Autumn winds, with a winter whisper right behind them,  strip trees of their cover, using it as a marvelous landscape’s colorful paint. So it´s no wonder, that leaves also made their way into colloquial Englisch to brighten it up a little:

to turn over a new leaf = start all over again

Let bygones be bygones let´s turn over a new leaf

a fig leaf = to cover up something shameful

The War on Drugs simply provides a fig leaf for covering up drug traffickers’ dirty practices.

to shake like a leaf = to be very nervous or afraid

Johnny was shaking like a leaf when he had to go to the job interview.