Common sorrel is a mordant for black, and the leaves picked in summer produce a blue-green dye. Leaves of common sorrel used in salads and sauces, and to remove rust stains from linen. Flowers gathered in August. The flowering tops and an alum mordant give a mustard yellow. Fiddle heads combined with alum mordanted yarn produce a corn yellow.
Young fronds make an olive yellow.
Roots dug in June produce a greyish yellow. Rhizomes made into poultices. Leaves produced bright green, roots made dark blue, grey and black. Roots also made into ink. White pith of j. effusus used as a lamp wick.