I am in zone 5/6. I have never done anything at all to prepare for winter. I have used medium coarse pine bark chips the last 15 years as mulch, but the last 2 years, I have not worked, so no new mulch. I always left the old flower stalks for the birds, left old foliage for extra protection.
I am now "disabled" - man I hate that term! Not in wheelchair, but it is tough for me to get the gardening done. This spring it was SO wet and rainy, I could not get it cleaned up, and did not get pre-emergent down on most of it. On the part that I did I am really noticing a big difference in the amount of weeds!
A woman comes to help when she can. She has worked for 20 years at a big, really well known perennial nursery. She knows her stuff. She tells me to start in Oct. and clean the beds off. Get it all tidied up before winter. We get nice days into December some years.... so that would give me some time. I don't have **that much** area left any more. Her thinking is that if I have perennials that can't make it through the winter without mulch or foliage - I didn't need them anyway. And, she thinks I will have less pests, less disease by cleaning off in fall.
Then, she says, I can get out there first thing in the spring, even when there is a bit of snow on the ground and get that pre-emergent down!
I have daylilies, peonies, phlox, hosta, hellebore, monarda, hardy hibiscus, coneflower, asters, salvias etc. --- your general mixed perennials.
But, I have always been a "spring cleaner".... Been doing it this way 25 years, I am "scared" to change... stuck in a rut...

The idea of getting the pre-emergent on early and on ALL the beds is really appealing to me -- and I am considering following her advice --- but will I lose peonies or other plants?

Is it worth the risk?
What do you folks do that live in the north? Do you clean before winter or in the spring?
This is part of my "main" mixed bed. It is crammed full of plants. When I downsized, I didn't really plan the bed, this is just how it came out! I had a huge bed on a hill in the back of my house. I kept giving away plants over 4 years until I got down to my very favorites. Then, one day my friends came and moved them into this bed which is in the front of my house. In two years, it has really filled in nicely. This was actually taken last year. It is a JUNGLE out there this year! This bed DID get pre-emergent, and I only see weeds along the edge. There may be some in there under all the perennials but they are pretty thick!