Gardening methods around the world vary immensely, because the soil, air temperatures, wind patterns and other factors differ greatly. The need to cover a gardening area is usually because you want to protect your garden from animals, but it’s often because you want to extend your growing season or protect your plants from a cold environment. Fences and other means are typically pretty effective for preventing pests from nipping your buds, but protection from the cold means building a greenhouse.
In northern climates or higher elevations where it gets very cold, a greenhouse is a good way to extend your growing season and possibly provide you with year-round food. Considering that a greenhouse enables you to lay your seeds earlier and lets your garden produce later in the year, a greenhouse is well worth looking into.
Garden and farm suppliers have the resources and equipment today to construct the best high-tech greenhouses for home and commercial operations. Nearly all farms and nurseries these days have at least one greenhouse, and they might have several.
If you’re a beginning gardener and just getting started growing things, you probably don’t need a greenhouse yet. For starters, you should learn what plants grow well in your area, and you should take the time to understand how your local plants respond to the sun, shade, wind currents and temperature variations in general.
Once you’ve learned what grows well where you live and you’re satisfied with your experiments with various plant foods, you’ll get to the point at which you realize the limits of farming and winter’s effect on your productivity. This is when you might consider a greenhouse.
Before you get started on your project, it’s a good idea to check with your local government to find out if there are any restrictions, permits or other requirements associated with building the structure you’re planning.
The Frugal Farmer
Before you spend an arm and a leg on the components for a greenhouse, let’s look at some of the ways to create the greenhouse effect for as little money as possible.
During the Great Depression, my grandfather ran a 51-acre farm in rural Ohio. He had 3,000 chickens, an orchard, vineyard and a large area where vegetables and corn were grown. The Ohio winters were cold, and the snow was deep.
In order to get a jump on the spring planting, my grandfather had built a small, low-cost greenhouse for sprouting seeds. He used cinder blocks and mostly discarded glass windows to build the little greenhouse. My grandfather was a practical, pragmatic man, and he tried not to spend money if it wasn’t necessary. Bear in mind that this was during the Great Depression, when jobs were scarce.
The little greenhouse measured perhaps 8 feet wide by about 15 feet long, which is not huge by greenhouse standards. He began construction by laying out cinder blocks to define the perimeter. On top of this, he built a simple framework with 2x4s and a peaked roof that was tall enough inside to walk upright. He covered the framing with long glass windows, which I believe were discarded from a construction or renovation project. He added a simple door, and inside, there were low platforms in which he planted his seeds.
Such a greenhouse would shed the snow in the winter because of the steep roof, and it would retain some heat in winter as well, even with minimal sun.
Over the years, I have seen many greenhouses built with discarded windows; and, if they are built well, the air temperature inside is warm and conducive to sprouting seeds when it’s cold outside. Many of them have been variations of what my grandfather built so long ago, depending upon the builder’s needs and the materials that happened to be available.
The basic greenhouse is essentially an enclosed structure that allows light to get in, heat to stay in and has a door for easy access. Some larger greenhouses actually don’t even have a door, just an opening, because the doorway opening provides some ventilation for excessive heat.
The size of your greenhouse will be based upon your needs and your available space. You should site your greenhouse where there is full sun, but it might also do well if there happens to be some shade. Remember that the sun in the Northern Hemisphere is traveling across the southern sky, so the long side of your greenhouse should be facing the sun.
Because of space considerations, we once had a greenhouse that had to be located on the north side of a house, where there was minimal sun during the winter. This was a metal-framed greenhouse covered in plastic and barely big enough to stand in. It remained very warm, almost hot, inside during the winter.
A simple greenhouse can be created from the metal framework for a patio canopy or a pop-up tent. The metal framework is often discarded when the fabric canopy has begun to tear and degrade and can be rescued from the curb on trash days in your area.
If you cannot find such a framework, it’s still fairly easy to fabricate one using 2x4s and/or hollow pipes (such as electrical conduit or discarded PVC pipes). These materials are both lightweight and easy to join together. The ideal framework for a do-it-yourself greenhouse is a rectangular floor shape with a peaked roof. The peaked roof, although not absolutely essential, helps to shed leaves, rain and snow. You can secure the pieces together with connectors, screws, clamps or heavy-duty zip ties.
“CONSIDERING THAT A GREENHOUSE ENABLES YOU TO LAY YOUR SEEDS EARLIER AND LETS YOUR GARDEN PRODUCE LATER IN THE YEAR, A GREENHOUSE IS WELL WORTH LOOKING INTO.”
Create a simple and convenient door for getting in and out of the greenhouse with more of the same framing or wood. Cover the entire structure with plastic sheeting. The cheapest would be painter drop cloths from the hardware store. To reduce seams, use the largest size you can find (a thickness of 1 millimeter is sufficient). The seams can be sealed with clear shipping tape, duct tape or an appropriate adhesive if you prefer. Be sure the plastic is taut so it will be affected as little as possible by wind. Bear in mind that plastic sheeting will not last as long as glass or polycarbonate panels, so plan on repairing or replacing the sheeting every few years as needed.
Before you begin to build your greenhouse, consider the ease of entry and egress, because you want that to be convenient, especially when you’re lugging bags of soil, fertilizer or other awkward loads. Location and orientation to the sun, as with most structures, is very important.
Once your greenhouse is built, fill it with your tables or platforms, fill flats or pots with soil and plant your seeds.
