It was my love of homegrown salad greens that introduced me to the idea of fall and winter gardening. Like many northern gardeners, I had always assumed that the arrival of the fall frosts signaled a decisive end to the harvest season, but a little patch of arugula proved me wrong. One sunny October day, I walked up to our backyard vegetable garden to plant some garlic and discovered that my late summer arugula was still going strong. I immediately picked a big bowl and covered the bed with a row cover, a piece of fabric that I often used to protect spring-planted tomatoes. Yet, with that simple level of protection, we enjoyed arugula for an additional six weeks and I began to wonder what other vegetables could be grown so late in the year.
The ability to harvest throughout fall and winter has transformed our garden into a year-round food factory, but besides a non-stop supply of homegrown organic food, there are other hidden benefits. For example, because our cold-season leafy greens are tucked beneath the shelter of a cold frame or mini hoop tunnel, winter is the only time of the year that I don’t fight our out-of-control deer population — they’re left with nothing to nibble! As well, the winter garden is extremely low maintenance with little to do from November through March, besides harvesting. There’s no need to water or weed the winter crops and no slugs, cabbage worms, flea beetles or other common garden pests to foil my harvest.
I’m often asked, “How do you grow vegetables in late fall and winter — Isn’t it too cold?” Sure, it’s cold, sometimes very cold, but the defining factor of success isn’t cold, but rather day length and once the day length slips below the 10 hour mark (early November in my region) most plant growth comes to a standstill. Therefore I’m not really “growing” food after November, but rather just sheltering the cold-tolerant crops which patiently wait in their protective structures until I’m ready to harvest.
The planning of a fall and winter garden begins in early summer when leftover seed packets are sorted and last-minute orders to seed catalogs are placed. At this time, the seed of slower-growing leafy crops like kale, collards and cabbage can be started indoors under grow lights for a mid-summer transplanting to the garden. Quick-growing salad greens are direct seeded from mid-August through mid-September, but if daytime temperatures are still soaring in late summer, I start several flats of lettuce, endive, escarole, Swiss chard, pak choi and mizuna under our grow lights indoors. Many of these cool-weather crops won’t germinate outside if temperatures are too hot, so starting seeds indoors for later transplanting to the garden ensures a good harvest.
Season Extending Techniques
The key to a successful cold-season harvest is to select the right crops and pair them with the appropriate season extender. In our 2,000-square-foot garden, I rely on row covers, cold frames and mini hoop tunnels.
• Row Covers. It may look like a flimsy piece of fabric, but a row cover can easily extend the autumn harvest by about a month. There are several grades of row covers — light, medium and heavyweight — with each offering varying degrees of frost protection. The covers can be laid directly on top of salad crops in spring and early fall, but with the heavy frosts of late autumn and during winter, they will need to be “floated” over top on hoops or other supports to avoid damaging foliage.
• Cold Frames. If I could only have one season extender, I would choose a cold frame, a bottomless box with a translucent top that allows light to enter. A cold frame is an easy way to enjoy a bumper crop of gourmet salad greens throughout autumn and winter. The most basic type of cold frame is made of straw bales arranged in a rectangle and covered with an old window pane, shower door or a piece of clear polycarbonate material. Our 3 by 6-foot cold frames are built from 2-inch local hemlock and topped with Lexan, a twinwall polycarbonate that is more insulating than a single glass panel, less breakable and also offers high light transmission.
• Mini Hoop Tunnels. A mini hoop tunnel is an easy-to-build structure that can be erected quickly over garden beds to offer autumn protection to salad crops and herbs, shelter tall, leafy kales and collards over winter, or overwinter immature greens like spinach for an extra early spring harvest. In late summer, I also use a mini hoop tunnel, covered loosely with shade cloth to establish beds of salad greens for autumn and winter. The shade cloth cools the bed and boosts seed germination.
To make the hoops, I use 10-foot lengths of ½-inch wide PVC electrical conduit, bending them into an upside- down U on the top of the garden beds. To secure the hoops, we pound 1-foot long rebar stakes every 3-feet or so along the bed, with the ½-inch PVC slipping easily over the rebar. For spring and fall protection, I often use a row cover, but for winter, I add a layer of 6 mm greenhouse poly over the top of the fabric for added insulation. Secure your covers well with sandbags, rocks, logs or clips.
• Mache. Also known as corn salad, mache is an extremely cold-tolerant salad green that forms tidy rosettes in our autumn garden and winter cold frames. We harvest the small plants whole by slicing them off at soil level with a sharp knife, tossing them with olive oil, fresh lemon juice and a dash of salt for a simple, but sensational salad. The plants grow just 4 to 6 inches in diameter and should be direct seeded six to eight weeks before the first fall frost. Come spring, leftover plants quickly self-seed, so if you don’t want a carpet of mache babies, pull the plants before they set seed.
• Claytonia. Also called ‘Miner’s Lettuce’, Claytonia is native to North America and a workhorse in our winter cold frames. We direct sow the tiny seeds about six weeks before the first fall frost, but it’s not until the cold temperatures arrive in November that the plants really begin to grow. The tender leaves can be picked throughout winter, with the plants eventually producing delicate, edible flowers.
