I recently received a question from someone who was a bit confused over which lettuce standard applied to which type of lettuce.  The confusion arises out of the many lettuce standards that are available.

The Boston or Butter lettuces are inspected using the US Grade Standards for Lettuce.  This standard also applies to head lettuce, cello wrapped or naked.        US Grade Standards for Lettuce

The Leaf Lettuces, for Red Leaf Lettuce and Green Leaf Lettuce you would use the US Grade Standards for Field Grown Leaf Lettuce.  This standard is a relative newcomer, being established in 2006.
US Grade Standards for Field Grown Leaf Lettuce

Romaine lettuce also has its own standard.    This standard does provide tolerances for defects, but offers very few scoring guidleines when determining if a defect is “damage,” “serious damage,” or if it is even a defect.  US Grade Standards for Romaine

The final standard for all the field grown lettuces, is the standard for Endive and Escarole.  This standard looks to be the oldest, as it has not been updated for 45 years, being created in 1964.
US Grade Standards for Endive and Escarole