in Thoreau’s Journal:

There was also the columbine, its leaves still alive and green; and I was pleased to smell the pennyroyal which I had bruised, though this dried up long ago. Each season is thus drawn out and lingers in certain localities, as the birds and insects know very well.

If you penetrate to some warm recess under a cliff in the woods, you will be astonished at the amount of summer life that still flourishes there.