Greenhouse Buying Guide
For the avid gardener, the addition of a greenhouse will create a whole new dimension to the excitement and pleasure of the gardening experience.
While your outdoor garden is susceptible to weather and seasonal changes, a greenhouse is the ultimate controllable microclimate. In your greenhouse, you can grow superb tomatoes, strawberries and other fruits and vegetables that are not appropriate for outdoor planting in your region during colder months. Greenhouses are an ideal place to grow and force bulbs, and you can also start thinking about creating an amazing collection of tropical plants, such as orchids.
Greenhouses allow you to enjoy gardening and working with plants while the outside world remains cold and inhospitable. Moreover, your greenhouse can help you get a head start on the gardening season by allowing you to grow starter plants that will be ready for transplanting when spring arrives.
Greenhouses come in a myriad of sizes and shapes, with certain styles being appropriate for certain kinds of gardening. They range from cold frames and small portables to large commercial buildings. Before you venture out to buy a greenhouse, you should learn as much as possible about the different styles available and which greenhouse is appropriate for the kind of gardening you’d like to do. come in a myriad of sizes and shapes, with certain styles being appropriate for certain kinds of gardening. They range from cold frames and small portables to large commercial buildings. Before you venture out to buy a greenhouse, you should learn as much as possible about the different styles available and which greenhouse is appropriate for the kind of gardening you’d like to do.
This guide is designed to help you learn about greenhouse gardening principles and the various models available so that you can get the most out of your greenhouse gardening experience.
Greenhouse Basics
A greenhouse is basically an enclosed structure that has transparent or translucent walls that allow sunlight to warm the space and create a microclimate. Greenhouses also allow you to control the amount of air and water your plants receive, as well as the temperature and humidity.
Greenhouses are usually a framework of wood, metal, plastic or PVC pipes with panes of glass or polycarbonate sheeting on all sides. Some greenhouses are portable and use polyethylene sheeting. Like garden arbors, they are generally easy to assemble and to take apart for summer storage. Greenhouse kits are available in varying sizes and styles that can be erected by do-it-yourself homeowners. More elaborate greenhouses can be built for you by a contractor.
While greenhouses are designed to capture the sun, they are also designed to control the level of shade with shade cloth or shelving units. You can have a small area for shade loving plants, and control the levels of filtered sunlight with different layers of shade cloth.
The variability and flexibility of the greenhouse allows you to grow just about any kind of plant you want, no matter the climate of where you live or what time of year you wish to garden!
We’ll talk more about how greenhouses work after we discuss thebasic types and their uses and the principles of setting up your greenhouse.
Your Ideal Greenhouse Environment
Deciding which greenhouse is right for you begins with brainstorming ideas for how you want to use your new greenhouse. For example, if you want to start a collection of orchids and you live in a colder part of the country, you will need to consider buying a substantial greenhouse with sufficient insulation to keep your plants under appropriate growing conditions year round. In this case, your greenhouse may have triple-pane glass or polycarbonate panels which will provide the proper insulation. It may also have a frame that is insulated, as well as insulation around the foundation. Sound complicated? Not to worry. Keep reading and you’ll quickly learn that selecting a greenhouse is easier than you imagined.
While you’re researching greenhouses, it is a good idea to take notes and make sketches of your property. Think about issues of space and the budget you have to work with. Rest assured that you will be able to find a greenhouse that fits your needs.
One fundamental idea in greenhouse design is how the interior microclimate is regulated. The more delicate your plants and the more varied your needs, the more you should consider insulation and more elaborate systems of irrigation and climate control. Less expensive greenhouse structures, such as cold frames and hobby homeowner kits (Clean Air Gardening greenhouses) can work very well for the casual greenhouse gardener. Simple designs may involve just a frame and polycarbonate panels that create a warmer environment than you have in your garden. These are ideal for extending the growing season, storing delicate plants in the early spring and late fall, forcing bulbs, etc.
