Grifola frondosa (Dicks.) Gray, is fungal species that produces mushroom fruiting bodies in autumn as temperatures begin to drop at night and fall rains arrive (Sept-Oct). This species is a polypore and belongs to the family Polyporaceae. These mushrooms are found at the base of of living oaks, and sometimes decaying wood. These fungi cause butt rot on oak and are considered weak parasites on belowground tissues of oak and other hardwood species. Once a fruiting structure emerges from the soil it may take up to two weeks or longer to develop and mature. Fruiting bodies can often be collected from the same location annually for many years. Mature fruiting bodies are generally between 10-55cm across and are composed of multiple caps that are branched from a single thick and base or stem that emerges from the soil. Individual caps (fronds) are 2-10 across, fan shaped, and tend to be gray or brown in color. Tips of the caps tend to be lighter in color with wavy margins. The hymenium is white in color, yellowing with age, and poroid, with pores lining the underside of the cap and stem, often right down to the ground. Spore print is white in color. Spores are 5-7 um in length and 3.5-5 um in width, broadly elliptical in shape and inamyloid in Melzer’s solution. Cystidia are absent from the hymenium. The mushroom texture is firm tissue white in color and lacks conspicuous bruising, in contrast to Meripilus species that may be mistaken for Grifola.
Other comments: Grifola frondosa is a popular edible species, commonly known as “hen-of-the-woods” given its appearance in nature. Most people find this mushroom a choice edible, but be sure to cook it thoroughly. This mushroom is cultivated in many countries and is also being researched for its nutritional and medical qualities. For example, current studies are examining Grifola frondosa as a functional food for the treatment or prevention of hyperlipidaemia and atherosclerosis (http://www.readcube.com/articles/10.3389/fmicb.2016.01186). Ongoing research is investigating the immune enhancing properties of these mushrooms (http://atm.amegroups.com/article/view/3394/4245) .
Here are some other studies on the use of Grifola frondosa in cancer and immuno-therepy:
Shomori K, Yamamoto M, Arifuku I, Teramachi K, Ito H. Antitumor effects of a water-soluble extract from Maitake (Grifola frondosa) on human gastric cancer cell lines. Oncol Rep. 2009 Sep;22(3):615-20.
Lin H, de Stanchina E, Zhou XK, et al. Maitake beta-glucan promotes recovery of leukocytes and myeloid cell function in peripheral blood from paclitaxel hematotoxicity. Cancer Immunol Immunother. 2010 Jun;59(6):885-97.
Louie B, Rajamahanty S, Won J, Choudhury M, Konno S. Synergistic potentiation of interferon activity with maitake mushroom d-fraction on bladder cancer cells. BJU Int. 2010 Apr;105(7):1011-5.
Grifola frondosa (Dicks.) Gray, A natural arrangement of British plants 1: 643 (1821) [MB#362177]10.04.16