A polarising filter helps reduce reflections on reflective surfaces, such as water or leaves. When you are out on a trip to photograph fall colours, it is paramount that you take your polarising filter with. Look at the difference between the photo Karin took, and what I captured. The cameras used are not important - both are impressive cameras and indistinguishable at web resolutions. Focus on the colours and "pop" in the image below.
This image from Karin's camera without polarising filter:
Same moment, but with a polarising filter attached:
PS: I did not change the saturation in post processing. It is clear how the red leaves are way more saturated and more translucent than the photo without a polarising filter.