To store fresh shiitake mushrooms, line a poly or product bag with a dry paper towel, add the mushrooms and keep it slightly open to allow air to circulate. They should stay fresh for as long as two weeks when kept cold. Check to ensure they aren’t moldy each time you want to use them. 

To store dried shiitake mushrooms, make sure they are fully dry and add to an airtight container. Keep in a cool, dry place for up to six months, like your fridge or climate-controlled pantry.