Yes, it is that awful time of year when we step out after the first hard frost and see the tomato vines and other susceptible plants all dark green and shriveled under a crystalline layer of new frost. Winter has begun the slow occupation of our gardens, and we have nothing to look forward to but our canned vegetables and the beautiful pictures of growing plants in the seed catalogues.
Maybe. I recently had the fortune (misfortune due to the amount of work I went through?) of coming across a Craigslist find of an attached greenhouse. The overly wealthy purchaser of a home did not like the attached greenhouse, with all of it’s automatic fans and heater and posted it for a song on Craigslist. I just happened to call, and after paying less than 1/10th the retail price, and subsequently drilling out 100 or so rivets over 2 days, it is sitting in my yard unassembled, but marked and ready for installation. It was relatively new, so I could order the few new parts I needed from the manufacturer.
This was a very blessed find, but after thinking about it, this small greenhouse would be great for starting seedlings, and if I really worked at it, I might be able to grow enough vegetables for a couple weeks of food for our family of 4, but only after spending a small fortune to heat it throughout the coldest days of the winter and maybe even using some supplemental lighting.
I realized the best option for this greenhouse is to use it to start my heat-loving plants early in the season, growing heirloom, non-GMO plants from seed, and thereby avoid the big box chains for my young plants for next year’s garden. Still, it was not a bad investment overall. I plan to start my seeds, and possibly work with some local friends by supplying them with heirloom seedlings in pots they can not get anywhere else for next year’s gardens.
But what about actual fresh vegetables in the winter? For that, we need to reference the amazing work The Winter Harvest Handbook by Eliot Coleman. Coleman lives in Maine. He uses unheated greenhouses. In the winter. He grows an amazing collection of vegetables. The only veggies he really avoids are heat lovers like tomatoes, cucumbers and peppers. Oh, and he does not mention it in the book as far as I’ve read, but in a closed greenhouse, you have to pollinate those by hand, with a paintbrush.
Here is how his system works: You pick your veggies appropriately (a lot more are available than you think). A single coat of greenhouse plastic and the thinnest row covers. By adding a covering of plastic over your hoop house, you move your zone 1.5 zones to the south. By adding a row cover, you add another 1.5 zones. That means in my area of Virginia, I can grow whatever they are growing in Florida or California during the winter.
The row covers float over your veggies and allows the sunlight to pass through to the plants and soil. At night, moisture condenses on the under side of the row covers reflecting the long wavelength heat radiation coming up from the soil and bouncing it back down. No double walled plastic over your hoop house, no constant fans to keep the layers separate, and no supplemental heat. The other “ah ha” moment this book suggested was that a cold winter greenhouse is not really for starting the harvest, but extending it. Additionally, there was a time when this Maine greenhouse setup did more business in the winter than in the summer; not only in volume, but also probably from lack of competition. More pictures and information can be found on his Four Seasons Farm website.
This is not a book review blog really, so let's get back to our self-sufficient family application. You have a couple ways to look at this. You can use it to produce food for your family and then additional food to sell / barter. The greenhouse can remain and be used to start your heat loving vegetables, and then the plastic removed when it starts getting hot enough to sustain them. You can then add the plastic back at the end of the growing season to maintain those peppers and tomatoes for a couple more weeks. The hoops can be used to hang strings to keep your tomatoes and other vines vertical. You can even wrap the base with chicken wire if you need to keep out certain pests.
Locally, Coleman sells a significant amount of cut and come again vegetables throughout the winter – spinach and lettuces, in addition to other veggies. Using this setup, you could technically have a winter farmer’s market. Your local restaurants could use your produce to continue to advertise that they use locally sourced vegetables (where do you think they normally get salad lettuce in the middle of winter?) Apparently, winter-grown vegetables taste better. Real or perceived, it was Coleman’s consistent feedback.
As soon as I finish my current attached greenhouse project, I’m going to look at erecting my hoophouse. To get started, first look at www.craigslist.org or www.searchtempest.com to search your area for used greenhouses. If there is nothing available, or you want to customize your options, you can check out Build It Solar's Sunspaces page for lots of resources, many of which are free. In considering short and long term expenses and usability, my personal favorite was the bender on Lost Creek's website. This site sells very affordable bending jigs to use chain link fence pipes as the frame for hoop houses. Several folks have also used this bender to build semi-permanent outbuildings as well (check out the customer gallery).
My last thought was on the plastic. Usually, regular polyethelyne plastic is not recommended for greenhouses due to its lack of UV protection. However, I wonder if used only for winter, would it last for more than one season? Maybe. However, I saw some pretty conservative prices on greenhouse plastic on Ebay. Your best money spent though is on Coleman’s book. It’s an easy read, well documented with the science behind his suggestions. It contains lists of vegetables, planting times to maturity based on your zone and type of cold greenhouse, and lots of supplemental information. Bon appétit!