It will be important to monitor the air temperature inside the greenhouse so it doesn’t get too hot. When this happens, simply keeping the door ajar might provide enough ventilation. But in those cases for which this solution is not practical (such as when animals might get into the greenhouse), create venting that can be opened and closed as needed. Venting can be as simple as a flap cut into the top part of the end walls just below the roof so the flap can be opened and closed as needed.
Some greenhouses in particularly cold areas have simple fireplaces built inside with a vent to the outside. This actually serves two functions: The vent works automatically to reduce heat from the greenhouse as it passes through the fireplace to the outside. Also, if it’s really cold — as in freezing temperatures — you could build a small fire in the fireplace to warm the air in the greenhouse.
One of the more popular styles of greenhouses that I’ve seen on farms and commercial nurseries is the Quonset hut. This is an elongated rectangular floor plan with arched walls and roof running the length of the greenhouse. It looks something like a large, round culvert sliced lengthwise, with the cut sides placed on the ground.
“THERE IS NO SINGLE METHOD FOR WATERING THE PLANTS INSIDE A GREENHOUSE. WHETHER YOU BRING WATER IN BUCKETS OR USE A HOSE IN THE GREENHOUSE IS UP TO YOU.”
To fabricate such a greenhouse, you’ll need flexible poles that can be used as the ribs for the frame. You will most likely need to attach more than one pole together to go from the ground on one side of the hut up high enough for a comfortable standing height and to provide the desired width and then down to the ground on the other side.
This can be done with commercially available materials, but I have observed sturdy greenhouses where this was done with thin bamboo. To create the framework for such a greenhouse, you might have to fasten the lengths of bamboo together to get the desired length. Remember, you want a greenhouse that allows you to walk in and stand upright, so before you start, work out the length required for each of the ribs making the arch, including the length that will be put into the ground.
To make sure the framework of a do-it-yourself Quonset hut-style greenhouse is secure, you will also need to secure horizontal cross pieces to the ribs that will run the length of the hut. Once the frame is secure to your satisfaction, you can cover it all with plastic, add your platforms and your door and get to work.
A greenhouse allows you to continue growing food and other plants in the winter when they can no longer grow outdoors. It’s also a good environment for fostering the growth of young seedlings and grafted plants.
There is no single method for watering the plants inside a greenhouse. Whether you bring water in buckets or use a hose in the greenhouse is up to you. For smaller greenhouses, it could make sense to capture rainwater that comes off the roof, providing convenient access to that resource. It is not uncommon to see larger, more-permanent greenhouses with internal plumbing because of the greater volume of water required.
I have been in one greenhouse that had an overhead sprinkler system. Although it created an environment that replicated rain, I concluded it was more wasteful of water and did not get the water primarily to the plants that needed it. It was a great attraction, but it was more work and cost than are needed by most greenhouses.
The Quonset hut-style greenhouses at family-owned Nuccio’s Nurseries (Altadena, Calif.) are good examples of low-cost, do-it-yourself greenhouses. This farm, established in 1935, specializes in camellias and azaleas for home gardeners and landscapers. It also does grafting and seed-growing and has developed many unique varieties over the years.
Tom Nuccio, one of the owners, explained that his father and uncle built the five greenhouses on their mountain property in the mid-1950s. Each greenhouse was begun with metal tubing that was bent into a large arch for the shape of the structure. There was one arch about every 4 or 5 feet. These arches were then secured by horizontal wooden strips that were fastened to the arches, giving the basic framework horizontal structural stability.
Most of the Quonset hut greenhouses were first covered with nursery cloth, which provides limited shade by diffusing the sunlight. This prevents young plants from getting sunburned. Plastic sheeting is then draped over the greenhouse, sometimes entirely and sometimes partially, depending on the plants to be grown there. The plastic is secured with straps so the wind doesn’t blow it away.
Because it can get very warm inside these greenhouses, they were designed so that some of the plastic can be removed to reduce the amount of heat that is trapped inside. Nuccio said that some of the greenhouses have gotten as hot as 105 degrees Fahrenheit —too hot — in the summer. The ends of the greenhouses are sometimes left open, but mostly they are framed over and doors are installed. The door can then be opened or closed, depending on the heat. The nursery doesn’t use any fans to reduce excess heat, nor does it typically bother with thermometers.
Nuccio’s greenhouses are primarily intended to create a humid environment to make it more conducive to grow young plants and protect some plants throughout the winter.
At least one of the Nuccio greenhouses is covered with a layer of chicken wire. It was installed one year to protect the greenhouse from the weight of snow, although it’s not common in that area.
The Nuccio greenhouses were built for a commercial enterprise, but they were still built by hand using suitable materials that were available. These greenhouses have lasted for more than six decades, with only occasional upkeep.
Whether you are just starting out or looking for replacement parts to get an existing greenhouse back into shape, there are plenty of suppliers that can sell you anything from sheeting and polycarbonate panels to a top-of-the-line commercial greenhouse suitable for a serious farming operation.
Growers Solution sells greenhouse covers of various materials, as well as complete greenhouse kits. The prices and sizes vary, but this company has a variety likely to include an option for any level of interest and experience.
Peaceful Valley Farm Supply sells a few kits in various price ranges. For example, you can purchase a 6×10-foot greenhouse with framing and cover for $768, or you can get an 8×16-foot greenhouse with redwood framing for $4,218. This company also has a selection of sheeting and panels to suit many types of greenhouse construction.