The Greenhouse and Hoophouse Grower’s Handbook: Organic Vegetable Production Using Protected Culture

review by Richard Robinson, farm@hopestill.com

I try to start my tomatoes extra early, and know I risk inducing “transplant shock” in some portion of them when I begin transplanting into my unheated hoophouse in mid-April. This spring, with the first batch I was scrupulous about covering them at night with several layers of row cover, but got a bit lazy with the later transplants, because after all it was already May and I was growing inside, so really, they should be fine. Here in southern New England, the entire month of May was cold and cloudy, and although they survived, still to this day (I am writing in mid-July) many of those later transplants haven’t taken off—they are thin, knotty, and stunted, and sporting early fruit clusters that will be their downfall, unless I snip them off. Meanwhile, the tomatoes I transplanted the earliest, and pampered through their first several weeks in the ground, are taller than I am and bearing gloriously.

Andrew Mefferd has written a book that explains exactly what happened—why I succeeded with the early group and failed with the later ones, and how I might have avoided failure by preventing the temperature swings my poor later transplants suffered. Early chilling sends tomatoes (and many other plants) into a “generative” mode, concentrating on setting fruit at the expense of growing the vegetation to support it. Steady—and high—temperatures early in life promote a more “vegetative” mode, exactly what my early transplants got, snug under row cover for the first several weeks of life.

“The Greenhouse and Hoophouse Grower’s Handbook” explains how those of us growing in “protected culture”—a term encompassing both heated and unheated structures—can get the most profit out of our houses by growing eight high-value crops—tomatoes, peppers, eggplant, cucumbers, and “the leafy crops—and manipulating their environment: temperature, humidity, and even CO2 levels—to maximize their yields.

Mr. Mefferd has the background to present this information with authority. He is a grower himself, in Maine, and for seven years conducted greenhouse variety trials for Johnny’s Selected Seeds. He has also extensively toured high-production growing houses, especially in the Netherlands, which, tiny though it is, is the world’s largest exporter of fresh vegetables. Those eggplants you eat in April probably come from Holland.

The book provides some basic information on the structures themselves, but newcomers will want to look elsewhere for more details on siting, choosing a design, and erecting their first house. Instead, Mr. Mefferd goes deep into the details of propagation, grafting, transplanting, and most especially, environmental control.

For any hoophouse or greenhouse grower, the book contains a wealth of practical information that is likely to increase your profits if you apply it. For instance, I didn’t know that diffused light is superior to direct sunlight, because it provides more light to lower leaves, and can keep upper leaves cooler, increasing photosynthesis for both. Plastic films with greater diffusivity may be superior to glass in this respect. A light ground cover, such as white plastic or straw, will also spread out incident light and increase productivity.

For those interested in trying their hand at grafting, or are wondering what all the fuss is about, there is an entire chapter—26 pages—on the why’s and especially the how’s of grafting tomatoes, and a bit on other crops as well. “Grafting is the most important development in tomato growing since the commercialization of tomato hybrids in the mid-twentieth century,” he writes, for the benefits it can bring in yield and disease resistance. After reading the chapter, you would probably be ready to try your hand at it, if you had a mind to.

Temperature control is at the heart of the highly productive Dutch system, and is a major focus of Mr. Mefferd’s book as well. He provides an extensive discussion of the effects of different temperature regimens, and the benefits of control, the tighter the better. For tomatoes, seeds germinate best at 80-82 F. Seedlings grow best at a flat 67 F, which should be elevated to 73 F for the week after transplanting, to promote vegetative growth. Once production begins, daytime temperatures should be 75 F, and nights 65 F. Once in full swing, daytime temperatures should be a few degrees higher. And if those temperatures seem low to you, well, Mr. Mefferd explains why they aren’t. He also provides interesting ideas about manipulating temperature to “steer” plants toward more vegetative or more generative growth modes.

Hoophouse growers will immediately recognize the challenge of this degree of control; in a house without supplemental heat, the nighttime low is often close to or at the outside temperature. Mr. Mefferd recognizes this challenge; indeed, he is a hoophouse grower himself. Nonetheless, the tomato wants what the tomato wants, and it behooves us as growers to know what it wants, even if we can’t supply it perfectly.

This gap between the ideal and the practical for those growing without heat leads me to my only real criticism of the book—I would have loved to see the author directly address the sometimes enormous differences between hoophouse and greenhouse growing more often and more directly, and to spend more time addressing the needs and challenges of us hoophouse growers explicitly, rather than (as one can certainly do) having to tease out one’s own solutions from the information provided. “Protected culture” is a good phrase, but there are some fundamental differences between heated and unheated structures that it glosses over. Perhaps in the next edition, Mr. Mefferd might provide us more guidance, or perhaps I just need to read the book through once more—it certainly has the depth of information to justify a second or third reading.

The book also doesn’t address in much detail the issues that heating a greenhouse in New England raises, both financial and environmental. This is perhaps understandable since the cost/benefit calculation depends on both local conditions and personal values, but it leaves the grower without any practical guidance for making that calculation on their own.

Is this book for you? It should be, if you grow in a greenhouse or a hoophouse, or hope to. You are likely to learn a few things, probably many things, you didn’t know before, and it will likely repay its cover price and your reading time many times over. I will still be pushing the season with early tomatoes, but next season I will be spending much more time pampering all my transplants, well into the spring.