Harvest leaf lettuce when the leaves are small and tender. The plant will continue to produce tender leaves even after the first harvest.
Harvest butterhead lettuce when the heads are full, but still young and tender.
Heading lettuce should be picked when the heads are firm and the size reaches 6" to 8" in diameter.
Storage and Preservation Methods
Use fresh. Can be stored for a few days in the refrigerator, but should not be allowed to dehydrate.
Make a fresh cut at the bottom of head lettuce and place in a small bowl half filled with water so that the core maintains contact with water. Leaf vegetables are best when served the same day as harvested.