The other day I came across this article:
And I tried regrowing my lettuce from the stump.
Trial 1: FAIL
Trial 2: HOLY CRAP AMAZING SUCESS! (this photo is from day 4)
I cut off the dried out bottom of the lettuce before placing it in water with the 2nd.
Step 1: cut a small slice off the bottom of a robust head of organic lettuce that you've already enjoyed
Step 2: place it in a small dish of water, water no higher than the main stump part
Step 3: refresh water every day
Step 4: REVEL IN THE MONEY YOU ARE NOT SPENDING ON MORE FOOD!