Shiitake (Lentinula Edodes) 

Shiitake is one of the most-cultivated species of edible mushrooms worldwide, and often constitutes the greatest volume of all mushrooms produced globally. China produces the vast majority of shiitake worldwide, while production in the US is relatively low compared to Asian countries. Shiitake cultivation was referenced in China as early as the 12th century, but larger-scale production did not begin until the mid-1940s in Japan, beginning the country’s association with shiitake culture.

Biology:  Shiitake is native to east Asia and naturally occurs as a saprotrophic, white rot fungus of the wood of broadleaf trees. The species has a natural affinity for the wood of chinquapin (Castanopsis) species and other genera of the Beech (Fagaceae) family from which the common name is derived. The name “shiitake” (pronounced shee-tah-keh) comes from Japanese word consisting of chinquapin or shii (椎)and take (茸) which denotes it as a mushroom of the wood of that tree species.

Mycelial growth of the shiitake fungus occurs between 5-32°C but this varies by strain; optimal growth generally falls between 22-27°C. Temperatures above 35°C, can be damaging or lethal; likewise, shiitake growth has been observed to cease when moisture content of its substrate falls below 24% (fresh weight basis). Optimal substrate moisture content for shiitake growth generally falls between 40-48%, after which growth rates begin to be attenuated in accordance with moisture levels restricting gas exchange otherwise needed for metabolic processes. Shiitake requires low levels of light to fruit, although mushrooms will grow without light once fruiting begins. Shiitake’s natural fruiting pattern is autumn and spring-oriented.

Fruiting is primarily induced by shifts in temperature and wetting-drying cycles; this is one of the key biological characteristics that has allowed shiitake to become a widely cultivated species. Fruiting may occur anywhere between 5-25°C depending on strain, but generally occurs within a range of 10°C for a given strain. Strains developed for fruiting in warmer temperatures tend to be more aggressive decomposers and dependent on pronounced shifts in temperature and wetting-drying cycles to induce fruiting. More recently  studies have substantiated observations that shiitake fruiting can also be positively affected by agitating the colonized substrate with physical force or electricity.

Production considerations: Shiitake is an adaptable species that has been developed to yield well and produce reliably. Strains have been developed to produce in different types of production systems with defined production metrics that help make mushroom yield and quality control more predictable. Nonetheless, shiitake strain development is constrained by a lengthy timeline and investment, and are often controlled by industry and/or governmental policy. This aspect can make strain access challenging for growers, and make the strain development timeline asynchronous with the response timeline desired by growers to meet their current needs.