• Mizuna. Packing less heat than peppery mustard greens, mizuna is a welcome addition to the autumn and winter salad bowl. The mild, cabbage-like flavor pairs well with other greens for mixed salads, or toss the mature leaves into stir-fries or wraps. Direct seed mizuna in cold frames or the garden two months before the first fall frost. In our garden, the deep green, brushed with purple foliage of purple mizuna has made it a favorite.
• Pak Choi (Bok choy). Thriving in the spring and autumn garden, pak choi produces rounded, spoon-shaped leaves in green, red or purple. I like to pick the plants young, when they’re just 3 or 4 inches tall, tossing them whole in stir-fries or adding the leaves to salads. Direct sow eight weeks before the first fall frost in cold frames or garden beds. Try ‘Ching Chang’ or ‘Extra Dwarf.’
• Spinach. Spinach is a great choice for a fall and winter vegetable garden. Not only does it prefer the cool, short days of autumn over the heat of summer, but it also appreciates the ample moisture that fall often brings. Direct seed in a sunny area of the garden in late summer when the night temperatures begin to drop and within weeks, you will be rewarded with a dense patch of deep green leaves that will continue to produce until the hard frosts arrive. If you cover your bed of spinach with a row cover or mini hoop tunnel, the harvest can easily be extended into winter. Try ‘Monstrueux De Viroflay’ or ‘Giant of Winter.’
• Arugula. It was a simple patch of arugula that introduced me to cold-tolerant crops and brought winter gardening into my life. Today, we grow arugula year round, even in summer, when I sow seed in the shade cast by my tall A-frame trellises. For a fall and winter crop, plant arugula seed four to six weeks before the first frost, sowing in both garden beds and cold frames.
• Swiss Chard. Unlike arugula or pak choi, which can bolt quickly at the arrival of summer, Swiss chard is a non-stop food machine, lasting well into late autumn even without the protection of a season extender. Pair it with a cold frame or mini hoop tunnel, and you’ll enjoy the nutrient-rich leaves into mid-winter. Opt for varieties like ‘Rainbow,’ ‘Flamingo’ or ‘Orange Chiffon’ that have brightly colored leaf stalks.
• Tatsoi. With tatsoi in my cold frames, I say to Old Man Winter, “Bring it on!” Tatsoi shrugs off the coldest weather, forming low growing, deep-green rosettes in our cold frames. Pick the leaves individually for cold-season salads, or pull the young plants whole for a stir-fry. We also grow tatsoi as a fall crop in the open garden, sowing the seed about six weeks before the first fall frost.
• Lettuce. Like spinach, lettuce thrives in the cool temperatures and increased moisture of fall. Start sowing seed directly in the garden about eight weeks before your first fall frost. Because lettuce seed won’t germinate well once temperatures are above 77 degrees Fahrenheit (25 degrees Celsius), you can also start your seeds indoors under grow lights and move them to the garden about six to eight weeks before the first frost. Top cold-season picks include ‘Winter Density,’ ‘Brune D’Hiver,’ ‘Outredgeous,’ ‘Red Salad Bowl,’ and ‘Rouge D’Hiver.’
• Kale. No autumn veggie patch is complete without several varieties of super-hardy kale. In fact, as temperatures drop in autumn, the leaves of kale become even sweeter! Transplant seedlings into the garden in early summer for a non-stop crop of kale or sow seed thickly in garden beds in August for a bumper crop of baby leaves to toss in salads and stir-fries. Favorites include ‘Lacinato’ (also called Dinosaur kale or Black Tuscan kale), which has excellent-tasting and highly puckered blue-green leaves, or ‘Red Russian,’ a cold-tolerant kale with gray-green leaves and vivid purple stems. Don't forget about the cool- and cold-tolerant salad herbs that can also be fall and winter harvested. I add clumps of chives, thyme, parsley and chervil to my cold frames in late summer, as well as a few cloves of garlic to supply aromatic foliage that can be clipped to add a flavorful kick to salad dressings.
Summer planting offers its share of challenges, as many fall crops are seeded or transplanted in mid to late summer when drought and heat rule the garden. To overcome this double whammy, seeds can be started indoors under grow lights, but there are a few other things you can do to ensure your fall garden has a chance to get established.
1. Provide moisture. Garden beds dry out much quicker in summer than in spring, so be sure to get out your hose and keep newly seeded or just transplanted seedlings well watered.
2. Provide shade. A simple shade cloth suspended on hoops above a garden bed will block a portion of the sunlight and help keep soil moist and germinating seeds and young seedlings cool.
3. Pick the best time. Planting when the forecast predicts hot, cloudless weather for several days is not the best time to put in your fall vegetables. If possible plant on
a cloudy day or just before a rain.
4. Mulch it. After transplanting seedlings of vegetables like kale, broccoli or kohlrabi, water well and spread a layer of shredded leaves or straw over the bed to lock in soil moisture and prevent wilting.
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