The Winter Harvest Handbook

Baby-leaf (mesclun) salads are an ideal crop for the winter harvest since immature leaves of the salad crops are far more cold tolerant than mature ones. Our mix has included red lettuces, green lettuces, broadleaf arugula, sylvetta arugula, endive, narrow-stem chard, claytonia, minutina, spinach, mâche, watercress, and beet leaves. All are carefully chosen, naturally hardy, winter-salad varieties. As we state in our advertising, based on nutritional data from the U.S. Department of Agriculture, this salad blend contains at least 5 times more calcium, 4 times more iron, 12 times more vitamin A, and 6 times more vitamin C than a salad of head lettuce.

Quality should be the primary concern of any baby-leaf salad grower. We work hard to set rather than just follow the quality standards. We don’t sell salad mix ingredients that are too large, or bitter, or tough, or stringy, or frost damaged. If we are not completely satisfied, we leave that ingredient out of the mix until conditions improve. These evaluations have led us to move some crops for midwinter harvest in the cold houses, such as claytonia, from the colder edge beds to warmer inner beds; to do more succession plantings of some crops like minutina and narrow-stem chard so as to have more new young leaves coming along rather than relying on regrowth; to cut back some other crops earlier—red-oak lettuce, for example—because the regrowth is hardier than the initial leaves; and to continually do trial plantings of both standard and potential crops so we can identify cultivars better suited to our conditions, in addition to finding new flavors, shapes, and textures for the mix.

Our mix is composed only of whole baby leaves that are washed, mixed, and packed directly after harvesting (as described in chapter 15). Ideally, leaves are no more than three inches in length. We believe a quality mesclun must have leaves that easily fit onto a fork and into the mouth. We have seen salads sold locally containing mizuna leaves with seven- to eight-inch-long stems. In our opinion, overgrown leaves are better consigned to a braising mix or sold bunched as cooking greens.

Maintaining our quality and size standards is not easy, because we also do not chop mature plants into small pieces like the cut-up endive and radicchio seen in supermarket mixes. Instead, we grow an Italian endive cultivar, ‘Indivia Bianca Riccia da Taglio’ (white curly endive for cutting), sold by Johnny’s Seeds as ‘Bianca Riccia’, which has nice light-colored frilly leaves at the baby-leaf stage.

We have sold quite a lot of ‘Bianca Riccia’ to restaurants both in winter and summer as an individual crop. We thought that the pretty yellow color, the unique shape, and the crisp texture would make the leaves very appealing on the plate as a bed under a meat or seafood entrée. Restaurants like to use the names of novel ingredients on their menus, but we knew ‘Indivia Bianca Riccia da Taglio’ was a little too much of a mouthful. So in order to get the restaurants interested we decided to rename it. (See also Swiss chard,) Since it is an endive with a lovely golden color we christened it “golden frisée” and sales took off.

We haven’t yet found a radicchio that we like for baby leaves, but we actually prefer ‘Bull’s Blood’ beet leaves for red color, and so that’s what we grow. The cool conditions of our winter greenhouses intensify the beautiful deep maroon, and the flavor does not have radicchio’s bitter edge (which under poor growing conditions can become so bitter as to ruin the whole salad). Cool winter temperatures keep arugula and watercress from becoming too strong and biting. In fact, we purposely do not add the usual hardy oriental greens to our salad mix because our customers prefer a salad without the mustard tang. Many parents have told us this is the only mixed salad their children will eat because they prefer the milder, cool-weather flavors of our ingredients. We sell the hardy oriental greens along with spinach and ‘Bull’s Blood’ as a separate braising mix.

There are three components of our winter mix—lettuce, endive, and arugula—that do not consistently meet our quality standards once temperatures get too cold for too long. We have traditionally given them a little protection in our cool house during January and February. Although we have found some lettuce varieties, principally the oak-leaf types, that are very cold hardy at the baby-leaf stage, their quality during parts of January and February is better from the cool house than from under the inner covers of the cold houses. The same is true for ‘Bianca Riccia’ endive and standard arugula. The wild arugula sold as ‘Sylvetta’ is perfectly hardy, but we need to learn more about its soil-fertility needs and timing of planting to make it as successful as we know it can be. At times, we have sold salad mixes without these three ingredients, and our markets have accepted them. However, we prefer to sell a consistent product. So we have continued to grow these three in a cool house while pursuing our search for hardier cultivars and for the best warmth-conserving inner- and outer-cover combination.

