|Greenhouses: How to Choose & Where to Buy|
• Greenhouse benefits, drawbacks
• Types of greenhouses
• How to choose which greenhouse to buy
• What greenhouse materials to look for
• Greenhouse accessories
• Assembling a greenhouse
• Tips for first-time greenhouse buyers
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|Greenhouses enable gardeners to ensure productive crops regardless of the weather or growing region.|
|Greenhouse gardening used to be the sole domain of commercial plant producers who require a protected, controlled environment to grow flowers and food crops indoors off-season, or to raise starter plants and shrubs for resale. More recently, due to modern materials and new construction techniques, many new types of greenhouses have become available for sale to anyone interested in gardening. In fact, it's become common today to see small greenhouses in residential backyards.
Homeowners and gardeners who are thinking of buying a greenhouse have two decisions to make:
Do we need a greenhouse? If so, with so many choices on the market, how to choose which greenhouse to buy?
|Do you need a greenhouse?
Gardening in greenhouses has become increasingly popular due to three trends which affect gardeners everywhere:
1. New materials have made greenhouses less expensive and longer lasting
Greenhouses have become much more affordable recently because of new materials which lower the cost and increase the lifespan of modern greenhouses. Manufacturers have responded to these developments by producing a wide variety of new greenhouses of all sizes and styles, and in a wide range of cost.
2. Food security is enhanced with a home greenhouse
To many people, faith in food security is shaken by each new report of outbreaks of sickness from various produce providers. Also, the cost of food, especially produce, has risen considerably due in part to transport costs, and it's getting to the point where it may be healthier, less expensive, and more secure to provide your own food for the family.
3. Climate change brings uncertainty to outdoor growing conditions
The frequency and strength of seasonal storms is increasing, as predicted by climate scientists. Gardeners across the world are losing crops and topsoil to unusually strong weather accompanied by heavy rains which flood ground crops and wash away topsoil where most soil nutrients reside. In our garden, we recently had a major 'November' storm arrive two months early, breaking many of our tomato plants, knocking over the fall brassicas (cauliflower, kale, broccoli, brussel sprouts and cabbage), soaking the winter squash which should have been curing in the early autumn sun, and throwing our fall fruit harvest off schedule. As gardeners, we now have the added risk of unexpected weather events. Growing our principal crops in a greenhouse, or starting crops early in a small greenhouse, is our best assurance of a fruitful harvest in uncertain times.
Benefits and drawbacks of greenhouses for gardening
Besides the trends mentioned above, there are many practical benefits, and some drawbacks, in using a garden greenhouse to start or grow crops under shelter.
|• Extends the growing season - A greenhouse lets you start seedlings earlier in the season so they're well developed when the weather outside becomes warm enough to set them out. Greenhouses also enable gardeners to grow crops later in the season and further extend the harvest.
• Provides fresh vegetables all year - In warmer climate zones, or with insulated or heated models for colder regions, a greenhouse enables you to grow cool and warm weather crops all year.
• Protects germinating seeds and seedling starters from harsh weather - Greenhouses protect fragile new sprouts and young seedlings from weather events like late frosts, cool spring weather, heavy rains, wind and hail.
• Protects seedlings from soil and air-born insect pests - Hidden pests in the subsoil such as wireworm, slugs and pill bugs may emerge at night and damage fragile new sprouts and young seedlings. Air-born pests such as cabbage moths can destroy sprouts of Brassicas such as broccoli, cauliflower, cabbage, kale and brussel sprouts.
• Protects sprouts and seedlings from birds - Bird activity increases during spring, and many bird species will dig and scratch into the upper layer of soil in search of bugs and worms. This disturbs germinating seeds. Emerging sprouts are also susceptible to bird predation.
• Plants can be grown in containers or directly in the ground - Greenhouses are commonly used for growing starters in pots for transplanting outdoors, or for growing plants to maturity in containers or deep shelves. Plants can also be grown directly in the ground in greenhouses, which enables crops susceptible to airborne diseases, like tomatoes, to grow larger.
