Fall is a great time to build healthy soil that will provide better crop yields, improve soil texture to absorb and hold water during the growing season, and discourage weeds, plant diseases and pests.
You want to avoid bare soil that will be compacted by the winter rains and lose soil nutrients with runoff. Covering the soil with burlap is not soil building.
Before you start, do some serious weeding in the fall. In the spring, follow up with weeding before you plant. Weeds come out much more easily after the soils are softened with the winter rains.
1. Plant a Cover Crop
Legumes (which fix nitrogen): Red clover, Fava beans, Austrian Field Peas, Vetch
Non-legumes: Arugula, Cilantro, Mustards, Corn salad, Calendula
Benefits: Plants cover the soil; their roots absorb rain; and cover crops create biomass, suppress winter and spring weeds, and support pollinators in early spring.
Spring: Cut plants to the ground and compost the tops. Dig in the roots 2 weeks before planting a new crop.
Bonus: Some cover crops are edible.
Critical: Plant early enough so there is good germination before cold weather begins.
2. Use Sheet Compost Mulch
Interbay Mulch (named after the Interbay P-Patch soil-building paradigm): Cover the plot with an equal mixture of BROWNS (leaves or straw) and GREENS (chopped garden waste that does not contain weeds that have gone to seed, coffee grounds, grass clippings, or brewery mash.) Mix the components and pile on top of the plot to a depth of 6 to 12 inches. Cover the pile with burlap bags or cotton sheets to hold the ingredients in place. Let the worms do their job. Mulch eventually breaks down and improves the soil.
In the spring, make indentations in the mulch and plant vegetable starts.
Lasagna Mulch: The ingredients are the same as above, but the BROWNS and GREENS are layered in alternating layers. No mixing is necessary. Cover with burlap or sheets or aged compost. Plant crops in the spring.
3. Plant Overwintering Crops
Plant crops that can be harvested in the fall, and/or will overwinter and yield crops in the spring.
August and September are optimum times to plant. See SeattleTilth’s Maritime Northwest Garden Guide for suggested crops to plant.
4. Bury Garden Waste
Dig a trench in your plot and bury weed-free garden waste. Cover with soil and plant.
Two links for a new method of building soil/raised beds that uses less water:
Fall is a good time to do a soil test, which will tell you the pH and list the nutrients that might be deficient in your soil. The King Conservation District offers FREE soil testing. Here is the link on how to do it:
Gardening Books for Seattle Gardening
Seattle Tilth’s Maritime Garden Guide
A favorite go-to book because it has monthly recommendations on what to do in the garden, along with tons of information on soils, fertilizers, plants, pests, etc. $16.95 at garden stores and nurseries
Vegetable Gardening in the Pacific Northwest
Lorene Edwards Forkner also includes a monthly gardening calendar format.
Winter Gardening in the Maritime Northwest/ Cool-season Crops for the Year-Round Gardener - 5th Edition, $17.95
Binda Colebrook explains all that you need to do to garden 12 months of the year.
Cool Season Gardener: Extend the Harvest, Plan Ahead and Grow Vegetables Year-Round , $18.95
Bill Thorness lives and gardens in Ballard, has taught winter-gardening workshops and has a blog.
Growing Vegetables West of the Cascades/ The Complete Guide to Organic Gardening - 35th anniversary Edition, $24.95
Steve Solomon, founder of Territorial Seeds, provides detailed information on growing specific crops, building soil, etc.
Growing a Revolution: Bringing Our Soil Back to Life
David Montgomery, UW professor of geology and MacArthur Award winner, writes about the microbes that give life to our soils.