Despite our preference for producing a consistent salad mix with the same percentage of each leaf type every time, reality occasionally intrudes in winter. Extreme weather, poor germination, or poor quality of certain crops can cause us to modify the quantities of the different ingredients. The farthest overboard we have gone was one mix that was 50 percent claytonia, and another that was 50 percent baby spinach. A nearby upscale restaurant with its own winter greenhouses found itself with only claytonia available for a two-week period one January and used it with great imagination. It would appear that both our and their customers are adventurous enough to be forgiving of occasional slips. The key is to maintain a high quality standard even when your consistency slips off the rails for a brief period. See appendix E for a chart of sowing dates for a succession of fall and winter salad harvests.

Our braising mix is made up of a preponderance of hardy Asian greens. We cut the leaves slightly larger than our baby-leaf salad but never more than 4 inches long unless we are desperate. Our choice of varieties for the braising mix excludes any leaves that are not normally cooked. That rules out mâche, lettuce, claytonia, and endive by our standards. The mix includes spinach and chard in addition to all the Asian greens (mizuna, mibuna, tatsoi, pak choi, tokyo bekana, etc.). We tried the red-leaved mustards but none of them have sufficient color in winter, so we use the ‘Bull’s Blood’ beet leaves instead. Spinach is not necessary if the tatsoi supply is good, but we do like the chard leaves for their tenderness. Many customers have told us they like this mix for a raw salad as a change of pace, so we sell it as an Asian salad/braising mix.

The possibilities for experimenting with winter mixes are nearly endless. One thing to figure out is how much of each ingredient you need to plant to meet demand and how often to plant to get the harvest timing right. Another is gauging how the plants will react to cold conditions—whether their quality will remain high, and how soon they will bolt to seed.

We did a trial one year to see what crops could be planted later in the fall to supply a baby-leaf Asian salad or stir-fry mix in mid-February, the coldest time of our winter. We planted a broad selection of oriental greens on October 25 in one of our unheated houses. On the 15th of February we harvested a salad mix consisting of 4-inch-tall plants of the most successful cultivars. They included ‘Joi Choi’, ‘Yu Choi’ (edible rape), ‘Mei Qing Choi’ (baby pak choi), tatsoi, and mizuna. They all need to be harvested promptly at that stage because within a week afterwards all but the ‘Joi Choi’ started to go to seed. The ‘Joi Choi’ continued to grow, and we sold them bunched as “baby pak choi” until the end of March.

One winter we took advantage of the hardiness of Asian greens and their culinary possibilities by putting together a main-course item we called the “Stir-Fry Pak.” This was a 10-by-15-inch cellophane bag containing the following whole ingredients: a head of ‘Mei Qing Choi’ pak choi, a head of young tatsoi, one ‘Shunkyo’ semi-long pink radish, one ‘Hakurei’ turnip with greens, one ‘Tadorna’ extra-hardy leek, and a large carrot. The beauty of the contrasting colors and shapes of root, stem, and leaf plus the customers’ pleasure at finding all the ingredients in one bag made our “Stir-Fry Pak” a market success, so successful in fact that the trial plantings sold out by mid-December before the mature leafy greens got a true cold-weather testing. However, we know the tatsoi, leek, and carrot can withstand our coldest conditions and we continue to experiment and learn more about the others.

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Our “Stir-Fry Pak”—all the ingredients sold together in one easy-to-purchase bag.

The February 15 salad mix also included some very sweet inner leaves from a September 1 sowing of ‘Dwarf Scotch Curled Kale’, the best eating of the traditional kale varieties we have grown under the inner cover. Those plants produced beautiful kale for early-to-mid-March sales before starting to bolt the third week in March. For a spring, summer, and fall kale variety we grow a Tuscan kale exclusively. It goes by the names of ‘Toscano’, cavalo nero, dinosaur kale, ‘Nero di Tuscana’, or black kale. Both we and our customers think it is so delicious as to almost transform kale into another vegetable entirely.

