Joking Uncle Marvin

My great-uncle Marvin, my mother's uncle, has embraced e-mail like no other 80-something. He loves to send me jokes (usually off-color). This morning's mail included this PG-rated one that made me laugh:

An old man lived alone in the country. He wanted to dig his potato garden but it was very difficult work as the ground was hard. His only son Fred, who used to help him, was in prison. The old man wrote a letter to his son and described his predicament.

Dear Fred,
I am feeling pretty bad because it looks like I won't be able to plant my potato garden this year. I'm just getting too old to be digging up a garden plot. If you were here, all my troubles would be over. I know you would dig the plot for me.
Love, Dad

A few days later the old man received a letter from his son.

Dear Dad,
For heaven's sake Dad, don't dig up that garden, that's where I buried the bodies.
Love, Fred

At 4 am the next morning, FBI agents and local police arrived and dug up the entire area without finding any bodies. They apologized to the old man and left. That same day the old man received another letter from his son.

Dear Dad,
Go ahead and plant the potatoes now. That's the best I could do under the circumstances.
Love, Fred