The Winter Harvest Handbook

Work the lazy garden. You pay rent for it all winter, do you not? Make it earn dividends every month of the year.

If farmed intensively, a small area of land can be very productive. The key to increased productivity is to make better year-round use of every square foot. The most impressive skill of the old Parisian growers was their ability to develop techniques for maximizing output from their one- to two-acre holdings. When looking to expand production on our own farm, given our limited land base, we refer to finding the “hidden farm.” Whenever a section of our land is empty of crops and something could have been growing there, that is the hidden farm.

In our quest to find the hidden farm, the intensity of our cropping has reached the point where we grow almost no green manures anymore because we are growing commercial crops so early and so late. Yes, we lose the organic matter contribution from a green manure, but we gain the organic matter contribution from the root residues, outer leaves, and stems of the harvested crop in addition to the financial return from selling it.

We double-crop and triple-crop most of our outdoor fields. We also sow at much closer in-row and between-row spacing than used by large-scale field growers. Not only do we sow twelve rows of baby leaf salads or radishes or carrots on a 30-inch (75 cm) bed in the greenhouses, we use that same close spacing in the field.

Let’s take an area on which we plan to grow carrots as an example. We begin outdoor sowings as early in April as we can. Since we try to have every crop available all the time from the moment we first sell it, there are always fields set aside for later sowings of carrots. Some are areas we won’t need to sow until June or July. Rather than having those fields in a green manure or cover crop until needed, we use them for early production of unrelated crops, such as lettuce or spinach or Asian greens that can be harvested before the upcoming carrot-sowing date. The same holds true for fields where, say, lettuce will be planted later which are similarly used for an earlier unrelated crop.

Through focusing our planning on double- and triple-cropping, we have achieved gross yields per acre that are almost double what might be expected off our small acreage. Because we sell only in local markets (stores, restaurants, our own farm stand), we need to maintain a consistent production level of everything we grow, which requires even more planning and analysis. If we had a market where we could occasionally come in with large quantities of this or that crop and be able to sell it, we could keep every square foot planted continuously with much less forethought.

We keep harvesting hardy crops from our fields as late in the fall as possible in order to reserve the greenhouse space for even later crops. But we were always wondering if we couldn’t do more. In the spirit of Henry Dreer’s quotation at the head of this chapter, why should all those fields not covered by cold houses lie unused during the winter months? Given our climate, the only answer to that seemingly ridiculous question would be to build more greenhouses or sow lots of winter green manures. But the expense of a greenhouse is excessive if all we want to do is winter-over hardy crops for early spring harvest. And there are no winter green manures that can be sown and get established in this climate after our late-fall vegetable harvests.

From these musings, we evolved the idea of redesigning low tunnels for winter use. Obviously, crops that are actually harvested during the winter, like leeks, require the easy access of a walk-in tunnel, but we figured that low-growing overwintered crops for extra-early spring harvest would become an economically viable option if protected by a low temporary structure. For inexpensive overwinter protection of fall-planted crops such as onions, spinach, and lettuce, we now use low structures that we call “quick hoops,” and we have found them perfect for taking advantage of still more of our “hidden farm.”

The supports for our quick hoops are 10-foot lengths of ½-inch electrical conduit, either plastic or metal. Bowed into a half circle, they cover two 30-inch beds side by side with a path between them. We insert each end of the conduit about 10 inches into the soil on either side of the two beds, forming a hoop about 30 inches high at the midpoint. Plastic conduit can be bent as you put each support in place; metal conduit must be pre-bent to the ideal shape with a tubing bender. We place one hoop every 5 feet along the length of the beds (which are usually 50 or 100 feet long). The hoops are then covered initially with 10-foot-wide spun-bonded row cover held down by sandbags placed every 5 feet along the edge (we use the same kind of sandbags as those that hold down the plastic bottom edges of the rolling houses).

Setting the ½-inch plastic electrical conduit for a row of quick hoops.

Onions, scallions, spinach, and lettuce are the first crops we tried overwintering under quick hoops, and we continue to grow these. We plant overwintering onions during the last week of August and place the hoops and the row cover over them in mid-October. As described in chapter 8, we plant onions five rows to a bed so that we can harvest the two intermediate rows as scallions. We start harvesting the scallions as soon as we begin to remove the quick hoops in the spring, which leaves space for the remaining three rows to develop bulbs. The advantage of overwintered onion varieties is that bulbs mature at the end of June. That gives us onions to sell at our stand for five weeks or more before the spring-planted crop is ready.