“Sweet Winter Carrots” are our most acclaimed winter crop. Parents in nearby towns tell us all the time how much their children like these crunchy treats. We leave these carrots in place in the soil under the cold houses, digging them over time as needed. The most successful variety we have found thus far for wintering in the soil is ‘Napoli’, a small-size but full-flavor carrot. We plant for October harvest during the last week of July and for later harvests, the first week of August. We plant in soil fertilized by turning under a soil-improving green manure of oats and peas a month before we sow the carrots. We cover large areas of carrots with mobile greenhouses in late October. Our “Sweet Winter Carrots” are always dug fresh from the soil in which they grow; we dig them outdoors in October and November and from the greenhouse-covered beds in December, January, and February. The in-ground, cold-soil storage further enhances their flavor, sweetness, and raw-eating crunch so that the last ones harvested in late February are even sweeter than the first. Since the tops remain green under the inner layer, we sell our carrots with one and one-half inches of green top at all times. This makes for a beautiful pack and identifies our carrots as “freshly harvested” rather than from storage, allowing us to charge a premium price.

These carrots have an almost legendary popularity in our markets. We cannot grow enough of them to meet the demand. The tastiness resulting from fall growing and cool-soil storage elevates the humble carrot to another plane. While delivering in our stores we have seen little children rush to the produce counter, entreating their parents to buy lots of “candy carrots.” This crop is at its best for only a five-month season from October through February. Once new top growth begins in March, they start to lose their sweetness.

We have experimented with extending the harvest season of our sweet carrots, but we haven’t succeeded yet. We tried adding a layer of insulation over some beds in mid-January to forestall spring regrowth, but that prevented the important daily influx of sun warmth, causing the carrots and the soil to freeze solid for weeks. The carrots were of poor quality when they thawed. We have also planted carrot varieties that resume their root growth in spring from a late-September/early-October sowing date in hopes of finding one that would be harvestable in April. Thus far the flavor has been disappointing.

We sow a new crop of carrots during the winter to sell in the spring. Our new-year sowings of carrots, made in late December following fall lettuce, are ready for sale by May 10. For these we use the variety ‘Nelson’. This is a deliciously sweet spring carrot, but no matter how tender and flavorful our spring carrots may be, they cannot match the acclaim of our sweet winter carrots.

If we were to grow only one leafy winter crop, it would be spinach. We sell spinach both as small leaves in the salad mixes and as large leaves for bulk sales. In both cases we harvest only whole leaves without stems. This is slower work than harvesting entire plants, but we continue to do it because it is worth it: the regrowth is much better, which means greater total yield per square foot, and the quality of the product is exceptional enough to command a commensurate price. We harvest with a very sharp small-bladed (bird’s-beak) knife and find we have become very efficient with practice.

In our climate spinach planted outdoors during the second to third week of September in well-composted soil and then covered with a greenhouse by late October is ready to harvest for Thanksgiving sales. The plants continue to produce, yielding four more harvests per bed until late March/early April. We devote almost half of our total greenhouse space to winter spinach. For more on spinach, see The Dependable Spinach Crop and Managing Quick Hoops.

Leeks are almost a year-round crop for us and would be all-year if the winter leeks did not sell out so quickly. We get our first crop in May from transplanting extra early seedlings to a cold house. (Seeds are sown February 15 in our plant-starting greenhouse.) Then we sell outdoor-grown summer leeks through September and the fall leeks through November. Winter leeks are available from early December until we are sold out, usually in early March. We use a different leek variety for each season. The summer and fall leeks are harvested directly from the field with the additional protection of a sheet of plastic over the last of the fall leeks during the second half of November. We protect the winter leeks with a movable greenhouse starting in early December. We add an inner layer from mid-December on until all the leeks are sold.

The edible part of a leek is the white blanched stem. The more length a blanched leek stem has, the better the product. Blanching can be accomplished by hilling soil up against the stems of the leeks. However, in our experience, the key to growing leeks efficiently and intensively is to grow your own transplants and dibble them into deep planting holes. By dibbling in the transplants rather than having to hill-up soil as the leeks grow, we are able to plant them more intensively—as closely as three rows on a 30-inch bed with the leeks 4 inches apart in the row.

Unlike many of our other crops, we don’t grow our leek transplants in soil blocks. Instead, we grow them on the floor in our plant-starting greenhouse in 30-inch-wide-by-8-foot-long-by-3-inch-deep seedbeds with wooden sides filled with potting soil. We sow leek seeds directly into these beds using the six-row seeder (see chapter 13). We allow the seedlings to grow in these beds until they are at least 10 inches tall. We dig them out of the seedbed by loosening the potting soil under them with a trowel. To prepare the young plants for transplanting, we trim their roots to 1 inch long and trim the top part to 10 inches long.