As you get into more advanced greenhouse gardening, you may buy a greenhouse that has electricity and the possibility for regular irrigation. For example, if you plan on growing a collection of expensive orchids, you may consider a control system with sensors that will automatically open and close vents, adjust the temperature, and turn on and off a mist system. These systems can open and close a roof cover, and even send an alarm to the house (or your cell phone) if there is a problem. Your greenhouse may require lights and heaters, as well as fans. However, very few homeowners are actually going to need a system this costly and elaborate.
Of course, in the case of the more basic greenhouse, you will need to take more responsibility for controlling the climate inside the greenhouse. Believe it or not, this can actually be the most enjoyable part of greenhouse gardening. You can check the temperature, humidity, soil acidity, soil temperature and tweak things as needed. As you watch the results of your nurturing, you will realize that your greenhouse is a unique and malleable gardening space that you control.
Basic Greenhouse Types and Uses
Freestanding or Attached Greenhouses?
The most basic consideration for your greenhouse is whether you want a greenhouse that is attached or freestanding.
An attached greenhouse simply means that it is connected directly to your home. These include lean-to greenhouses.You can even consider building on a sunroom that will heat up like a greenhouse but can be used for relaxing during winter months. An attached greenhouse can be convenient in that you can make use of the infrastructure of your home to provide electricity and heat. Being close to your house also means that the greenhouse will naturally receive some heat radiating off your home. You just have to make sure that you have a decent south-facing location to take advantage of the winter sunlight. You should investigate also the building restrictions in your community in case you need a permit to construct your greenhouse.
A free standing greenhouse is a completely independent structure from your home. Depending on the size of your yard, they offer the advantage of being as big as you can build them. They also have the advantage of receiving more sunlight than attached greenhouses. However, depending on the kind of gardening you what to do, they can require a greater investment in heating and electricity.
Two Basic Greenhouse Models: Cold Frames and Grow Racks
Coldframes provide the smallest and simplest greenhouse environment and are usually made from polycarbonate panels. They are ideal if you don’t have much space. They can be used to give you an early start with tender flowers, herbs, and vegetables. If you sprout seeds indoors, coldframes can also be used to harden the tender plants before they are planted outside.
Coldframes can also be used during winter to protect sensitive plants. When coldframes are not in use, they make great storage containers for your seeds, bulbs, and other gardening supplies. They are generally not intended for growing exotic or delicate plants year round.
Grow Racks are the next size up and can be an attractive addition to your patio or deck. They usually come with a vinyl cover and zippers or Velcro. The zippers or Velcro allow you to adjust the vinyl cover so that you can modify the air flow, temperature, and humidity. Special heat pads can be used under planter boxes to maintain the ideal soil temperature for your plants.
Grow racks can even be an elegant indoor addition for sensitive tropical plants, or for sprouting seeds.
Portable Greenhouses
Portable greenhouses come in a variety of sizes that can range from 6 ft. x 10 ft. to 50 ft. x 100 ft. Some of them use metal frames and cover the frames with heavy-duty polyethylene sheeting.
Of course, the very large portables aren’t really that “portable.” However, the smaller portable greenhouses are economical and convenient for homeowners. They often come in greenhouse kits that are easy to assemble and disassemble. They can extend your growing season and enhance the joy of gardening.
Although they are easy to take apart and store during the summer, you may decide that you want to use your portable greenhouse all year round. Be sure that you’ve purchased a portable greenhouse that will stand up to your local weather conditions, especially if you live in an area with extreme temperatures and lots of wind. You can always take your greenhouse down and store it during the most inhospitable months of the year so that it will last longer.
Permanent Greenhouses
Many permanent greenhouses also come in greenhouse kits that do-it-yourself homeowners can put together. They can be more expensive than other kinds of greenhouses, but they are sturdier and more durable. They can take a little longer to put together and may take an extra person or two to get the job done. However, if you are an avid gardener who wants a sturdy greenhouse that provides a range of gardening options, a permanent greenhouse is for you.
Permanent greenhouses come in many sizes and shapes. A large variety of kits are available for both large and small permanent greenhouses. If you want a more substantial greenhouse, you may want to hire a contractor to put it together or build it from scratch.
It is important for you to decide how you will use your permanent greenhouse before you make a purchase. That will ensure that you pick the size and options that are ideal for you. It may be worth while for you to pick the biggest one you can afford because you may enjoy it so much that you run out of space!
