JUNE/JULY 2009
Sustainability is a Four Letter Word Interview with Martin Melaver
Makenna Goodman
Transition Towns
Six Transitions Conversations that Matter
Shaktari Belew
Receiving the Gift of Change
Crystal Arnold
Homegrown Grains
The Key to Food Security
Gene Logsdon
The Winter Harvest
Eliot Coleman
Solve Health Care and Climate Change by Changing our Food System
Amy Goodman
Doctors Warn:
Avoid Genetically Modified Food
Jeffry Smith
Wilderness Rites for Elders
Jody Woodruff
Cosmic Calendar
Salina Rain
The Winter Harvest
By Eliot Coleman
Choosing locally grown organic food is a sustainable living trend that’s taken hold throughout North America. Celebrated farming expert Eliot Coleman, a passionate advocate for the revival of small-scale sustainable farm-ing, helped start this movement with The New Organic Grower published 20 years ago. He continues to lead the way, pushing the limits of the harvest season while working his world-renowned organic farm in Harborside, Maine. Coleman’s latest book, The Winter Harvest Handbook, provides a practical model for supplying fresh, locally grown produce during the winter season with clear, concise details on greenhouse construction and maintenance, planting schedules, crop management, harvesting practices, and even marketing methods. The following excerpt is just a taste of what you will find in this valuable book which will be appreciated by small farmers, homesteaders and experienced home gardeners who seek to expand their production seasons.
)ur story begins with the winter season and the return of the sun. The crops we sell during the winter are not leftovers from traditional summer cultivation. They are, rather, part of a cycle of year-round production that emphasizes different crops in their respective seasons. Winter is the unique season of this uncommon small-farm model, and from our experience offers potential for successful production wherever you live.
Any claim about winter production of fresh vegetables in a cold climate with no heating or heat-storage systems seems highly improbable. One only has to glance outside in January to see how ragged or dead the plants in fields and gardens look. However, it’s a misconception that all vegetable crops need summer-like temperatures for best growth. As inhospitable as cold temperatures may be for warm-season crops like tomatoes, that is not the case with those vegetables like spinach and lettuce or claytonia and mâche that prefer to grow in the cool seasons. Not only do many of them tolerate cold conditions and even temperatures well below freezing (as long as they are spared the desiccating effects of cold winter winds), they actually thrive and are sweeter, tenderer, and more flavorful.
In addition to the concern about cold temperatures, a second misconception about winter growing is that day length is too short. Many people believe that sup-plementary lighting will be required. However, short winter-day length is not the barrier it appears to be. Crops do take longer from seed to harvest, but earlier succession planting across a wider range of dates can compensate for that reality. Most of the continental US receives far more winter sunshine than parts of western Europe where, owing to milder temperatures, there is a long tradition of fresh winter vegetables.
Planting crops in a heated greenhouse has always seemed the obvious solution for growing vegetables during the winter months. The old-time heated greenhouses for vegetable production were commonly called “hothouses.” They were used for tomatoes at a minimum night temperature of 65°F (18°C) or lettuces at 55°F (13°C). An un-heated greenhouse was considered un-usable in cold winter climates, except as a storage area for hardy potted plants. Our successful experience with winter production proves that this is not so. We call our unheated greenhouses “cold houses” in contrast to “hothouses.” In our cold houses there are many leaf and root crops that can be successfully grown and/or maintained all winter long.
Our economical cold houses are the end result of the quest we began in 1970 for simple, low-cost, user-friendly winter production. These unheated greenhouses are completely passive, much more so than the complicated and expensive “solar” greenhouse designs of the ’70s. There is no heating system, nor any water or stone ballast with pumps or fans as a heat-storage medium, nor is there buried insulation around the perimeter. We followed our minimalist preferences and avoided any space-age materials, complicated technologies, or whizzing machinery with which we are not comfortable.
The winter harvest, as we practice it at Four Season Farm, has three components: cold-hardy vegetables, succession planting, and protected cultivation.
