. The fruiting body, occurring as large as 100 centimetres (40 inches), rarely 150 cm (60 in), is a cluster consisting of multiple grayish-brown caps which are often curled or spoon-shaped, with wavy margins and 2–10 cm (1–4 in) broad. The undersurface of each cap bears about one to three pores per millimeter, with the tubes rarely deeper than 3 mm (1⁄8 in). The milky-white stipe (stalk) has a branchy structure and becomes tough as the mushroom matures.
In Japan, the maitake can grow to more than 45 kilograms (100 pounds), earning this giant mushroom the title "king of mushrooms". 
Some similar-looking species are toxic. Edible species which look similar to Grifola frondosa include Meripilus sumstinei (which stains black), Sparassis spathulata and Laetiporus sulphureus, another edible bracket fungus that is commonly called chicken of the woods or "sulphur shelf".
The species is a choice edible mushroom. Maitake has been consumed for centuries in China and Japan where it is one of the major culinary mushrooms. The mushroom is used in many Japanese dishes, such as nabemono. The softer caps must be thoroughly cooked.
Although under laboratory and preliminary clinical research for many years, particularly for the possible biological effects of its polysaccharides, there are no completed, high-quality clinical studies for Grifola frondosa as of 2019.
- McIlvaine, Charles; Robert K. Macadam; and Robert L. Shaffer. 1973. One Thousand American Fungi. Dover Publications. New York. 729 pp. (Polyporus frondosus, pp. 482-483 & Plate CXXVIII.)
- Meuninck, Jim (2015-06-01). Jim Meuninck - Basic Illustrated Edible and Medicinal Mushrooms, pp. 13-14, Rowman & Littlefield, 1 Jun 2015. ISBN 9781493014682. Retrieved 27 April 2017.
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- Meuninck, Jim (2017). Foraging Mushrooms Oregon: Finding, Identifying, and Preparing Edible Wild Mushrooms. Falcon Guides. p. 114. ISBN 978-1-4930-2669-2.
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- "Maitake, Grifola frondosa". Drugs.com. 2 September 2019. Retrieved 19 December 2019.
- "Maitake". Memorial Sloan Kettering Cancer Center. 2019. Retrieved 19 December 2019.
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