I found a photocopy of this poem among some old cookbooks. Googling did not help me find the source, but here it is: 

My Family Tree

I climbed my family tree and found

It was not worth the climb,

And so I scampered down, convinced

It was a waste of time.

Some branches of my family tree

Are rotten to the core,

And all the tree was full of sap,

And hung with nuts galore!

And I though I bragged about my kinfolk

before I made the climb,

The truth compels me now to tell

Of those not worth a dime.

And I beg friends who boast aloud

Of their ancestors great,

"Go climb your family tree and learn

Of crooks who aren't so straight."

I climbed my family tree and learned

as I came sliding down,

My tree is like a 'tater vine:

The best is underground!