The Prisoner S Letter

A prisoner in jail receives a letter from his wife:
""Dear Husband, I have decided to plant some lettuce in the back garden.
When is the best time to plant it?""

The prisoner, knowing that the prison guards read all mail, replied:
""Dear Wife, whatever you do, do not touch the back garden. That is where I
hid all the money.""

A week or so later, he received another letter from his wife:
""Dear Husband, You wouldn-t believe what happened: some men came with
shovels to the house, and dug up all the back garden.""

The prisoner wrote another letter back:
""Dear wife, now is the best time to plant the lettuce.""