Knee high by the Fourth of July

From the picker's viewpoint 'In high cotton' meant he/ she didn't have to stoop so low, the cotton bolls were thick on the stalk and easy pickin's. Used to indicate that times were good.
Conversely, to be in 'Low cotton', stalks, usually in the hill country, were less than two- three feet high and bolls were sparce making the picker work much harder. i.e. 'I'm in low cotton' meant things weren't going well, didn't feel good, etc.

"Summertime
And the livin' is easy.
Fish are jumpin'
And the cotton is high..."
(Gershwin)

Gotta be the Janis Joplin version (Big Brother & the Holding Company).
Only the best will do.

Midwest US corn farmers have an expression 'knee high by the fourth of July'. A crop which is expected to turn out well will be at least knee high in early July -- which means the initial growing conditions have been good. If a crop doesn't get off to as good start it will not turn out well.