Clifford D. Simak, 'The Money Tree' (1958).
'Why, Chuck, it's a twenty-dollar bill!'
'Look at that thing on the corner of it.'
She did, with some puzzlement.
'Why, it's a stem,' she cried. 'Just like an apple stem. And it's fastened to the bill.'
Winds up as a kind of cautionary satire about the profit motive / fetishistic miserly greed. For other money trees, see Nalo Hopkinson, Adam Roberts, and Douglas Adams.