Believe it or not, rocks can actually help fall plots.

It may sound completely unthinkable, but industry people are now promoting this a bit (N. Dougherty is in his video).

The smaller rocks (obviously the larger ones are removed) absorb the sun and heat. They radiate similar to burning coals on a grill ready for cooking.What that does is keep soil temperatures up in the fall going into the evening and night, defending a bit against a frost and allowing continued growth (or continued establishment for a fall-planted perennial).

I know it sounds strange, I sure thought so when I first was hit with the info, but it makes sense.