The good news is we live in a fairly benign and forgiving garden climate, which gives us latitude on what needs to be accomplished when. Still, to save your garden from what is predicted to be a brutal winter, and for your own mental health next spring when garden tasks are multiplying like baby slugs, here's what needs to be tidied and protected:
-Plants in pots are more vulnerable to cold, wind, drought, and too much rain. So mulch, wrap, drag indoors, into the garage, or under the eaves plants that might freeze or drown. I always bring fragrant-leafed geraniums in to scent the bathroom windowsills in winter, protect borderline succulents from wet and cold by moving their pots up against the house, cut down my gunnera and melianthus and mulch them with their own leaves, and bring aeoniums and other favorite tender succulents indoors to winter by a window.
Prune back really long rose canes so they don't blow around too much - but leave most of the pruning until March 1st. Foliage and stems protects the roses from the cold.
Once a perennial's leaves are transparent or collapsed in a wet heap, go ahead and cut it back so you don't have a pile of muck to deal with in early spring. But perennials that are still upright, like echinacea, some of the grasses, and agastache, attract and nurture birds while giving the garden structure and winter interest.
General garden clean up: Pick up diseased rose leaves, cut back brown lily stems to within a few inches of the ground, clean up rubble or piles of anything that shelter slugs and snails. Rake up pine needles, and enough of the leaves so that they don't form a thick layer to trap water that'll rot plant crowns. And keep pulling weeds until we have a really hard freeze.
But mostly you can let your garden die down naturally, let the decaying plant parts turn to rich mulch, and just let it rest as you take a rest yourself and enjoy the dark, chilly days of deep winter.......
Non-hardy succulents like this beauty need to come indoors for the winter - this one has spent the last two winters on my kitchen windowsill, moving back outdoors in summer.