Grifola frondosa is a parasitic polypore mushroom that grows in clusters at the base of trees. It is especially associated with oaks.

G. frondosa is native to North America, China and the north-eastern part of Japan. In both Chinese and Japanese traditional medicine, it is considered a medical mushroom. It is currently being investigated for its possible health-promoting properties, and scientific studies have linked it to cancer cell death, immune system boosting and blood sugar reduction. Much more research is necessary, however.

G. frondosa is a popular food mushroom, especially in Asia. It is usually young specimens that are eaten, since old specimens can be very tough. G. frondosa is used in a variety of dishes, including soups and stews.

Scientific classification

Names

In English, this mushroom is known under several different names, including:

• Ram’s head
• Sheep’s head
• Hen of the Woods

Using the name Hen of the Woods can cause confusion, since the Laetiporus sulphureus mushroom is known as the Chicken of the Woods.

In Japan, G. frondosa is known as Maitake which means dancing mushroom. This name is commonly utilized by restaurants and grocery stores even outside Japan, so if you for instance purchase G. frondosa in the United States it is more likely to be labelled Maitake than Ram’s head.

In Italian American communities in north-eastern United States, G. frondosa is known as the Signorina mushroom.

The mushroom

G. frondosa is a perennial fungus. It will typically grow in the same spot for a number of years in a row.

Under ground, the fungus has a tuber-like structure (the sclerotium) which can reach the size of a potato.

Above ground, the fruiting body is a cluster of multiple caps. The caps are grayish to brown in colour and tend to be curled or spoon-shaped, with wavy margins. The undersurface of each cap is porous (1-3 pores per milimetre). The tubes rarely extend for more then 3 mm. While each cap normally stays within the 2-7 cm range, the profusion of caps can make the total fruiting body exceed 100 cm in lenght.

The stipe (“stalk”) of the mushroom sports a branchy structure. It is milky-white in color and will become tough as the fungus matures.

Medical properties

Immune system

In 2009, research conducted by the Memorial Sloan-Kettering Cancer Center showed that G. frondosa could stimulate the immune system of breast cancer patients.1

Cancer

In vitro, G. frondosa has been shown to induce apoptosis in various cancer cells. Apotosis is a process of programmed cell death. 2

Blood sugar

Research indicate that G. frondosa might be beneficial for the management of diabetes and related conditions, since it has the capacity of lowering a persons blood sugar level. This hypoglycemic effect is caused by an alpha glucosidase inhibitor present in the mushroom.3