How is flammulina velutipes cultivated?

Question:its a winter mushroom under the fungi kingdom

Answers:
Commercial growers use sterilized sawdust in plastic bottles. To get the familiar "bean sprout" shape of a small cap and long stipe (stem), growers allow CO2 to build up in the grow rooms causing the deformation. In the wild or in stump cultivation the mushroom is much larger and more conventional looking. Mine bloom in Oct-Nov. here in North Dakota. RScott