Three rows of quick hoops cover the same area as a 22-by-48-foot greenhouse at 1/20 the cost.

For spinach and lettuce we either sow directly in the soil or seed in soil blocks. Transplants may be better in some cases because outdoor germination of direct-seeded crops at this time of the fall can be spotty. We seed soil blocks on October 1 and transplant them out two weeks later.

Direct-sown seeds would go in at a slightly earlier date. Later sowings will mature later in the spring than earlier sowings, but sowing too late can result in crop failure if the seedlings fail to establish well enough to survive the winter. After setting out the plants we cover them with row cover in mid-October, the same as with the onions. Overwintered lettuce and spinach will give you outdoor crops to sell up to a month earlier than the best you can do with spring transplants. It is important to choose varieties that are hardy enough to put up with the stress of overwintering.

Once real winter weather threatens (late November/early December) we add a sheet of 10-foot-wide clear plastic over the row cover to make the quick-hoop tunnels more snow proof. To stiffen the structure against wind and snow load, it’s important to tighten the plastic. We do that by driving a stake into the ground 4 feet from the last hoop at each end of the low tunnel and tying a rope to each end of the plastic. We then pull as tightly as we can on both ends and secure the ropes to the stakes. That makes the plastic cover taut lengthwise. We then shift the sandbags on top of the edges of the plastic to make it taut from side to side. In heavy snow areas, if you are using plastic conduit, you should space the hoops 2½ feet apart.

Using sandbags to secure the edges is much faster and much less work than burying the edges, although it’s not as permanent. With sandbags, the covers can blow off in a really strong wind, but once winter arrives and everything freezes to the ground, nothing is going to move. The sandbags also allow us to cover every pair of beds side by side across a field because there is no need to find room to dig a trench and throw the soil aside as one needs to do when burying the edges.

We also use quick hoops in late fall on a temporary basis to protect outdoor beds of late crops. For example, we now plant even more of our popular August-sown carrots because we know we can harvest them fresh from the cool soil for an additional two weeks. When temperatures below 25°F or an early snowstorm are predicted we can rapidly erect quick hoops and cover them with a layer of clear plastic held down by sand bags. We remove the protection progressively as we harvest the beds.

Onions grown from seed sown outdoors in early spring. After the onion harvest, the same land is planted to winter crops before being covered by the greenhouse.

When spring arrives, we start ventilating these structures on sunny days. We remove a few sandbags along the southern edge and insert a notched prop to hold up the edges of the plastic and fabric. Once outdoor temperatures have moderated to the point where the fabric alone is protection enough (late March) we remove the plastic layers and store them until next winter.

Compared to the cost of a movable greenhouse, the economics of using quick hoops over suitable crops are very appealing. Quick hoops can be erected to cover 1,000 square feet (the size of a 22-by-48-foot greenhouse) for only one-twentieth (5 percent) of what it would cost to put up a greenhouse. Furthermore, the quick hoops used for overwintering can be disassembled and moved to cover other crops later in the spring. Quick hoops, because of their simplicity and long season of use, have completely replaced the curved wire wickets that we previously used to support fabric covers over our field crops.

With quick hoops as a low-cost cover, northern growers now have the opportunity to explore late-fall field planting of spring crops, a growing strategy that growers in warmer climates routinely use. However, in expanding this idea, northern growers need to consider these points:

• How early can fall-seeded crops be planted (to have them mature sooner in the spring) without triggering them to go to seed rapidly in the spring?

• At what size and/or stage of growth are young seedlings the hardiest for surviving through cold winter weather?

• What crops can be sown just before the ground freezes (late November/early December in our area) to winter-over as seeds and germinate extra early in the spring?

We conduct trials every winter to try to answer these questions, and we find the third one the most fascinating. Even here in the far north, why shouldn’t we sow seeds of peas or carrots or beets or arugula or onions or any number of other hardy crops in late fall for mid-February to mid-March germination? That would put a lot of the remaining hidden farm into production. The seeds might just sit there until conditions began warming in February, but even so, they would be established up to two months before we could get on to the soil for spring planting. We know the concept is sound because we sow carrots during late December in our cold houses and they germinate in a month. According to published tables of seed-germination rates at different temperatures, there are many crops for which this would certainly be possible. We are especially excited by the potential of this practice because we have recorded temperatures as high as 55°F inside the double-covered quick hoops on sunny days in the middle of February. Every day more new ideas for crops and techniques are suggested by what already exists. The winter harvest would appear to have endless potential for all of us involved in exploring it. We are just beginning to tease out the possibilities.