pod said:Are you asking about lettuce that is growing in ground or a head of lettuce that you purchased and ate the leafy portion?
I grow lettuce in ground and will remove the larger lettuce leaves around the perimeter of the plant. The plant will keep growing.
To thin the lettuce, I will pull up plants that are too close together. I have noticed that when I cut the leaves and throw the roots on the compost, the plants will start growing more leaves.
I have never tried to grow the core from a store purchased head of lettuce.