Forcing Shiitake Mushroom Logs to Fruit

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Growing and producing shiitake mushrooms at home is a practice in patience. Typically it takes a year or two after inoculating freshly cut white oak logs with shiitake mushroom spawn to see your first flush of mushrooms. Seasonal changes in temperature and moisture will cause fruiting to occur naturally in a log that has been fully colonized by the fungus. One clue your shiitake spawn run is finished is to look on the cut ends of the inoculated log for white or brown fungal growth. It is important to wait at least one year after inoculation and 6 weeks following a natural fruiting event before attempting to force fruiting. “Force Fruiting” is simply the process of creating environmental conditions that trigger the shiitake fungus into producing mushrooms aka fruit.

How to Force Fruiting and What to Look For:

  • Soak log in water for 24 hours, but not past 48 hours


    Soak Logs in Water for 24 hours

  • Place log in the shade with high humidity and scout regularly for mushroom primordia. You will see the primordia forming approximately 3 days after soaking.

    Primordia Forming on Log

    Shiitake Primordia

  • Approximately 12 days after soaking the logs should be ready for harvest. Harvest your shiitake mushrooms when you can clearly see “gills” underneath the cap, and the outer cap edge is slightly curled. Use a knife to cut the mushroom off at the stalk.
Shiitake Mushrooms

Shiitake Mushrooms Ready for Harvest

It is important to know that the crop following the first year after inoculation will be light and you can expect the best fruiting to occur 2 to 3 years in. Let a log rest 8 weeks after forcing and force fruiting no more than 3X a year. A log will fruit for the same number of years of the logs diameter in inches. See this publication for more information on producing shiitake mushrooms.

Places to Purchase Shiitake Spawn

Written By

Karen Blaedow, N.C. Cooperative ExtensionKaren BlaedowExtension Agent, Agriculture - Vegetable and Small Fruit Call Karen E-mail Karen N.C. Cooperative Extension, Henderson County Center
Updated on May 18, 2020
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