Tidy Up Those Flower Beds
While you're out planting spring-flowering bulbs, such as daffodils and tulips, clean up debris in the flowerbeds. Deadhead flowers one last time and remove annuals that have finished for the season. Compost the plant debris to eliminate insect eggs and disease pathogens and next season you'll have fewer pests in the garden.
You'll get larger onion bulbs that won't bolt in early spring if you sow seed or transplant seedlings now. Purchase the smaller onion sets for best performance. Bulblets should be only about half an inch wide. If they're larger, they may bolt in early spring. Plant larger ones to use as green onions through the winter, since they will bolt and set seed instead of bulbing in spring.
Practice Natural Pest Control
Make a routine of cultivating the top inch or so of soil in annual and vegetable gardens and around plants and trees. When you disturb the soil you'll bring overwintering insects and weed seeds to the surface. Birds foraging for food will get a snack, and you'll have less work next spring.
Bring Houseplants Indoors
It's time to bring houseplants in from their summer stay outdoors. Be sure to check them thoroughly for hitchhiking pests. This is also a good time to repot them in fresh potting mix. Toss the old mix out into the garden or onto the compost pile. Keep plants in a bright area indoors for a few weeks so they'll gradually get used to the darker, warmer, and drier indoor conditions.
Remove faded blooms of perennials such as coreopsis, Shasta daisies, delphiniums, penstemons, and yarrow. Divide clumps that are too large or ones that haven't bloomed much this year. After replanting, side-dress with compost, and water them well.