O Winter, ruler of the inverted year.
—WILLIAM COWPER
For the first six years of our commercial winter-harvest production we sold vegetables only from October 1 through May 31 (“the other eight months” as we referred to them). In addition to a baby-leaf salad mix our cold-house crops included carrots, spinach, mâche, leeks, and scallions, plus tatsoi, pak choi, and other Asian greens. From the cool houses we had radishes, turnips, turnip greens, Swiss chard, watercress, parsley, and arugula. From storage there were onions, garlic, shallots, winter squash, celery root, parsley root, scorzonera, and storage beets. In spring both the cold and cool houses provided early crops of arugula, carrots, baby beets, baby new potatoes, broccoli, fennel, kale, lettuce, turnips, and overwintered onions.
Those six years helped us focus on developing the new concepts of the winter harvest, and it was time well spent. We worked on refining many of the unique greenhouse-design and cropping programs that this book discusses. We were aware, however, that to achieve the economic potential of the small farm we would need to reincorporate summer production in the future. And so we did by adding tomatoes, peppers, eggplants, and cucumbers in the greenhouses, and artichokes, beans, cabbage, cauliflower, celery, melons, peas, radicchio, summer squash (in addition to many of the crops listed above) in our outdoor fields.
The next few years, during which we ran full production both summer and winter, were truly exhausting. It is difficult to work at the flat-out speed that small farming demands for twelve months a year with no break. Although the economic returns were in favor of summer crops (our gross for the four summer months was slightly above that for the eight winter months) we were very aware that the winter months contributed importantly to the summer by getting our crops ready earlier in spring thus allowing us to establish ourselves in new markets in addition to keeping hold of our regular markets after the summer season ended. At present we reconcile all of these factors by scheduling a four- to five-week vacation for our crew and ourselves at the time when plant growth, customer interest, weekly income, and our energy levels are at their lowest ebb—late December to late January.
Fall and Winter
We achieve this by timing our end-of-summer/early-fall sowing dates to maximize fall greenhouse production from November 1 right up through December 21. (We can successfully harvest many crops from outdoor fields until the end of October.) That allows us to sell everything we can possibly grow in the high-demand pre-Christmas market. In addition we have simplified our production during the winter months. At present, spinach, sown in mid-September, is the only multiple-harvest overwintered green crop we grow. We harvest the spinach so heavily to meet the December demand that it needs a month to recover before the first new-year harvest in late January. In order to save labor we don’t do mesclun in fall but grow head lettuce instead. As we harvest the once-and-done greenhouse crops in November and December (lettuce, radish, turnip, baby pak choi, celery, fennel, scallions), spaces open up and we re-prepare and resow them to crops that will start maturing from mid-February on. Thus by the end of December we have picked all the crops that were sown for fall harvest and have replanted the greenhouses to crops that will be ready for the late-winter/early-spring harvests to come. Our four- to five-week vacation commences at the winter solstice.
During the years when we experimented with adding minimal heat to our largest greenhouses (see chapter 7) we were able to keep producing a far wider variety of crops than just those available from cold houses during the first two months of the new solar year that begins after winter solstice (the most difficult period for a cold-house grower). We were proud of the variety and quality we could offer and pleased to be able to consistently supply our customers every month of the year. However, our records show that expenses were at their highest (due to fuel costs) and yields were at their lowest (due to slow growth) during those weeks.
Spinach in a cold house before being covered for winter.
There was also another disadvantage. In order to be able to harvest during those weeks we needed a good bit of greenhouse space dedicated to crops sown for January/February harvest, which meant that we had less to sell in November/December. By aiming greenhouse production as we do now to maximize the November/December sales and running all our greenhouses as cold houses, we sell just as much but cut way back on expenses and hassles. During the five weeks after winter solstice there are just our “candy carrots” and overwintered leeks to harvest and sell fresh (until we run out of them in mid-February) but we are able to hire someone to do that for us during our vacation.
The Dependable Spinach Crop
Overwintered spinach has become our major winter green crop for three reasons. First, it is the perfect winter green for the cold houses. Spinach continues producing new leaves all winter unlike, say, kale, another cold-hardy crop, which stops new growth during the cold months. Second, it is an enormously popular winter crop and the demand is always more than we can supply. And third, the timing is perfect for the crop rotation we use in that mobile greenhouse. Mid-September-sown outdoor spinach is hardy enough not to need protection until the season is over for the summer crops in the greenhouse. We then move the house over the spinach during the second half of October. We start harvesting around Thanksgiving (our spinach harvest comes from the field through the end of October and from another greenhouse during November), and each bed will provide four harvests at about monthly intervals before the spinach starts thinking about going to seed in late March. After the final harvest, we clean up and prepare the beds for an early-April transplanting of our earliest tomato crop. At that point what was a cold house all winter becomes a warm greenhouse because we turn on a propane heater that has sat dormant all winter so as to maintain a 60°F night temperature for the tomatoes.
Crop Rotation
We aim to harvest at least three crops per year from every square foot of the cold houses—two in winter and one (or more) in summer. A typical rotation in one of the 48-foot cold houses might include a winter-harvested carrot crop followed on March 15 by planting the first of the baby new potatoes. After harvesting the potatoes, we would transplant a summer crop of Charantais melons in late May. After we cleared the melons the house would be planted to a fall-harvested spinach crop. Then in late November we would move the house to cover a later-planted spinach crop for spring harvest.
Succession plantings for mid-winter harvest in our cool house.
In another 48-foot cold house we might have grown a rotation of fall stir-fry crops and early spring lettuce. Following those we would set out six-week-old tomato plants on May 10 and protect them with an inner layer. Once it was safe to remove the inner covers, the tomatoes would be trellised to the overhead supports to keep them productive as long into the fall as possible. A green manure of red clover might be undersown in the standing tomatoes on September 1 and the tomato vines would be unclipped from the overhead supports the day before the house was due to be moved to cover a winter crop of carrots in late October. This rotation would repeat a second year on the uncovered site before being exchanged with a different rotation in another house for the subsequent two years.
Spring in the cool house.
With the supplementary heat in a cool house we can plant and harvest four crops and sometimes even five during the winter months alone, and we always grow heat-loving crops in there over the summer. Since the cool-house crops are almost evenly divided between the lettuce family (Compositae) and the cabbage family (Brassicae) we make sure that they are alternated with each other in addition to alternating with the warm-weather crops (cucumbers, peppers, eggplants) in order to have as complex a rotation as possible.
Our original cool house is nonmobile. Therefore we are very particular about soil preparation, quality of compost, crop rotation, and irrigation in order not to create pest problems or accumulate excess salts. We have succeeded in keeping that house highly productive for fourteen years thus far. Growers need to be aware that soil problems in greenhouses years ago were what spurred interest in the first movable greenhouses. It was traditional to dig the soil out down to 16 inches deep and replace it with new field soil when problems arose. The pioneers of movable greenhouses realized that it would be far less work to move the greenhouse, and I will talk more about that in chapter 10.
There is no single perfect crop rotation or yearly schedule in this business. The differences in markets, climates, and growers’ preferences assure endless variations. And that is what makes exploring the winter harvest so stimulating to the agricultural imagination. I know many growers who have started with a greenhouse just to get a jump on spring, then used it to extend production into the fall. Next they explored planting even earlier spring crops, and eventually became four-season growers. They all talk about how involved they have become with the thinking and planning required for pursuing new crops and new cropping sequences. Farming in the summer months is fascinating, but farming for twelve months is even more so.
Tomatoes continue growing in the mobile greenhouse while winter crops have just been planted outside.