Permanent Greenhouse Styles
Except for the Lean-to style, permanent greenhouses can also be referred to as free standing greenhouses. The basic types are described below. As you look at the various styles, remember that you will be happiest if you pick a greenhouse that fits your gardening plans and also looks good in your yard.
Lean-to
Lean-to greenhouses are permanent greenhouses that attach directly to a wall of your home, garage, or other structure. They are usually smaller than other permanent greenhouses. If your lean-to greenhouse is in the right spot, you may be able to provide electricity and plumbing directly through the wall.
Lean-to greenhouses can do as many things as other permanent greenhouses, and are usually more accessible in foul weather.
Classic A-Frame
Classic A-Frame greenhouses have slanted sides. They are strong and can easily handle snow. However, some growing space is lost because of their slanting walls. They are also expensive to heat because of their high ceiling.
Modified A-Frame
Modified A-Frame greenhouses are built with Gable roofs, which are usually not as steep as classical A-Frames. Their shape is similar to what most of us think of as a typical house, except modified A-Frame greenhouses don’t have eaves. Their straight walls use space efficiently. Since the roof slope is not as steep as a classic A-frame, the heating bill can be a bit less.
Quonset Hut
Quonset hut greenhouses, sometimes referred to as “hoop style,” are inexpensive and easy to heat. However, their round walls are not necessarily the best use of space. Quonset Huts usually use polyethylene sheeting or sheets of polycarbonate because of their round structure.
Gothic Arch
Gothic Arch greenhouses are similar to the Quonset style, except that the sides are usually straighter and the curved roof is pointed on top. They often have a beautiful shape and are one of the more aesthetically pleasing greenhouse styles.
Barn-Style
Barn-Style greenhouses have perpendicular walls like the modified A-Frame and do not have eaves. They have a Gambrel roof, which creates the barn-like design. Their straight walls make good use of space.
Greenhouse Styles based on temperature
In addition to their design, greenhouses can often be described by the temperature you wish to maintain. Greenhouses can be referred to as cool (“frost-free”), warm, and hot greenhouses (also known as a hothouse), depending on the temperature they maintain and their basic design. While a number of greenhouse designs can serve the purpose of a cool, warm, or hot greenhouse, they may need special equipment to help maintain their temperature.
A cool greenhouse is where temperatures stay around forty degrees F. You can use these greenhouses for seedlings or for storing other plants that won’t need a constant high temperature. For a cool greenhouse, you generally just need the structure and a decent amount of insulation.
A warm greenhouse is a greenhouse where temperatures hover around fifty degrees F. This means that most plants you grow outdoors in your region as tender perennials will survive through the winter in this environment. Some kinds of houseplants do well in warm greenhouses as well. Depending on where you live, you may need special equipment such as lamps as winter months reach their lowest temperatures.
A hot greenhouse is typically used to grow tropical plants and maintains a temperature of 70 degrees or warmer. Hot greenhouses often need special equipment to maintain their temperature such as grow lamps.
Pit and Solar Greenhouses
The basic idea of a pit greenhouse is that you grow your plants at ground level and dig a walkway underground in order to have access to the plants. You can dig the walkway about 3 feet deep and then line it with plywood or another material. This site has a simple description of a pit greenhouse construction and a few nice photographs.
Solar greenhouses are designed to collect and store solar energy to keep your plants warm at night and when the weather is cloudy and colder. They can have a similar design to regular greenhouses and can be either freestanding or attached structures. You can also combine a solar and a pit greenhouse. Free-standing solar greenhouses are more appropriate for growing plants in large quantities and attached structures are appropriate for home use. As with other solar structures, solar greenhouses can either be passive or active.
Passive solar greenhouses are a good choice for the home gardener as they are inexpensive to operate. You can also combine solar energy with other forms of heating to maintain your greenhouse warm during the coldest months. Active solar technology requires more investment and uses solar energy to heat water or air cells where the energy is stored. Photovoltaic heating is also an option can be very expensive.
