As frost hits and the growing season winds down there are some things that need to be done to keep your garden fabulous:
Remove and compost annual plants once they die. A bed full of wilty dead coleus is not attractive.
Most of your vegetable plants are annuals, so should be removed and composted. Do not leave old tomato plants, tomatoes and leaves lying around in your garden. Cleanliness matters when it comes to preventing disease in your vegetable garden.
In most cases, you should leave perennials as they are over the winter. Their shapes, especially when covered with snow, add some interest to your garden over the winter and seedheads feed birds. Exceptions to this are hostas and herbaceous peonies. Hosta leaves just turn to mush and, at least in my garden, become more of a breeding ground for snails. Herbaceous peony stems and leaves, once the plant has been hit by a hard frost, should be removed and placed in city compost (not your own) as they can develop disease. Note, this advice is for herbaceous peonies only—these are the most common peonies, with soft stems that die down to the ground over the winter. If you have a tree peony (i.e. a peony with a woody stem that stays upright even after frost) just leave it be.
Leave your shrubs alone now. Roses do require some special care (“hilling up”) once the ground freezes solid, but it’s too early to do that yet.
Do your best to ensure that your evergreens go into the winter well hydrated. Their needles will transpire moisture all winter. Give them a good long drink just before the ground freezes. Our fall weather is usually quite damp so I don’t usually have to think about this, but if it’s a dry fall it is certainly a concern. I wrap newly planted evergreens in burlap once the ground freezes, but only for the first year or two. After that, they should be able to stand up on their own. Only use burlap—never plastic or tarp or anything else that can’t breathe.
For my cedar hedges I will often loosely wrap each tree with twine, to help hold the branches upright and close to the tree, to protect against heavy snows. On the years when I forget to do this and we have heavy snow I find that the branches (which are quite floppy) bend outward and sometimes break from the weight of the snow. Note: if you wrap your trees like this in fall, make sure you cut off the twine in the spring.
The trees themselves don’t need any care right now. Rake leaves that fall on your lawn and put them on your garden beds (shred them first, if you have the equipment—I’ve heard that a weed whacker in a metal garbage pail works well, although the process is very noisy). This feeds the soil and helps to insulate the roots of perennials and shrubs. I have been known to collect the leaves my neighbours so kindly rake and place in brown paper bags at the ends of their driveways. One caveat: I am careful not to collect leaves from houses that have black walnut trees—the leaves contain a substance that inhibits the growth of other plants.