• Saves money on plants - The controlled environment of a greenhouse results in a high rate of success with seed germination. This lets you grow as many plants as you like, without having to pay for ‘starters’ at your nursery center.
There are some drawbacks to gardening in greenhouses which can be mitigated by choosing the right greenhouse and greenhouse accessories for your growing region.
• Watering needs to be monitored - Since seasonal rains will not reach your greenhouse plants, you need to pay attention to soil moisture levels. Plants grown in containers have the benefit of being well-drained, but have the liability of drying out faster than plants grown outdoors in the ground. There are automatic watering systems available as greenhouse accessories which can address watering needs.
• Plants can overheat and lose vigor - An unvented greenhouse can get too hot in summer and cause plants to wilt or die. Most greenhouses provide ventilation, but manual vents may be left closed at times. Automatic vents are a great solution, and available as accessories with most greenhouse designs.
What are the different types of greenhouses available on the market?
Choosing which greenhouse is right for you can be a daunting task, since buying a greenhouse is an investment which requires some research. To help narrow down the choices among the many greenhouses for sale today, you can choose from among these general types of greenhouses based on your garden needs.
|Cold frames – These 'mini-greenhouses' are designed to be set directly on a garden bed for direct seed germination and for hardening off transplants. Cold frames are primarily used in early spring to get seedlings to sprout and take root where they would otherwise perish due to frost and cold spring rains. Cold frames can be moved to different beds to follow the spring planting schedule. Visit Eartheasy's online store to see a wide variety of Cold Frames.
Starter greenhouses – These small and mid-size greenhouses are very popular for propagating seeds and starter plants which will be transplanted outdoors to garden beds. The starter, or hobby, greenhouse also doubles as a potting shed, where garden supplies can be kept under cover, transplants can be repotted, and harvested crops can be brought in to cure and be processed for winter storage. These greenhouses often have clear or semi-diffused coverings, since the direct light favors seed propagation. Click here to see our selection of Starter Greenhouses.
Grower greenhouses – These are larger greenhouses, often with adjustable shelving, for growing crops full-term indoors under shelter. Diffused or semi-diffused coverings are common for these larger greenhouses. These are all-purpose greenhouses, good for propagating seeds, great for indoor growing of crops, and spacious enough for curing harvested crops and preparing them for storage. Click here to see our Grower Greenhouses.
Another way of differentiating the types of greenhouse is by temperature level. Whichever type of greenhouse you purchase, you have the choice of three basic ways of approaching greenhouse gardening – hot, warm and cool.
Hot house greenhouse – or 'hot house', has a stable temperature in the range of 65 – 70 degrees, or higher. This temperature range is used to grow exotic and tropical plants. Heaters and grow lights are usually needed to maintain this level of heat.
Warm greenhouse – has a stable temperature in the range of 50 – 55 degrees. In this temperature range, you can grow plants which you would grow in your outdoor flower or vegetable garden. You may need to use grow lights or heat lights to meet the heating needs during the winter night months.
Cool greenhouse – or 'frost-free' greenhouse, has a stable temperature in the range of 40 – 45 degrees. This is an ideal temperature range for a 'nursery' greenhouse, where you will be germinating seeds and raising your own starter plants and vegetables for the summer months. You generally don't use grow lights or heat lights in this environment.
What factors should be considered when looking to buy a greenhouse?
|R-Value - the measurement of 'insulating ability' of the material. Higher R-Value refers to higher insulation value.
U-Value - the measurement of 'heat loss' through the material. The lower the U-Value the less heat is escaping.
|Beyond the insulation value of the covering material, greenhouse suppliers offer a variety of insulating schemes, depending on the needs of your growing environment. Foundations, walls and roofs can be insulated. For the do-it-yourself gardener, an inexpensive method is to use bubble wrap. Some garden centers provide UV-stabilized polyethylene bubble wrap for this purpose. We recommend that you choose wrap with large bubbles as this has better insulating properties and lets in more light.
