Here are the grades and standards of spinach leaves according to USDA:
Shall consist of spinach leaves of similar varietal characteristics which are relatively clean, well-trimmed, free from coarse stalks, seed stems, seed buds, crowns and roots, sandburs or other kinds of burs, decay, and damage caused by clusters of leaves, wilting, discoloration, freezing, foreign material, disease, insects, mechanical, or other means.
Shall consist of spinach leaves of similar varietal characteristics which are well-trimmed, free from coarse stalks, seed stems, seed buds, crowns and roots, sandburs, or other kinds of burs, decay, and from damage caused by clusters of leaves, wilting, discoloration, freezing, dirt, or other foreign material, disease, insects, mechanical or other means.
Shall consist of spinach leaves of similar varietal characteristics which are well-trimmed, free from coarse stalks, seed stems, seed buds, crowns and roots, sandburs, or other kinds of burs, decay, and from damage caused by clusters of leaves, wilting, discoloration, freezing, dirt or other foreign material, disease, insects, mechanical, or other means.
For detailed standards, please refer to this document:
United States Standards for Grades of Spinach Leaves (Fresh)