Somewhere in the deepest, darkest recesses of my mind there lurk a few fragments of a song from the sixties, possible recorded by The New Christy Minstrels or another outfit of that ilk and called (I think) 'When Peaches Grow On Apple Trees'.
In it the singer details this horticultural phenomenon along with other highly unlikely occurrences as being more likely than his returning to his unfaithful lover once he has left.

Part of it went:

So wave, wave goodbye to me,
There's many a mountain I've yet to climb,
And anyone who waits for me
Will have to wait a long, long time...

'til peaches grow on apple trees...etc.....

There is also mention of 'when all the mighty oceans freeze', another unlikely occurrence.

This song may be a distant relation of the ones mentioned here.

Then again, it may not.