Panel clarity: diffused (opaque) vs. clear
Some greenhouses are designed with clear coverings or panels, while other models have translucent or opaque coverings. And some greenhouse models have semi-diffused covers which provide some of the benefits of both clear and diffused models.
Clear panels deliver direct light while opaque panels provide diffused light. If you want to buy a greenhouse to germinate seeds and grow starters which will be transplanted outdoors, then a clear covering has the advantage of bringing full, direct light to the starter trays. This warms the soil and encourages germinating seeds to sprout and develop into a vigorous starter plants for transplanting. Examples of clear-covered greenhouses are the Nature, Clear View and Snap and Grow greenhouse models.
While it may seem counterintuitive, diffused light provides superior light for growing plants. Diffused light may appear to be less bright than direct light, but the light that generally produces the most efficient photosynthesis is not visible to the human eye. Diffused light reaches your plants from many angles, so plants do not get ‘leggy’ as they would when competing with each other to grow towards available light. With diffused lighting plants develop a more balanced, compact structure. The Solexx greenhouses all have diffused covers.
What materials should prospective greenhouse buyers look for, or avoid?
Materials used for the glazing, or outer covering, of greenhouses have come a long way since the old-fashioned glass greenhouses. Different types of plastic, and tempered glass, are used today for greenhouse applications. These come in the form of sheets or panels, and range in clarity from clear to diffused.
Glass and clear plastic function in basically the same way, by allowing light to pass through while trapping heat inside. Plastics are generally lighter weight and less expensive, but not as durable to weather and age. Glass greenhouses cost more to build initially, but hold up better over time.
When choosing which greenhouse to buy, you’ll need to consider whether you want it for a ‘season extender’ or if you intend to grow vegetables indoors through the winter. If your region has cold winters, i.e. if it freezes or snows, a well-insulated covering is needed.
~ Tempered glass – Tempered glass panes are very strong and impact-resistant, and will withstand expansion and contraction during seasonal temperature changes. Single-pane thickness of 3mm is adequate for greenhouses, but 4mm thickness is stronger and provides additional insulation value. The edges must be protected during installation, as they will shatter the pane if hit with a hard object. Tempered glass is more expensive than polycarbonate panels, but it is more durable and scratch-resistant. Tempered glass is clear, and provides no diffusion.
Insulation values of polycarbonate greenhouse glazing
The image to the left shows the construction and relative thickness of available multi-panel polycarbonate glazing used for greenhouse cover panels.
Note that the vertical separators have three functions – they add structural strength to the panel, increase insulation value by providing an air space, and serve to break up, or diffuse, the light passing through the panels.
A greenhouse frame provides structural integrity and serves to anchor the greenhouse covering. Greenhouse frames are available in a variety of materials.
|~ Aluminum – Aluminum provides a strong, lightweight frame that will not rust. It is the most widely used material for greenhouse frames, and it has a very long life span. Aluminum frames commonly have extruded channels which provide a perfect fit for inserted covering panels. Aluminum is not an insulative material, so there will be some heat loss through the framing. Powder-coated aluminum retains a smooth outer finish as well as providing different colors.
~ Steel – Galvanized steel frames, usually tubular, are extremely strong, long lasting and low cost. Because of steel's inherent strength, minimal structure is required for framing, which results in additional light getting through to the plants. Polyethylene film is often used for covering steel framing because other covering materials require fastening systems which do not lend themselves to steel frameworks. Steel frames are heavy, which helps the greenhouse remain stable in windy conditions, but the weight makes transporting and assembling the greenhouse more difficult. Steel is usually used for large commercial greenhouses.
~ Plastic resin – Plastic frames have become popular because they are attractive, less expensive than aluminum and do not conduct heat out of the greenhouse as much as steel or aluminum. Plastic frames lack the strength of metal frames, so they are used primarily for smaller greenhouses which have shorter dimensions. Plastic frames are often designed to be used with polycarbonate panels.
