The U.S. Department of Agriculture’s Agricultural Marketing Service (AMS) recently published a final notice in the Federal Register revising the U.S. Standards for Grades of Mushrooms. This is the first substantive update to the federal grading standards since being established on July 15, 1966.
The revised Standards take effect Sep. 24, 2026.
American Mushroom Institute (AMI), the national trade association representing U.S. mushroom growers, processors, and marketers, says this update is the result of a six-year effort. AMI first petitioned USDA in April 2020 to modernize the standards, and said the two organizations worked closely from 2020 to 2024 to develop proposed revisions, which AMS published for public comment in April 2026. All public comments received during the 60-day comment period were in support of the proposed changes.
Among the key updates, the standards:
- Permit mixed specialty mushroom packs of white and brown mushrooms, reflecting current retail and marketing practices.
- Establish a first-ever U.S. No. 1 portabella grade, with its own tolerances tailored to portabella mushrooms (including portobella, ports, and giant crimini).
- Separate size and defect-tolerance requirements out of each grade’s criteria and into their own standalone sections of the Standards.
- Revise defect tolerances for both U.S. No. 1 and U.S. No. 2 grades, at shipping point and en route or at destination.
- Recognize open veils as a natural characteristic of mushrooms rather than a defect.
- Clarify mushroom quality definitions and terminology throughout.
“This update reflects years of intense and meaningful conversations and collaboration with USDA to modernize a standard that had not changed since 1966,” said Rachel Roberts, President, AMI. “We are very pleased to see this revision finalized, and we are deeply grateful to the AMI members and USDA staff whose hard work and support made it possible. This is a meaningful step forward for our industry.”
Roberts said the association will now turn to the next phase of this effort: working with USDA to develop an updated inspection guide to support implementation of the revised standards.
The full text of the final notice, published as 91 FR 54845, is available in the Federal Register. The current U.S. Standards for Grades of Mushrooms are maintained by AMS at ams.usda.gov/grades-standards/mushrooms-grades-and-standards.