Setting Up Your Greenhouse
Now that you know the basics of greenhouses and what you can accomplish with one, here are a few other suggestions to get you thinking about how to set up your greenhouse. These factors may also influence what kind of greenhouse you buy.
• Make sure that you have an area of your yard where your greenhouse will get enough sunlight. You may need to make a few changes in your landscaping to let the light in.
• Provide easy access to your greenhouse. You may perhaps want big enough doors to get a wheelbarrow or cart through. You will also need easy access when the weather gets nasty.
• Make sure that you have an area with good drainage. Pooling water in your greenhouse may increase humidity and also make for a less enjoyable gardening experience.
• Unless you are using a coldframe, grow rack, or portable, you will need a squared and level foundation. See Setting Up Your Greenhouse for more information.
• For more complicated greenhouse gardening, you’ll need to think about installing electricity for fans, lights, and other necessities.
• Place your greenhouse where you’ll have a source of water close at hand. If you don’t have a hose or other water source where you want to set up your greenhouse, make sure to install a new one.
• Try and pick the biggest greenhouse you can afford for your space. This will allow you more options for gardening in the future.
• Double or triple walled panels are expensive, but will provide important insulation for growing certain kinds of plants. Make the investment if you can and you won’t regret it.
Need more information? You’re ready to move on to our page on basic greenhouse types and their uses. Also, check out our links pages for some great resources on greenhouses. Your local library and book stores can also help out for books about greenhouses.
Location, location, location!
When you are setting up your greenhouse, you will need to maximize the sun exposure to take advantage of the solar energy. Most professional gardeners say that six to seven hours of direct sunlight during the winter months is ideal.
Before you install your greenhouse, observe your yard from the early morning to the late afternoon and note the amount of sunlight each area receives. You may need to make some changes in your landscaping in order to maximize sunlight. Consider pruning a tree or two to let more sunlight reach your greenhouse. In the case that you live in the Northern most parts of the country where the days are shortest, you can think about buying grow lights as an option to compensate for the short days.
Also, remember that the closer your greenhouse is to your home, the better. Greenhouses can receive a little extra heat as it is radiated off your house during the winter. Also, the closer your greenhouse is to your home, the easier access you’ll have during the coldest and most inhospitable winter months. Keep your greenhouse away from landscape features that may damage the structure. These include rapidly growing vines or older trees that may have old branches that could fall and damage your greenhouse.
Building A Foundation for a Greenhouse
While the structure itself is the fundamental part of your new greenhouse, it’s important not to forget the surface where you’re going to place it. Depending on the style of greenhouse you choose, you will probably need to set up some kind of foundation. The benefits of a foundation include an additional surface to soak up the sunlight and release the absorbed heat at night. Many hobby and portable greenhouses work fine without a foundation if you’re interested in only casual greenhouse gardening.
A foundation can be fairly simple, or it can be professionally built. If you are a serious gardener who wants to set up a large greenhouse, it’s a good idea to hire a contractor to set up your foundation. A basic poured concrete foundation may work for you and are easy to make yourself. A dirt floor with a little gravel mulch also works fine for a small portable hobby greenhouse.
You can consider installing several types of foundations for your greenhouse, including concrete, brick, and wood. Concrete is durable but you must also think about drainage issues. A brick foundation can be built to have adequate spacing between the bricks that will allow for some drainage. Wood is a good option as an inexpensive foundation but you will need to keep treating the wood so that it holds up to the moisture and water used in gardening.
You can consider installing several types of foundations for your greenhouse, including concrete, brick, and wood. Concrete is durable but you must also think about drainage issues. A brick foundation can be built to have adequate spacing between the bricks that will allow for some drainage. Wood is a good option as an inexpensive foundation but you will need to keep treating the wood so that it holds up to the moisture and water used in gardening.
Proper Ventilation for your Greenhouse
Once your greenhouse is set up, one of the most important things to consider is ventilating your greenhouse space. Greenhouses that are not properly ventilated may experience extreme humidity and heat, and cause some of your more delicate plants to suffer from stress. You will also need to keep fresh air circulating into the greenhouse so that there is a balance of oxygen and carbon dioxide.