Our dibble is a 36-inch-long, 1-inch-diameter dowel with the end tapered to a spatulate tip. We sometimes attach a shovel handle to the upper end of the dowel and add a 6-inch-diameter plate 9 inches above the tip. In use we push it into the soil to the full 9-inch depth and then twist the handle so the spatulate tip flattens out the bottom of a 9-inch-deep tubular hole. This is more successful if the soil is moist, as dry soil will tend to collapse back into the hole when the dibble is removed. Thus, we water the surface before transplanting when conditions are dry. We make a hole every four inches along the row and simply drop a leek transplant vertically into each hole.

Once the seedlings are in the holes, only an inch or so of green top sticks up above the soil. Then we irrigate the field and let the leeks grow. We don’t intentionally refill the holes, but soil slowly migrates in every time we irrigate or cultivate. The leek plants grow beautifully, each with a guaranteed nine inches of blanched shank. If you have never grown leeks this way before you may find it hard to believe that it will work—but it does.

Our restaurant customers love early baby leeks. These we grow in a cold greenhouse at five rows to a 30-inch bed, setting them 3 inches apart in the row. At that spacing they can be cultivated with the long-handled wire weeder. Once when we had no other space, we planted single rows of leeks between the edge bed and the wall of the greenhouse. The dibble-and-drop method is the only way we could have done that.

Mâche continues growing right through the winter, no matter how cold the weather. With mâche you harvest and sell the whole plants. We often included mâche in the salad mix during December, January, and February, its best season. As an ingredient in salad mix, we prefer to cut it at three-quarters of full size.

Since mâche is not a cut-and-come-again crop, properly timed succession sowings are crucial for a steady supply. The late sowings—which allow us to have mâche available all through March—require even more precise timing (i.e., sowing October 25 for harvest on March 1).

If we have an oversupply, we sell full-sized mâche plants in bulk. In Europe mâche was traditionally sold in shallow boxes, one layer deep, with field-grit still clinging. We thoroughly wash our bulk mâche and sell it loose in our standard 3½-pound box.

Demand for our radishes is strong at Thanksgiving and for winter and spring holiday dinners. We succession-plant radishes in the cold houses and have sold them into December from a planting as late as September 30. Radishes are exceptionally mild and crisp in the cold houses in fall and spring but will not grow in winter once continuous freezing temperatures occur. We hope to find a radish cultivar for fall planting that would hold in the soil in excellent condition even after temperatures are too cold for growth.

Radishes can be grown all winter in the cool greenhouse. Radishes are useful as a quick crop in the spring season, and our market demand is stronger in spring than in fall.

We have purchased onion plants from the Texas growers and set them out in our cool houses the first week in January. We purchased the same short-day varieties that are traditionally grown in Vidalia, Georgia, and our harvest in early May was about the same time as theirs. These varieties produce very large, sweet, round bulbs that were a great hit with local restaurants looking for an early season specialty crop to mention on their menus.

We have also grown winter scallions because they are extremely cold hardy and can even be harvested frozen and recover nicely when they thaw. Unfortunately, Southern growers dump field-grown winter scallions in our markets at prices so low that we often don’t bother growing this crop. However, we highly recommend growing overwintered onions such as ‘Walla Walla Sweet’ and ‘Olympic’. We plant seed outdoors in late August and cover with a mobile greenhouse by late November. We sow at five rows per bed. We sell the plants from the two intermediate rows as scallions as soon as they are large enough in spring. We let the other three rows mature into bulbs that are ready for sale five weeks ahead of spring-planted onions. The return on this crop was not always commensurate with the length of time they took up greenhouse space, so we now winter them over under much simpler structures (see chapter 11).

Watercress can be grown like any other salad crop during the winter in the cool and moist conditions of a minimally heated greenhouse. We use boards to frame out 3-inch-tall-by-30-inch-wide beds on the concrete floor of our original cool house. We fill those frames with potting soil and sow twelve rows of watercress from seed. We place small misters (1 gallon per hour output) every 3 feet along the bed and run them continuously. Including watercress in our salad mix gave it an extra level of pizzazz, but we decided it was not cost effective. We get much better return selling watercress as an individual crop.

