Imagine having a single portable hoop house that you could use in winter to grow crops and start seedlings, and then employ again in summer to safely keep chickens on pasture. Using just one piece of equipment to accomplish these tasks and more is the goal of our new Modular Grow Dome design, a collaboration between MOTHER EARTH NEWS and our company, Four Season Tools.
Inspired in part by the ever-innovative work of Maine market gardener Eliot Coleman, we’ve outlined several options for building a sturdy, movable modular greenhouse for year-round gardening. From these options, you can choose the best fit based on whether you need a small unit for your backyard or want to connect a series of domes to extend the season for larger-scale vegetable production. You can round up all the parts for these designs yourself, or let us gather everything you’ll need by purchasing a kit, which can be shipped via UPS or FedEx (see “Resources” later in this article).
The hoop houses are engineered in 12-foot and 15-foot widths and are fitted with bracing, “ski tips” and anchoring, so they’re easy to move manually and simple to secure after being positioned.
Most greenhouses on the market aren’t mobile. Plastic-film hoop houses, also called “high tunnels,” are used primarily by market farmers and are large and stationary. Smaller glass or rigid-plastic greenhouses are often expensive and aren’t designed to be moved. Our Grow Domes are easily portable, however, and their movability is key to the units being suitable for multiple functions, including large-scale vegetable production. Mobile domes help mitigate problems with pest and disease buildup common in stationary greenhouses. They can rotate with your crops or provide a predator-resistant place to pasture poultry. The kits also allow for flexibility in size, so a unit can meet specific zoning size limits or be considered “temporary” on urban or residential lots subject to building restrictions. The domes on our City Bitty Farm in Kansas City, Mo., for example, are less than 200 square feet, which is below the city’s requirement for a building permit.
Our dome frames are made from off-the-shelf steel pipe and fittings commonly used for chain-link fences. In addition to the framing, the kits include 6-millimeter, UV-resistant greenhouse film as well as special hardware and channels with spring wire that make it easy to install and replace both plastic and shade cloth as needed.
Greenhouses are good for growing plants mostly in fall, winter and early spring. Pens for raising pastured broilers are necessary for only a few weeks in summer or fall. The Modular Grow Dome anticipates both uses. The plastic covering transmits plenty of light for plant growth, and if you use the unit to keep hens for eggs in winter, solar heat gain will keep the birds warm on sunny days. In spring, you could start seeds at the same time you brood some chicks. In summer, you can either move the unit into a shady area for poultry or replace the plastic with a shade cloth, all while experimenting with heat-loving summer crops.
If you plan to use your dome for chickens, you should make it predator-resistant. Double-walled corrugated plastic — instead of greenhouse plastic — will keep predators out, but it’s quite pricey. Lining the inside of the dome with wire fencing or hardware cloth (both readily available at hardware or farm stores) is a more affordable alternative. Depending on how much predator pressure you have, you could also install some wire flaps around the perimeter to deter digging.
As a single-unit hoop house, the 12-foot-wide dome provides space for three 30-inch beds separated by 1-1/2-foot-wide walkways. We also offer a 15-foot width for four 30-inch beds separated by 1-1/2-foot-wide walkways. If you want more growing space, you can hook two or more units together using our 4-foot-long connector piece. You can use your units separately during the warmest months when protected growing space may not be necessary, and then combine them as temperatures drop to create a spacious winter growing area. Long structures known as “caterpillar tunnels” are common for larger-scale vegetable production, but connecting multiple movable domes is a more flexible option that will allow you to reconfigure and relocate as needed, at a dramatically lower price per square foot.
With such a cozy interior, you’ll be able to bring chickens to your farm earlier in spring. The unit provides refuge from the elements and can easily be moved from place to place by two to four adults or a small tractor. Such a setup lets you give birds new grazing ground at a moment’s notice. With this extra space and protection, market farmers could raise chickens year-round to sell eggs and meat.
Our 15-foot-wide unit can provide even more protection from cold if combined with the low tunnels popularized by Eliot Coleman. Low tunnels are commonly constructed from 10-foot pieces of half-inch electrical conduit bent into half-circles, giving growers 6-foot-diameter tunnels that are 3 feet high. One low tunnel will cover two 30-inch-wide beds. So, in the slightly larger 15-foot-wide version, you’ll gain increased growing space plus the ability to install two low tunnels side by side, covered by fabric row cover (see photo in the Slideshow above). Coleman has discovered that placing these low tunnels inside a greenhouse furnishes your crops with temperatures that mimic those of nearly one full hardiness zone south of your location.
Adequate ventilation is essential to avoid overheating within the domes. The end-wall design is a critical part of the ventilation strategy. Our design includes two end-wall choices: low-cost “scissor doors” that allow both ends of the hoop house to open as needed, or square, steel, prefabricated end walls sized for screen doors. You can cinch up the plastic on the sides of longer buildings on hot days to allow for airflow.
For all movable buildings, stability in wind and snow is an important consideration. A Modular Grow Dome unit is held down by two T-posts at each corner. The posts are installed in opposing directions through welded rings bolted to the ski tips on the skids (see photo in the Slideshow).
You could use your Modular Grow Dome as a shelter for ducks, turkeys or, with some reinforcing, larger animals, such as goats or pigs. Perhaps you need a warm spot to store compost to keep it thawed and ready for early spring use. Or maybe you’re imagining a warm, moisture-free place to plant seed flats, cure crops, dry seeds or store hay. These space-saving, simple and versatile units offer endless possibilities for backyard gardeners as well as large-scale market farmers.
Four Season Tools’ new “Chickshaw” unit debuted at the MOTHER EARTH NEWS FAIR in Lawrence, Kan., last fall. This rickshaw-like, two-wheel coop provides portable housing for a small flock of broilers or laying hens. In addition, the coop slides off its cart easily, making it a snap to move a series of coops to fresh grazing locations, plus giving you the convenience of a spacious 6-by-6-foot or 6-by-8-foot garden cart for moving seedling flats and performing other tasks.
Both the Modular Grow Dome and the Chickshaw will be at the Four Season Tools booth at the MOTHER EARTH NEWS FAIR on Oct. 25 and 26 in Topeka, Kan. For more information on all of our Fairs, head to the MOTHER EARTH NEWS FAIR site.
A video about constructing the Modular Grow Dome is available in How to Build a Modular Grow Dome. Four Season Tools has a free online catalog that offers the Modular Grow Dome kit as well as other agriculture products, including low tunnel benders, row covers, and larger movable greenhouses and coops. The Modular Grow Dome kits include pipes, bracing, fittings, plastic and instructions. Several options are available, but basic kits without the T-posts or 6-millimeter plastic come in two sizes: 12 by 12 feet for $765 with stationary ground posts, or $825 on skids; or 15 by 12 feet for $875 with ground posts, or $935 on skids. A 15-by-140-foot building (nine domes with eight connectors) costs $4,875 with ground posts, or $5,395 on skids.
Four Season Tools founders Greg Garbos and Mike Bollinger re-imagine scale-appropriate systems for year-round food production with innovations in movable greenhouses and season extension. Greg lives with his family on City Bitty Farm in Kansas City, Mo., and Mike and his family live on River Root Farm in Decorah, Iowa.
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