September is the turn of the year from expansive heat and sun to the oncoming cool rains and cloudy days. I often think of the oncoming fall season as the slow start of a gradual siege that begins in the cool nights of August, with ever-increasing signs of an encroaching army: expanding spider webs covered with dew in the morning, dots of white fungus on the winter squash leaves, hungry rodents finding the low-hanging tomatoes in the hoop house. It is time to reinforce the walls of the garden fortress, plant the last crops for quick harvest, and make sure the root cellars are stocked with adequate provisions for the dark days ahead.
Luckily, the Pacific Maritime climate does not have devastating, deep frosts that level everything growing in a garden. Here, the hardiest crops can easily survive our mild winters. Semi-hardy greens can be protected against the few weeks of below freezing temperatures with temporary walls of floating row covers or by nursery quality plastic hoop houses. Root crops, vulnerable to voles and mice, can be lifted and stored in buckets of sand, where they continue to slowly grow in their new indoor soil. Like a classic medieval fortress, with concentric rings of thick battlements, cool food storage rooms deep within thick walls, and cloistered courtyards to maintain a few animals and small plots, the year-round garden can fend off the gathering siege of winter.
Beyond the surrounding moat, as it were, the hardiest crops stand up to the cold by themselves: the ordered ranks of leeks; the mini-towers of Brussels sprouts; and the green leaves of kale and collards, like waving plumes atop the helmets of mounted knights. They all will hold out quite well against low temperatures and high winds, suffering a few losses of outer leaves but maintaining healthy cores. Just behind the tall outer guardians stand the brave pages: the low-lying Miner’s lettuce and Mache (corn salad), evergreen all winter with tasty small leaves, as well as the Winter Bloomsdale spinach that will stand up to snow.
Less hardy greens and roots are the first inner circle of plants that need a bit of protection, including: broccoli raab, red and green mustards, hardy bok choy, winter lettuces and endives, and delicacies such as garden cress and gourmet dandelion. A waist-high hoop house of floating row cover, secured by movable carpenter’s spring-clamps for ease of access, will keep the more tender greens protected against the cold, while still watered by the rain, and growing minimally in the weak winter sun.
Fertilize a Bit
When preparing the soil for fall and winter greens it is important not to over-fertilize as too much nitrogen will lead to soft, leafy growth that will not stand up to cold. Better to add a minimum of nutrients for a good start, to allow the plants to grow sturdy stems and to gradually adapt to the increasing drop in temperature and sunlight. One nutrient that is significant to include, however, is a bit of kelp meal, which seems to help the plants ward off the cell-damaging effects of freezing. Hardy plants also adapt to frost by adding sugars to their internal chemical make-up as a botanical form of anti-freeze. That is why Brussels sprouts and kales taste so much sweeter after a touch of frost. Wait for the sugar.
There is also an alternative, manure-based method of warming up a wintertime raised bed. Pull the top 8-12 inches of soil aside and add a 6-inch thick layer of horse or other manure at the bottom of the trench. Replace the topsoil, making the sure the manure layer is well buried so it does not make contact with the plant roots above and supply too much nitrogen. Depending on whether it is fresh or well-aged, the manure will serve to a greater or lesser degree as a natural heating pad as it slowly decomposes all winter. Think of the now plumped up garden bed, with its subterranean source of heat, as resembling those old four-posters with thick mattresses piled up for warmth in the cold castles, with warming pans full of live coals swished between the sheets. Add a canopy of floating row cover above the bed and the winter plantings will be quite cozy.
Add Cover Crop
The remaining fall duty is to plant a cover crop in fallow areas. I prefer annual winter rye since it is economical and will sprout even if planted later than September. I protect the newly seeded area from birds with a swath of light row cover weighted down with a few stakes laid on top. Once the rye is 1-2 inches high, remove the fabric as the rye is now safe from the avian feeders stoking up for migration or local winter residency. A healthy cover crop prevents soil erosion during the winter rains and, when tilled into the soil in the spring before planting, adds tilth. The one caveat is that the resident rodents, particularly voles, will graze on the rye shoots all winter. At least they will not be munching on your root crops, which are much safer layered in sand in whatever large mouse-proof containers you can find. Old metal water-bath canners with lids work quite well, kept in a cool garage. Twist off the leafy tops, and make sure there are no cuts or rotten spots on the roots, which will remain firm for most of the winter.
Finally, to conclude the garden as a fortress in winter metaphor, I recall visiting the restored chateau in the Loire Valley where Leonardo da Vinci spent the last five years of his life as a guest artist, resident inventor, and intellectual companion to the king of France, Francois I. Leonardo followed a vegetarian diet, which was unusual for his time. The bedroom chamber where he died has casement windows that look out on an inner courtyard now lined with vegetable beds. In early January the garden was filled with lush artichokes and strutting peacocks.
Peter Heffelfinger, a Washington State University master gardener, has gardened organically on Fidalgo Island and the Skagit Flats for over 40 years. He has given workshops in year-round gardening for Transition Fidalgo/Eat Your Yard, Christianson’s Nursery, and at the Washington State University County Extension Service. He is a Salish Sea Steward, working on the invasive green crab survey.