Cold-hardy vegetables are those that tolerate cold temperatures. They are often cultivated out of doors year-round in areas with mild winter climates. The majority of them have far lower light requirements than the warm-season crops. The list of cold-hardy vegetables includes the familiar—spinach, chard, carrots, scallions—and the novel—mâche, claytonia, minutina, and arugula. To date there are some thirty different vegetables—arugula, beet greens, broccoli raab, carrots, chard, chicory, claytonia, collards, dandelion, endive, escarole, garlic greens, kale, kohlrabi, leeks, lettuce, mâche, minutina, mizuna, mustard greens, pak choi, parsley, radicchio, radish, scallions, sorrel, spinach, tatsoi, turnips, watercress—which at one time or another we have grown in our winter-harvest greenhouses. The eating quality of these cold-hardy vegetables is unrivaled during the cooler temperatures of fall, winter, and spring. They reach a higher level of perfection without the heat stress of summer.
Succession planting means sowing vegetables more than once during a season in order to provide for a continual harvest. The choice of sowing dates, from late summer through late fall, and winter into spring, keeps the cornucopia flowing. In midwinter the vigorous regrowth on cut-and-come-again crops provides the harvest while late-fall-and-winter-sown crops slowly reach productive size.
We begin planting the winter-harvest crops on August first, the start of what we call the “second spring.” We continue planting through the fall. The reality of sowing for winter harvest is that the seasons are reversed from the usual spring-planting experience. Day length is contracting rather than expanding; temperatures are becoming cooler rather than warmer. Success in maintaining a continuity of crops for harvest through the winter is a function of understanding the effect of shorter day length and cooler temperatures on increasing the time from sowing to harvest. Thus the choice of precise sowing dates for fall planting is much more crucial than for spring planting. The dates are also very crop specific.
We aim for a goal of never leaving a greenhouse bed unplanted, and we come pretty close. Within twenty-four hours after a crop is harvested, we remove the residues, re-prepare the soil, and replant. We keep careful records so as to follow as varied a crop rotation as possible.
Protected cultivation means vegetables under cover. The traditional winter vegetables will often survive outdoors under a blanket of snow. Since gardeners can’t count on snow, the best substitute is shelter of an unheated greenhouse. Many delicious winter vegetables need only that minimal protection. Our winter-harvest cold houses are standard, plastic-covered, gothic-style hoop houses. The largest of our houses are 30 feet wide and 96 feet long. They are aligned on an east-west axis. For the most part the cold houses need only a single-layer covering of UV-resistant plastic, whereas heated greenhouses benefit from two layers, which are air-inflated to minimize heat loss.
The success of our cold houses seems unlikely in our Zone 5 Maine winters where temperatures can drop to –20˚F (–29˚C). But our growing system works because we have learned to augment the climate-tempering effect of the cold house itself by adding a second layer of protection. We place floating row-cover material over the crops inside the greenhouse to create a twice-tempered climate. The soil itself thus becomes our heat-storage medium, as it is in the natural world.
Any type of lightweight floating row cover that allows light, air, and moisture to pass through is suitable for the inner layer material in the cold houses. The row cover is supported by flat-topped wire wickets at a height of about 12 inches (30 cm) above the soil. We space the wickets every 4 feet (120 cm) along the length of 30-inch-wide (75 cm) growing beds. The protected crops still experience temperatures below freezing, but nowhere near as low or as stressful as they would without the inner layer. For example, when the outdoor temperature drops to –15˚F (–26˚C), the temperature under the inner layer of the cold house drops only to 15˚F to 18°F above zero (–10˚C to –8°C) on average. The cold-hardy vegetables are far hardier than growers might imagine and, in our experience, many can easily survive temperatures down to 10˚F (–12˚C) or lower as long as they are not exposed to the additional stresses of outdoor conditions. The double coverage also increases the relative humidity in the protected area, which offers additional protection against freezing damage. The climate modification achieved by combining inner and outer layers in the cold houses is the technical foundation of our low-input winter-harvest concept.
In a world of ever more complicated technologies, the winter harvest is refreshingly uncomplicated because all three of these components are well known to most vegetable growers. What is not well known is the synergy created when they are used in combination, and that is what we continue to explore on a daily basis on our farm.
Mobile Greenhouses
We have added one new twist to a winter-harvest system by reviving an old European practice—the mobile greenhouse.