We’ve been successful growing exceptional quality beets and greens in a cold house both late into the fall and very early in spring (we’ve gotten beets to market six to eight weeks ahead of our outdoor spring crop). For the fall crop, since outdoor field beets can be sold quite late, we have found that a gourmet item like golden beets gives the best return. We choose baby beet varieties for the spring crop because they offer such a refined product when greenhouse grown. We sow them in our plant-starting house three weeks ahead of when we plan to put them in the soil. We sow them as multi-plant blocks (see The New Organic Grower, p. 149) at three seeds per block and transplant them out three rows to the bed at 10-inch-by-10-inch spacing.

Swiss chard has long been a popular winter greenhouse crop in France, but we have not found it an easy crop to sell in our markets. We decided that the large chewy leaves and long thick stems may look pretty but were not the most pleasant eating. In an effort to improve that situation we began doing succession plantings of Fordhook chard from which we harvested young, tender leaves, no bigger than your hand and without a stem, as soon as they reached that size. We could take four consecutive cuts before the leaf texture began to toughen. Since the young leaves are so tender and had no tough stem attached we decided a new name would help sales and started selling it as “butter chard.” Within two weeks after we introduced this “new” crop early one spring, half of the restaurants to which we were selling had added a “butter chard” salad to their menus. Such is the power of a little imagination in marketing.

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Left-hand leaf is the largest we allow in a baby-leaf salad mix. Right-hand leaf is the largest “butter chard” size.

We devote a considerable area to baby new potatoes in the cold houses each spring. We begin by pre-sprouting the seed potatoes for a month. We start in mid-February by holding the seed potatoes at 70°F for a week in our seed-starting greenhouse to break apical dominance and increase the number of sprouts. We start planting the middle of March. If temperatures threaten to freeze under the inner cover after the potato foliage has emerged we add an extra insulating layer of fabric at night. The first harvest of tender new potatoes is available by about May 10. ‘Rose Gold’ has proven to be the best variety for this early greenhouse production under our conditions. It is just as early as supposedly earlier varieties we have trialed and much more productive. We plant densely at two rows to the 30-inch bed (8 to 12 inches apart in the row), and we harvest at golf-ball size.

Our marketing success with turnips and turnip greens has been a pleasant surprise. The variety ‘Hakurei’ grows such sweet roots and tasty greens under cool conditions and in our well-composted soil that we can never grow enough to meet the demand. We harvest out of doors until late November from beds protected by quick hoops (see chapter 11) and from a cold house up until Christmas. We sow turnips at six rows to the 30-inch bed and thin seedlings to 2 to 3 inches in the row. We cut the greens off and sell them separately from the roots as this keeps both in better condition. You can keep producing turnips all winter in a cool house, but plantings sown from mid-November to mid-December will often go to seed right after the roots reach golf-ball size. You must pay close attention as the plants approach harvest readiness.

Over the years we have branched out past salad into more main-course offerings. Instead of overproducing just one crop like mesclun, for example, and then shipping it to distant markets, we prefer to sell a wider variety of fresh produce to our local markets (ideally no more than a twenty-five-mile radius from the farm). There have been days in the middle of winter when the produce counters of those local stores offered eight different cold-house crops from our farm side by side. We would like to make that twelve or more, and that’s why we keep experimenting.

Thanks to the greenhouses we get many of our spring crops to market three months ahead of the best we could hope to do with outdoor plantings. Our continuing research involves determining precise planting dates and greenhouse space allocation for each crop so as to have as wide a variety of vegetables available continuously from the greenhouses until they begin maturing outdoors. With all of our crops, those we grow now and those we may add in the future, we need to learn what strains are hardier, what strains are less susceptible to bolting, and what strains will germinate in cold soil. We are sure the biology of the vegetable world offers as many solutions as does the technology of floating covers and plastic greenhouses. The most important lesson from all of this is that there are so many possibilities yet to come. We are barely scratching the surface of what the winter harvest is capable of supplying.

It is exciting to think about a future in which the colder states are the source of a large percentage of their own winter vegetables. The northern part of the U.S. may not be able to supply all of its fresh winter-vegetable needs from simple protected microclimates, but we sure intend to push the envelope here in Maine. A winter harvest of a wide variety of crops is a logical step for farms that market their produce to subscribers or CSA members. Instead of trying to increase the number of members you serve each year, you could increase the number of months during which you supply food to your current customers.