Adding finished compost to your raised beds in fall will help improve your soil's structure, balance its pH, and feed the healthy microorganisms living in your soil. Top dress your beds with a thick layer.
I usually go through and lightly rake my flower beds at least once in the fall and that cuts down on the amount of clean up I have to do in the spring. If you have a problem with rotting perennials or rotting bulbs, it's especially important to get as much leaf debris off your flower beds.
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
Many landscaping professionals actually practice — and prefer — fall mulching. Fall mulch works like spring mulch to retain soil moisture, suppress weed growth and protect bare soil from erosion.
It's important to cut back foliage in the fall to protect flowering plants from disease and give them a clean start for regrowth as winter starts to turn into spring. However, there are some plants you can keep around through the winter since they benefit wildlife and still offer visual interest for your home.
While many gardeners believe that fall cleanup is the only way to go, there are actually several benefits to leaving a majority of cleanup for the spring. Since many animals and insects are adapted to use plants for winter survival, it makes for a healthier garden to keep their needs in mind.
Unlike perennials, annuals do not come back from season to season so there is no reason to leave these in the ground. Pull them up, roots and all, and add them to your compost pile. Remove weeds and leaf debris. These are common places for diseases and pests over winter.
When To Clean Up The Garden In The Fall. The best time to start your fall garden preparation is after the first few freezing nights have killed back much of the flowers and foliage on the plants. Of course, you can start earlier than that if you want to. But be careful starting too early.
When To Stop Watering Plants in Fall. When the air and soil temperatures consistently fall below 40 F, it's time to stop watering. The ground can't absorb water once the top few inches freeze. Continue to water your plants up until this point so they're as well-hydrated as possible going into winter.
When to Cut Back Hostas. As a general rule, hostas should be cut back in the late fall. Start with leaves that have wilted or turned brown. Healthy leaves can stay a bit longer to help the roots store needed energy.
The Pros of Mulch:
Mulch keeps rain from washing away your soil. As it decomposes over time, bark mulch adds nutrients to your soil. And, maybe everybody's favorite mulch benefit: it discourages weeds from popping up, keeping everything dark so the weed seeds can't sprout.
Obviously, mulch is good at stabilizing soil temperatures which is important as colder weather sets in. It is also good for holding moisture and reducing weeds around the base of the trees and shrubs. Aesthetically, mulch gives your landscape a finished look that distinguishes it during all seasons of the year.
Most perennials will pop through the mulch in spring. If the plants are young, small, or newly planted in fall, you may need to clear some of the mulch in spring so that the plants can emerge without difficulty through the winter protection.
Leave Leaves for Wildlife
Fallen leaves also provide wildlife, especially pollinators, with some winter cover. Bees, moths, butterflies, snails, spiders, and dozens of arthropods and pollinators overwinter in dead plant material for protection from cold weather and predators.
The best time to redo a garden is when you have the time to dedicate to it. That being said, both you and your plants will have an easier time if you do this during the cooler temperatures of early spring or fall. The soil temperatures are likewise cooler and help plants to adjust better.
Even if you haven't been building a compost pile, you still can till in old plant matter that will break down over winter to nourish your soil. Simply run your tiller over your garden plot to blend in the roots of the summer crops you've harvested.
Any gardening expert will tell you, (contrary to what you may believe) that pruning encourages new growth just when the plant is trying to go dormant and new growth doesn't have enough time to harden before the first frost and freezing temperatures hit. Pruning at this time of year will severely weaken the plants.