According to the best historical information I can find, the first mobile greenhouse was built in 1898 in England. Even though it was a large glasshouse, it could be moved safely because railroad wheels running on steel rails supported its iron framework. We have copied the mobile greenhouse concept, but on a far less expensive scale.
The mobile greenhouse offers a number of advantages. First, it allows us to avoid the expense of having to cool the house when starting our winter crops in August. Instead, we sow winter crops out of doors in the field over which the greenhouse will move. Meanwhile the greenhouse continues to provide protection for heat-loving crops such as tomatoes, peppers, cucumbers, eggplants, melons, or sweet potatoes. We leave the greenhouse over the summer crops until the summer crop season is finished, sometime in mid to late October here in coastal Maine. Then, we move the greenhouse to cover the winter crops. The following October, the same process takes place in the reverse direction. (In hotter climates like northern California and southern Oregon use of mobile greenhouses or individual hoops over beds may be used for supporting shade cloth to protect the young plants before the winter covering of polyester spun cloth or plastic is put in place, Ed.)
A second advantage of the mobile greenhouse is the avoidance of the buildup of pests, diseases, and excess soil nutrients, which can be problems in a permanent greenhouse. For one year out of every two, our growing beds are uncovered, exposing the soil to the cleansing powers of sun, rain, wind, and snow. As an additional advantage during the initial soil-building years, the uncovered year allows us to plant a long-term, deep-rooting, leguminous green manure crop on that section. This green manure can occupy the soil of the uncovered site for as long as thirteen months (June through the following July), if you forgo a summer vegetable crop, or ten months (September through July) if you sow the green manure toward the end of the summer-crop season. The benefits of green manures for protecting, enriching, and aerating the soil were an important part of our soil-fertility-building program in the first few years. All green manures should be turned under three to four weeks before the planting date of the crops following them.
Minimal Supplementary Heat
From the beginning of our commercial winter production we have had one large greenhouse equipped with supplementary heat. To distinguish this from our unheated cold houses, we call this a “cool house.” We built the cool house because we knew a greenhouse would be the least expensive type of covered area for washing and packing our produce. One-quarter of the house has a concrete floor with space for our washing and packing facilities, our walk-in cooler, and for starting seedlings in the spring. Since we need to prevent our vegetable washing system from freezing in the winter, we installed a propane heater. The thermostat is set low, just above 32˚F (0˚C).
The remaining three-quarters of this house is used for growing winter crops. This was our laboratory for exploring the parameters of minimal heating. We learned that keeping this house just above freezing at night accelerates plant growth enough that we can harvest two more crops per winter than in the unheated houses (an average of five to six crops per year as opposed to three to four). When heating-fuel prices were low, one extra crop could pay for the cost of the propane to fuel the heater, so we came out ahead financially. We also discovered that with supplementary heat it is possible to keep highly popular crops like baby turnips and crisp radishes available all winter, whereas the freezing in the unheated houses limits their production. We could also bring our eagerly anticipated early spring carrots to harvest six weeks earlier (April 1) than in the unheated houses (May 15).
If a fuel source (such as wood) is cheap enough or local enough so that one additional crop can pay for the cost of minimal heat, simple economics suggests that we should add heat in all our houses. And indeed, the benefits we discovered, in addition to the possibility of getting an earlier start on warm-weather summer crops, convinced us to experiment with minimal heat for several years. However, the original inspiration for the “winter harvest” was to see what we could achieve in winter without the complications and resource consumption of heating. Our success in the cold houses has been most gratifying, and they continue to be more than adequate for baby-leaf salads and braising mixes, spinach, leeks, Asian greens, winter carrots, and the spring crops that follow them. We continue to pursue the goal of doing as much as possible with unheated houses. Even though we have decided not to pursue the cool-house option further, I include information from our experience for those growers who may find the idea appropriate to their operation. For growers in warmer climates than ours, the unheated houses will be all they need.
Excerpted with permission from The Winter Harvest Handbook (Chelsea Green). Visit www.chelseagreen.com for many excellent books on gardening and agriculture.
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Eliot Coleman |
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Gardening |
