Thanks to Mountain Thyme for sending me the lyrics below, from this Malvina Reynolds song, sung by Pete Seeger.
God bless the grass
that grows through the cracks.
They roll the concrete over it
to try to keep it back.
The concrete gets tired of what
it has to do.
So it breaks and cracks
and the grass grows through!
I photographed this patch in the sidewalk concrete on Allen Street yesterday. My favourite sidewalk grass, though, is on Smith Street and runs for about twenty feet, between the subway grates and parallel to edge of the street, and is about a quarter of an inch wide. In summer it is a strip of emerald green that looks a lot like a horizontal painting.
Here's a complete YouTube version by the singer Lemonflower.