Spend a few hours now to ensure your garden will be ready to burst into life next spring. If you're planning on planting bare root trees in January, dig holes now. Many fruit trees and plants like peonies, gardenia, lilacs, and bulbs need sufficient chill to thrive in the area, which varies from 700 hours to more than 1,600 hours. Find out your predicted first frost date and know approximately how many “chill hours” you receive.

Divide perennial plants that have tuberous, clumping root systems. Hints that you may need to divide your plants are clumps that didn't bloom vigorously, and clumps that didn't bloom in the middle. Remove the older parts and replant the younger, healthier ones. Cut back dry stems of perennials almost to the ground to tidy the garden and remove pest eggs and disease spores. Weeds are also on the removal list, but don't compost invasive weed seed heads. Dispose of them in a covered garbage container.

Pull any annuals that are fading and add to the compost. Save seed from annuals that will germinate true to type. A fair warning is not to compost morning glories, since they seem to have nearly a 100% germination rate. Discard in the trash any that have fungal disease. Take cuttings of geraniums, coleus, impatiens, and begonias to root for houseplants. Plant some winter blooms such as pansies, calendulas, stock, and snapdragons. Now is also the time to plant bulbs for spring bloom. Make notes or save labels of favorite annuals to remember them for next spring.

Consider planting a cover crop. It will increase soil organic matter, water permeability, soil pore spaces, nutrient-holding capacity, and improve soil structure. In addition, cover crops have other benefits such as weed control, reducing soil-borne diseases and nematodes (parasitic worms), erosion control, dust control, attraction of beneficial insects and spiders, attraction of beneficial nematode worms, as well as trapping nitrate residues left over from fertilizing the previous crop. Try legumes like clovers, field peas, or fava beans. 

Begin mulching after you've finished your garden cleanup.  Be sure your garden is well-watered before you begin. Pay special attention to evergreen plants. They will fare much better in the cold weather if they have received a deep watering. Lightly cultivate the soil and spread mulch evenly under plants. Mulch layers should not be heavy so the soil gets good air circulation, moisture, and the sun's warmth. Mulch will improve the look and the health of your plants. It will also improve the texture and structure of your garden.

It's also time to clean your gutters and put away your lawn furniture. Repair trellises and any other garden structures that need it. Move frost tender succulents to a protected area and be prepared to cover them if necessary. Clean and sharpen your garden tools and store them in a dry place. Clean pots and sanitize with a 10% bleach solution.

Climate zones in the Napa Valley, UC Master Gardeners of Napa County

Winterize Your Garden, UC Master Gardeners of Napa County workshop

Healthy Garden Tips, Cool Season Gardens for Napa County

http://acmg.ucanr.edu/files/121648.pdf

San Luis Obispo Master Gardeners