The removal of perennial foliage may be performed in the spring or in the fall.  It is somewhat of an aesthetic preference. It is only necessary to clean up your garden in the fall when fungus or disease is present as you do not wish that to overwinter.  

A sustainable approach to fall clean up is to use the chop and drop method.  Cut perennials back and leave the greens debris in place to break down and provide nutrients and humus where it matters most, in the garden bed. A mulching mower performs the same results on your green debris but make sure you utilize only non-diseased debris.

The benefit of raking gardens clean in the spring vs. the fall is that there is less foliage to remove thus less carbon footprint is left as most of the foliage will have simply withered away over the winter.   Other benefits for leaving foliage up are perennial seed pods look fantastic poking through the snow & feed the birds in the winter (that is if you did not dead head them during the growing season).

Use the attached PDF for quick reference during your fall garden clean up!