Simple kit greenhouses include vents to allow air to circulate. Ventilation in the roof and walls are standard. More complex greenhouses require fans and vents to help circulate the air and control temperature.
You may notice that certain areas of your greenhouse concentrate the hot air more intensely than other areas. Proper ventilation minimizes this problem by allowing the hottest areas to cool off and balance out with the rest of the greenhouse. This will help your plants avoid the shock of extreme heat.
In addition to letting fresh air in, in some cases it is important to occasionally open the vents during the cooler months to allow your plants to gradually become used to the cold. If you’ve kept your vents closed and temperatures hot, imagine if the temperature suddenly drops and you open the door to your greenhouse. Your plants will not appreciate the shock.
Automatic systems are available if you have a busy schedule and want a more carefree greenhouse gardening experience. They can be expensive but are a good option for the serious gardener. During the coldest months, the temperatures will not reach the extremes that they do in the summer. You will probably need to open the vents infrequently during this time.
Greenhouse Watering Systems
How you provide water for your plants is an important part of greenhouse gardening. You should try and have a source of water as close as possible to your greenhouse. You may need to set up a separate hose if you don’t have one close by to where you want to set up your greenhouse.
The most basic hobby greenhouse gardening will only require a hose. On the other hand, if you plan on getting into serious greenhouse gardening, you should look into other types of water systems such as overhead watering systems and misting systems. These types of systems can be automated to control how much water your plants receive. Misting systems are ideal for tropical plants and epiphytes.
Capillary Matting is another option for watering your greenhouse, especially if you have a large number of plants. The capillary mats provide water through the bottom of the pots or trays if you’re growing a large number of seedlings. Capillary mats work in conjunction with a reservoir that you can fill up by hand or set up for automated watering.
Drip irrigating systems are also a good choice and great for water conservation as they apply a small controlled amount of water directly to each plant.
Greenhouses are ideal for gardening with hydroponics. This is a unique gardening method that avoids the use of soil altogether. Check out this site for more information on hydroponics.
Greenhouse Maintenance Tips
Now that you’ve made your investment, you need to learn how to care for your greenhouse so that will have a long life. This requires performing a few basic tasks you can do every day, and more intensive chores that you maybe need to do once or twice a year. Regular care of your greenhouse is an essential part of successful greenhouse gardening and will also mean healthier, more robust plants.
As mentioned before, monitoring the temperature of your greenhouse and opening vents is an important daily task. As you open and close the vents make sure they seal correctly and that there are no damage in the material or rips in the fabric. Monitoring for pests is also important. Most greenhouse kits have vents with a screen over them so that insects won’t enter your greenhouse. Make sure that the fabric is intact and that no holes are present that will allow insects in.
Checking the frame of your greenhouse is important, especially if you have a wood frame. You may need to regularly waterproof the wood. Check for rotten boards and also look out for termites that may be damaging the structure of your building. If you have metal or a PVC frame, make sure there is no visible warping of the frame. You may have a cover that is too heavy for your frame.
During the cold months and windy days, your greenhouse may suffer damage. It is a good idea to monitor on a monthly basis to make sure the greenhouse panels are complete and in good shape. You may need to tighten your panels if your greenhouse has experience high levels of wind. If you have a plastic cover, you made need to replace it as often as every year due to tearing.
At least two or three times a year, you should clean the panels of your greenhouse, both inside and out. Use a biodegradable soap such as Castille soap and rinse with water. It is also a good idea to periodically remove all your plants and wash down the shelves and tables. Cleaning your greenhouse regularly will help reduce the formation of bacteria and molds that might affect the health of your plants.
Be aware that some greenhouses are not meant to be left outside all winter in areas with heavy snow fall. These greenhouses, know as season extenders, are really designed to help with starter plants in the spring, and to extend the growing season an extra month or two in the fall. If they are left to be battered by the elements, this can significantly shorten their lifespan.
Of course, it’s important to have a few monitoring tools handy for your plants to make sure they are living under the correct conditions. A high quality garden thermometer is very important for monitoring your greenhouse temperature. Also, this great Electronic Soil Tester for Garden Plants will give you information on soil pH, soil moisture, light intensity, and total combined nitrogen and phosphorus and potash levels.