~ Wood – Wood greenhouse frames are often used in do-it-yourself greenhouse building projects. Wood can provide an aesthetically pleasing appearance and sufficient strength and durability. However, wood is susceptible to rot, so the construction should ensure that the wood does not contact the ground or any moisture holding surfaces.
What are a few important greenhouse accessories to consider?
When you purchase a greenhouse, take into consideration what accessories are included in the purchase price. Although most greenhouses are sold 'ready-to-use', there may be some options you will want to add to help ensure your success with greenhouse gardening. You can also buy a simple starter greenhouse and add these accessories as needed and as your budget allows.
|Automatic louvers – Greenhouses usually come with opening vents which are essential to controlling interior heat. Solar-powered automatic louvers are available which enable the gardener to have a life outside the garden. These louvers will open and shut according to preset heating levels, and are a gardener’s best assurance that plants won’t be lost to overheating.
Automatic irrigation systems – We have lost entire sets of seedlings because we forgot to water them in time. Drip-irrigation systems, drip tape (flat hose with tiny holes), and soaker hoses can be set on inexpensive battery-operated timers which you can set onto your faucet bib.
Greenhouse shade cloth – Especially useful for clear or semi-diffused greenhouses, shade cloth can be draped over the greenhouse roof to lower the inside temperature. Look for UV-stabilized knitted shade cloths with brass grommets, available in various densities. A simpler, very inexpensive method is to use split-bamboo blinds, which you can often find in shops. Shade cloths should be secured at the top of the structure and installed so that it is easy to draw them back during morning and evening hours as needed.
Hand-watering wands – It’s easy to flatten young sprouts with too strong a water spray. Watering wands with adjustable nozzles are designed to let you reach to the back of seedling trays and different shelf heights without having to bend over. Fine ‘misting’ settings deliver water to germinating trays and seedlings without disturbing the soil or the tender sprouts.
Potting bench – When growing your own starts from seed, you’ll need a firm surface to work on, a container to hold the potting soil and an easy way to sweep the soil spilled during potting back into the potting soil bag. Potting benches are designed with all this in mind, helping you keep the potting accessories in one place and the overall appearance of the greenhouse more organized.
Galvanized steel braces - are available that will allow you reinforce the base of your greenhouse. This is useful in areas where strong winds may impact your greenhouse and potentially shift it from its foundation.
Custom shelving – Different styles of greenhouse shelving are available which enable you to customise the interior layout of your greenhouse. Aluminum shelves with interchange heights are popular. Others can be re-arranged into different geometrical shapes for attractive displays and maximizing space usage. They come in a variety of colors, with plastic liners, wheels and all sorts of different options.
Heaters – Many different types of greenhouse heaters are available. Grow lights generate considerable heat for the plant, although they do not warm the soil. Some lamps or ‘toaster-coil’ types will spot heat a corner. Others, such as track systems, can be attached to the roof and heat the entire greenhouse in the winter
What is involved in assembling a greenhouse?
Most greenhouses are sold as greenhouse kits, and are shipped flat in multiple boxes. The customer is expected to do the assembly. Before purchase, be sure to check the assembly requirements. Which greenhouse you buy will be partly determined by the assembly requirements. Some greenhouse kits only take 4 – 5 hours to assemble, but it is safe to assume that assembly will be a weekend job for two people. No special tools are needed, but you will need basic handyman skills.
Tips for the first-time greenhouse purchaser
~ Read the Warranty. The warranty may vary by manufacturer. When deciding which greenhouse to buy, don't forget to check out the warranty. How long are materials guaranteed to last? What is the duration of the warranty? What parts are covered? Your home insurance policy can also be amended to cover your greenhouse from weather events, such as strong winds and hail, which may not be covered by the greenhouse warranty.
|• Raised Garden Beds
• Natural Pest Control
• Natural Slug Control
• Gardening with Children
• Portable Garden Cloche
For Greenhouses and gardening products, visit our online store.