Prepare Your Garden Beds Now for Winter
“The seed is in the ground / Now we may rest in hope while / darkness does its work.”
—Wendell Berry, “1991, V” from A Timbered Choir
STORY BY BILL THORNESS
In late autumn, my gardening thoughts turn not to the seed, but to the ground.
The philosopher, poet, and — perhaps most importantly — farmer Wendell Berry often refers to the soil, from which all life springs and returns.
The quote above meditates on the beginning of the cycle, when seed is sowed and we wait for the magic of germination to take place. But the idea could just as easily inspire us to focus on building a more fertile soil, so that we may reap benefits when again we sow. It’s an especially good topic at this time of year, when darkness above ground is impending, and Pacific Northwest gardeners “rest in hope” for a couple of rainy months.
What we do about soil fertility now relates directly to the success of next year’s garden.
You might think that by November it’s too late to do anything productive in the edible garden, but that’s not quite true. Whether growing winter vegetables or simply pulling up the last of the fall crops and “putting the garden to bed,” gardeners can still take measures to protect and enhance the soil. Focus on three actions — get a soil test, plant a cover crop, and lay down a mulch — to ensure soil health.
What’s an indication of healthy soil? Most obviously, see how plants are growing. But just because one crop did well this year doesn’t ensure a bounteous harvest next season. Like your doctor does when you visit the clinic, you need to conduct some lab work on your soil. In other words, get a soil test.
In the Pacific Northwest, fall is a great time to test the soil. After our main cropping season, it’s good to know how much fertility remains. We don’t add fertilizer now, but by protecting the soil over the winter, most nutrients will still be there for next year, and further nutrients can be added before planting.
King County residents are lucky: We can get free soil testing through the King Conservation District (kingcd.org). To help enhance water quality, KCD offers residents five free soil tests per residence per lifetime, with the intent that if we know the fertility of our soil, we won’t dump extra (costly, polluting) fertilizer into it. That extra just gets washed out into groundwater and adversely affects water quality in our rivers, lakes, and Puget Sound. People living outside the county can get inexpensive soil tests; check with the Garden Hotline (gardenhotline.org) for lab resources.
Most soil tests list the levels of N–P–K (nitrogen-phosphorus-potassium), your soil’s macronutrients. The tests also tell the pH, which indicates whether to add lime before planting, if the soil is too acidic. The test results might also list micronutrient or mineral levels. If you tell the lab what you’re growing in the bed, the results might also give specific fertilization instructions.
In the fall, nitrogen should be fairly low. This macronutrient is the leaf-growth food. It moves through the soil fairly quickly, and your summer crops should have gobbled up most of it. Don’t worry. It is the easiest macronutrient to add in the spring, and we can grow our own nitrogen by tackling the next step.
Plant a cover crop
Cover crops are fertilizers in disguise. Instead of powder that comes in bags, they’re leafy plant food that literally turns into fertilizer. How? Let a crop grow until it’s flowering, then cut it down and dig it into the soil. As it decays, it releases the elements of fertilizer into the soil and feeds the soil with microorganisms that help bring existing fertilizer to your plants.
Legumes are a great example. Those members of the bean and pea family take in atmospheric nitrogen and attach it to their roots for later use. Small, white, nitrogen nodules are visible on the roots of mature legume plants as they’re getting ready to flower. This “fixing” of nitrogen is a perfect job for a cover crop. When the cover crop is incorporated into the soil, those nodules break down and, very soon, provide nitrogen for other plants.
More great news: It’s not too late to plant it this year! Although November is too late to start most crops, one legume will sprout in very cool soil: fava beans. (Unless you’re in a cold micro-climate, fava beans should still germinate.) Sprinkle the seed on the bed and cover it lightly with soil. Keep it well-watered until it sprouts. If you’re in a cool area, cover it with floating row cover or mulch to aid in germination.
Along with adding nutrients as they grow and delivering more nutrients when cut down and dug in, cover crops protect the soil from winter rains. Steady or heavy rain causes nutrients to leach out of the soil, just like excess fertilizer. Just like a tree keeps you dry when you stand under it in a rainstorm, cover crops keep the soil from getting pounded by the rain, thus slowing down the leaching process. Rain can also cause soil compaction, which can suffocate soil biota, and the cover-crop canopy shields the soil from that problem as well.
Go mad for mulch
If sowing a cover crop requires more effort than you can muster, at the very least protect the soil and its web of life by blanketing the garden with a winter mulch. Great gardeners rave about its benefits.
While not as frugal as growing your own fertilizer, mulching will pay dividends. Mulch shields the soil from compaction and excess leaching and protects it from desiccating winter wind. This also creates a more hospitable environment for the soil biota, which are necessary for a healthy soil that makes nutrients available to plant roots.
And mulching is pretty easy. Get a bale of straw (many garden centers now sell them, or visit the farm supply store out beyond the suburbs), break it up, and layer it on top of the soil to a depth of 2–3 inches. Compostable materials also work, such as fallen leaves or disease-free plant material that you’ve pulled out of the garden during fall cleanup. Don’t mulch your tomato plants that have been wilted by late blight, but do mulch the spent flower stalks of echinacea, for instance. If you live in a high-wind area, cover the mulch with a wire mesh to keep it from blowing away.
Mulch is also useful to stave off frost or desiccation of winter vegetables. Tuck a thinner layer of mulch around your brassicas and root crops, and cover the planted garlic bed with it, pulling it aside once you see the young shoots pop through in January.
If you spend a little time now to test the soil, plant a fava cover crop, or mulch the beds, the edible garden will be ready to bounce back to life and feed you hope anew when you put those first seeds in the ground next season. Inevitably, as winter follows the harvest, the calendar soon enough turns toward spring.
Bill Thorness is the Seattle author of Cool Season Gardener. He can be found this month bedding rows of garlic cloves under a golden straw quilt.