Fall's a great time to get a head-start planting next year's garden. The winter rains and cooler temperatures allow the soil to stay moist longer, meaning you won't have to water your new plants as much as you would if you planted them in the spring.
Also, throughout late fall, winter, and early spring, the plant will be helped by the winter rains, forcing it to rest and redirect its energy to root development. In spring, the plant will already have a healthy developed root-system and will be much bigger than what it would be if planted in the spring.
But before you plant, and regardless of whether you live in sunny Southern California-like me, or a colder climate, the first and possibly most important fall garden task is clean-up; how well you clean up the garden now determines the kind of garden you will have later on.
You may wonder if there's a good reason to clean up other than aesthetics. The answer is yes. Keeping the garden clean is key to reducing insect and disease problems for next year.
Ensure a thorough cleaning job by employing these five chores:
1. Clean up perennial beds and borders.
2. Cut down dead flowers.
3. Dig up and remove diseased plants.
4. Clean up any leaves and stems.
5. If you have a vegetable garden, clean up any fruit and vegetables that have fallen.
Note: Any debris left in the garden over winter can cause diseases to enter the soil and appear in the spring.
After you clean up, and before you plant, it's time to amend (or feed) the soil; healthy soil makes healthy-plants and lots of flowers and fruit. The first step in soil preparation is to till the soil to loosen it up. This will get the weeds and weed seeds out now so that later it will be easier to keep the soil bed weed-free. It's also a good idea to till in the fall because it will dry out and warm up quicker in the spring letting you plant cool-season crops early.
Once the soil is tilled, make sure you feed it with lots of manure and compost so plant roots will grow well. Afterward, top it off with a good layer of mulch.
During the late fall you should also clean up your gardening tools. Have your shears, pruners, and mowers sharpened so you can beat the rush come spring. That way, your tools will be ready with the first burst of spring.