12 Month Food Production Using Unheated Greenhouses
Creates Profit, Jobs and Secure Food Supply
By Jon Kennedy
Roughly 15 percent of all fruits and vegetables consumed in the United States are imported from outside our borders. (1) This creates both a cash drain to local economies and a potentially unprotected vector for injection of disease into our food supply.
Growing fresh vegetables profitably in all regions of the United States during every month of the year is possible. Eliot Coleman has been perfecting the process for several decades, and now he is sharing his methods with the rest of us. Access to a library of historical observations, a working farm acting as a personal laboratory and much experimenting have resulted in affordable techniques for growing crops year-round in a manner which creates local employment and helps end “food deserts”
During the colder winter months, vegetable produce must be shipped from states and countries with warmer climates. Vegetables shipped long distances must be picked green so that the products do not spoil during transport. Since the nutritional content of unripened vegetables is substantially diminished, locally grown vegetables are preferable but not always available.
Unless local food supply is fostered, our nation faces rising food prices driven by the rise in transportation costs for that food. Local farmers who grow only during the traditional warm months also have a tendency to lose their market on the “back side” of the growing season when relationships with customers are severed for months at a time. During times when farms are not in full production, farm crews can find themselves unemployed. When the traditional non-growing months come, farmers tend to be short on income sources during periods with no harvest.
With proper financing and understanding of winter farming methods, a person with a farmer’s heart and entrepreneurial spirit can address many of these problems.
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Eliot Coleman has over 40 years experience in organic farming and has written about it since 1975. From his experiences Mr. Coleman has taken an analytical approach to optimizing productivity and minimizing risk. The findings have been documented in the books he authored, which include The New Organic Grower, Four Season
Harvest and The Winter Harvest Handbook. These publications serve as manuals that record applicable experiences and lessons learned. Topics include crop descriptions, required tools, planting schedules and applicable techniques for harvesting all year long. (2)
It takes six people to do all the growing, harvesting, selling, and delivering on his one and one half acres of intensive vegetables during full production in the summer. In the middle of the winter, one to one and a half people can keep up with it. (3)
According to historical research, six people for one and one half acres was exactly the same staffing for intensive vegetable production in Paris in 1850. Mr. Coleman added that the economics of this would be better with only four people which is why he is continually working to develop labor saving tools to make his farm more efficient. (3)
According to Mr. Coleman, when it comes to winter gardening there are several misconceptions. For instance, not all crops need summer-like temperatures to thrive. While tomatoes may prefer higher heat, some vegetables like spinach and lettuce produce exceptionally well during the cooler seasons. Another common misbelief is that hours of sunlight are too short to allow growth. Mr. Coleman teaches us that it is not the total hours of sunlight per day that matters as much as the total number of hours of daylight from planting until harvest. During shorter periods of sunlight, crops do take longer to mature from seed to harvest, but proper planning across a wide range of dates can compensate for this extra time, allowing 12 month harvest. (3)
The farm sticks to three main principles to guide its operating philosophy: simplicity, low external inputs (including energy) and high quality outputs. By making the most effective use of this operating basis, Mr. Coleman has succeeded in creating an effective system during a season when plants are usually dormant. The simplest technology is used to generate an effective economy of scale that lengthens fresh vegetable crops through winter months, while providing local 12 month employment. (3)
The main objective is to harvest at least three crops per year from every square foot of the cold houses; two harvests in the long Maine winter and at least one in the summer. To increase the farm’s effectiveness during these unforgiving winter months, Four Season Farm strives to pick vegetables that have the greatest tolerance to cold temperatures, adheres to a strict schedule for planting and harvest, and ensures vegetables are under constant cover when the cold weather dictates. (3)
On the Four Season Farm there are three main building types in use: hot houses (heated greenhouse for starting seedlings), cold house (unheated greenhouse in winter) and a cool house (slightly heated with natural gas only to prevent the vegetable washing system from freezing). The vast majority of the vegetables Mr. Coleman produces during the winter are grown in the cold houses that use no supplemental heat. Decisions about how often to supplement with external sources of heat depend on the market price of fuel. (3)
When Mr. Coleman initially approached local stores and restaurants in the mid-1990s about selling his crops, his necessary sale price was considerably more than similar vegetables shipped from warmer climates. Valuing the superior quality of his greens, customers justified the higher price. At each of the businesses, his vegetables sold out in one day. Since that time Mr. Coleman’s methods and efficiencies have improved and operating costs have continued to drop. For the year-round farm to be financially viable, the food prices must be both affordable and fair. Mr. Coleman notes the farm’s price must be “sufficient to make a decent living -- without [the farmer] being accused of being elitist or unfair.” (3)
During winter production, the farm sets a target of $5 saleable product per square foot for its 12,000 square feet of available greenhouse space. The cool house target is $10 saleable product per square foot. (By comparison, large heated commercial flower-growing greenhouses yield about $15 per square foot, but have much higher energy cost.) (4) The unheated greenhouses produce three crops per year. Being slightly warmer, cool houses can accommodate 6 crops per year. This detailed tracking system allows the farm to determine which vegetables return the greatest economic value. Combining the field and greenhouse crops, the gross income is $80,000 per acre per year!
Establishing efficient and productive farms that operate year round allow for consistent relationships between the customers and farmers and provide year around employment. Once customers know they can depend on the farmer for healthy, sustainable produce year-round, that relationship deepens. As winter producing farms become more prevalent, the corresponding sense of food-based community available to each of us strengthens, national security increases, local jobs are created, and money that used to go out of the country remains in the local community.
Even though agriculture has been an underpinning of civilization for millennia, the number of variables out of the farmer’s control remains numerous. Issues like air temperature, precipitation, relative humidity, pests, disease and the like are vital factors in determining a farms success (or demise). As farmers like Eliot Coleman objectively analyze vast amounts of data to optimize systems that can be controlled, the fact remains our existence will always be somewhat chaotic. What Mr. Coleman has done is use his imagination, modern materials, and data, to create a reproducible process for generating vegetables in climates most of us presumed were not capable of 12 month food production.
Four Season Farm
609 Weir Cove Road
Harborside, ME 04642
Four Season Farm is open to the public during farm stand hours. Check the website for details.
Banner Green Houses (Banner, NC) - http://www.bannergreenhouses.com/
Pertinent Video Clips:
- Coleman, E. (2009).Winter Harvest Handbook
- Personal Communication, Mr. Coleman, February 2011