The mushrooms should be ready to harvest in approximately 3 to 5 days after you see the first mushrooms begin to form. When the cap of the largest mushroom in the cluster begins to go from convex (turning down at the edges) to concave (flattening out or turning up at the edges), pick the whole cluster. Blue oyster and elm oyster mushrooms grow in clusters of multiple mushrooms, and it is generally best to pick the entire cluster when you see that the largest mushrooms in the cluster are ready to harvest. A white powder on the side of the bag means the mushrooms are simply dropping their seeds. This is normal and safe. Harvest your mushrooms right away.
Watch our YouTube video on how to grow and when to harvest your oyster mushrooms at: http://www.youtube.com/watch?v=TFBlmWP1pxU
The best time to harvest the mushrooms is when the mushroom caps are still slightly curled under. If the cap flattens out, harvest right away, as this is an indication that it is preparing to start producing spores. The spores are harmless but indicate that the mushroom is passing its prime. Cut the stem of the mushrooms as close to the block as possible with a clean knife. The mushrooms may mature at different times, so cut them individually when they are ready. A white powder on the side of the bag and/or plate means the mushroom is simply dropping its seeds. This is normal and safe. Harvest your mushrooms right away. If you want to wait to enjoy your harvest, you can store your shiitake for up to a week in a closed paper bag in the refrigerator.