Energy Conservation Tips for your Greenhouse
Once your greenhouse is set up, you may consider performing some improvements in the future so that you can maximize the energy efficiency of your greenhouse. Some of these additions can be costly, so you can perform a few at a time, or just one.
For added heat efficiency, you can invest in interior plastic liners that are typically around three millimeters thick. External covers are also available depending on the size of your greenhouse.
Of course, making sure your greenhouse is properly sealed is very important in keeping the heat inside your greenhouse. For example, some studies suggest that if you have a glass lapped greenhouse with limited sealing, you can save up to 40% in energy costs by properly sealing all the glass laps as well as the frame.
Another option is to use curtains and screens to insulate your greenhouse. Ohio State University has written an excellent report on using greenhouse curtains and screens for their insulating properties.
Thermal blankets are also a good option to keep your plants warm during the winter without installing expensive heating units. Thermal blankets typically come in ¼” flexible polypropylene foam, a polyethylene foam laminated with 3-mil UV resistant P/E, or a 1/4” closed cell polyethylene foam laminated to white UV treated polyethylene film. Thermal blankets also come in fleece.
Plant heating mats can also be a great resource for heating seedlings and other plants. You can provide heat to only the plants that need them and thus avoid more expensive heating units.
A Note on Greenhouse Materials
What your greenhouse is made of is an important factor in durability, how much heat your structure can retain, and how expensive it may be to keep your greenhouse warm during the coldest months. Here, we’ll discuss the most common materials for frames and covers and their advantages.
When buying your greenhouse, you should think about how easy it will be to expand or add additions on to your greenhouse. With the exception of small portable greenhouses and greenhouse kits, wood is great choice for your greenhouse as it is easy to expand and manipulate. You can easily add boards, attach hooks, etc. Wood will also provide a strong and durable building material. If you use wood for your greenhouse frame, keep in mind that it will need plenty of maintenance to keep the wood strong against the constant moisture and pests that might find the wood a tasty treat.
Metal frames such as galvanized steel are a good choice if you want to worry less about maintenance. Metal is very durable and will hold up well to the weight of your panels or covering material. You may notice however that your greenhouse is a little harder to heat as the metal will hold in the cold.
PVC or plastic frames are a good choice for smaller greenhouses as PVC and plastics are very durable and lightweight materials. PVC pipes can hold up a decent amount of weight, but wood or metal is a better choice if you’re going to build a large greenhouse.
As far as coverings for your greenhouse, glass panels, fiberglass, polythene plastic sheets, and polycarbonate are some of the most common materials you’ll find. Each kind of material works well and has its own strengths and weaknesses. Of course, some coverings are better suited to the hobbyist’s budget.
Fiberglass, polycarbonates, and glass are all good choices for the casual greenhouse gardener. Plastic sheets are common for large commercial greenhouses but are not as durable as other materials and may need frequent replacing. Glass is a very attractive choice, especially if you’re concerned about aesthetics. Glass also allows a large quantity of light to penetrate. When using glass, make sure you have a sturdy greenhouse frame and foundation. Be aware that a glass greenhouse with a metal frame may be more expensive to heat as these materials absorb the cold during the winter. Fiberglass is a good substitute for glass and lets about the same amount of sunlight penetrate. Of course, it is not as attractive as glass and may change color over time.
Polycarbonate is not quite as attractive as glass, but it is more durable. It won’t let as much light in, but an advantage to this is that the sunlight will be slightly less concentrated so your plants won’t receive the intense sunlight that glass greenhouses allow. If you want to reduce heating costs, double or triple polycarbonate sheets work great for keeping the heat in.
Build Your Own Greenhouse
I’m pretty good at gardening, but I’m not much of a DIY kind of person. I can barely swing a hammer. That’s why I wrote a green house buyer’s guide instead of a build your own greenhouse site.
I recognize that most of the world is much better at these kinds of things than I am though, so I found this guide to DIY greenhouse plans.
It goes through all the details about how to choose the right size to build, which type of greenhouse to build, the materials you need to build the greenhouse, and the steps of building it. Check it out!
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