The make, model, manufacturer and site of your hobby greenhouse will determine whether or not you need a base.  The base serves to elevate your greenhouse off the ground, gives you room to put down your choice of flooring and provides a structure for you to attach your nursery.  Most greenhouses come with hardware and are predrilled to fit its proprietary base.  For nurseries that don’t require a base, they can be attached directly to the ground with anchors often provided by the manufacturer.  Your hobby greenhouse must be secure enough to stand the test of time and the elements and protect your investment.  The greenhouse can be secured in your site by digging a 4” to 6” trench consistent with the base dimensions of your structure, placing your greenhouse in the trench and back-filling with the removed dirt, gravel or the flooring of your choice.  For a more permanent structure, forgo using the included base and mount the frame, using the pre-drilled holes, to pressure treated 6”x6” or use railroad ties for a more aesthetic look. (Again, use board footage consistent with the diameter of your greenhouse.)

Attached greenhouses and those covered with glass should have a strong concrete or concrete block foundation that extends below the frost line according to local building codes. A 2- to 3-foot-high sidewall can add considerably to the appearance of a greenhouse. Concrete block, stone, or brick are the most popular materials used, but shingle, clapboard, and asbestos rock have also been used.

Glazing and Paneling

When thinking about what to enclose your greenhouse with, be mindful that there are many different coverings to consider. Glass, Fiberglass panels and Double-Layer Structured panels are all effective glazings, each with its own advantages and disadvantages.

Glass is one of the more traditional greenhouse coverings and also the standard by which all other coverings are judged. Glass is an attractive and formal greenhouse covering. It is also very transparent, allowing your plants open access to direct sunlight. Glass paneling is strong, but can become brittle with age and is subject to shattering. Also, because it is heavier than other materials glass requires a more robust framing support than other covering materials.

Fiberglass reinforced panels are rigid plastic panels made from acrylic or polycarbonate and come in large, corrugated or flat sheets. Fiberglass panels are available in 24 to 57 inch widths and up to 24 foot lengths. They are durable, a better insulator than glass and are lightweight, requiring less structural support. Large panels are flexible enough to be applied to less traditionally shaped greenhouses. Light transmission may be better than glass simply because less structural support is needed, which creates less shadow. Inexpensive materials may be guaranteed for as little as 5 years; more expensive types may be guaranteed for as long as 20 years.

On of the most popular and functional greenhouse coverings, polycarbonate, double-layer structured panels are made of two layers of plastic held apart by ribs spaced 1/2 to 1 inch apart. They are lightweight and can be easily shaped to fit most frames. The double-layer construction increases structural strength and heat retention but decreases light transmission compared to single-layer materials. Most provide a diffused lighting that is beneficial to most plants. Panels are 4 feet wide and up to 39 feet long. Most are UV resistant and carry warranties from 5 to 10 years against yellowing.

Heating and Cooling

Maintaining a constant temperature and protecting against cold snaps and frost is crucial for successful gardening.  In cold, clear or windy weather your nursery may need more heat than is provided by solar radiation; especially at night.  Heat can be supplied using electricity, natural gas or propane, fuel oil, solar energy or kerosene.  Your greenhouse can also be connected to your home heating system. Natural gas or propane is one of the most cost-effective ways of maintaining a constant temperature in your nursery. If natural gas is available in the home, plumbing into the existing line saves considerable cost over a new meter and gas line. If natural gas is not available, check with a local propane gas company for cost and availability. Determine if the company provides a storage tank free or if it can be rented or purchased. Consult the company to determine the tank size appropriate for the greenhouse.

A variety of gas unit heaters are available to heat hobby greenhouses. Unit heaters burn gas in a firebox, the heated air rises through the inside of a thin-walled heat exchanger on the way to the exhaust chimney. A fan draws air in from outside, across the heat exchanger, and out into the greenhouse. Thus, most of the heat is removed from the exhaust before it exits the structure. The exhaust chimney must be sufficiently tall to maintain an upward draft and extend above the greenhouse roof. An 8- to 12-foot chimney is usually sufficient. All open-flame heaters must be vented to the outside and given a fresh air supply for complete combustion. Be sure to provide fresh air circulation to prevent carbon-dioxide build up.

In larger greenhouses, a plastic tube or ducting system may be needed to distribute the heat evenly within the house. The system is made of a perforated polyethylene tube or plastic and wire ducting, suspended overhead in the ridge and extending the length of the greenhouse. A fan connected to the tube blows warm air from the heater into the tube for greenhouse distribution. This system can also be used for circulating internal air when heating or cooling is not required.

A variety of electric heaters can also be used. Those available in department stores and home centers are usually only adequate in the smallest greenhouse for starting seedlings in the spring. Larger units can be purchased, but operating them can be costly.

Heater size for a given greenhouse and geographic location depends on the surface area of the greenhouse and the temperature difference between the inside and outside of the greenhouse. To determine the size heating system you need, calculate the total surface area of the greenhouse covering. Then determine the difference between the minimum expected outside temperature during winter in your area and the maximum night temperature you wish to maintain. The answer will be in BTUs per hour. Most heaters are rated in this unit. Many greenhouse supply or construction companies can help you determine the proper size heater for your situation.

Shades and Light Diffusion

Sunlight is a key component for plant growth. However, natural sunlight is not the best light for plants. In fact, direct light may even damage plants. The same harsh rays that cause sunburns in people can also singe plant’s foliage. Studies show that diffused light is the best light for growing. Growth rates increase 20 to 30 percent under diffused light when compared to plants grown under more direct light. Diffused light reaches your plants from all angles, allowing light to contact leaves that would not normally get much light. Plants are consequently able to photosynthesize more and produce more food to promote healthy, robust growth.

Diffused light also produces fewer shade spots in your greenhouse, which means that plants don’t have to strain to reach towards available light. As a result, the plants develop bushy, compact growth opposed to unattractive, leggy growth. Some greenhouse coverings may diffuse light to some extent, but still transmit too much direct light.  This additional light may ultimately cause more harm than good because too much light causes plants to waste energy through transpiration. Excessive heat, also a consequence of more direct light, can stress plants and reduce photosynthesis rates.

Ventilation is crucial for a productive green house and healthy vegetation.  The purpose of ventilation is to exchange carbon dioxide and oxygen, to remove hot air or cool the nursery and to lower relative humidity. Hobby greenhouses can be vented by natural flow-through ventilation or by forced-air ventilation.

Flow-through ventilation relies on side and top vents that pull cool outside air into the greenhouse through the side vent as warm air rises and exits through the top vent. The combined side and top vent area should equal about 20 percent of the roof area. Vents can be manually controlled, but this means you’ll be constantly adjusting them as outside temperature and conditions change. Another option is using a thermostat paired with an electric motor or auto-opener. A single set-point temperature determines when an automatic system opens and closes your vents. More advanced systems open and close vents in stages based on multiple set-point temperatures. Natural flow-through ventilation costs less than forced-air ventilation to operate; however, it may not be adequate to cool the greenhouse during the summer or in hot climates.

Forced-air ventilation systems use a louvered intake vent and electric fan, or multiple fans, controlled by a thermostat. The fans take cool air into the greenhouse from outside through an intake vent and push warm inside air out. Fans should be mounted in a waterproof housing with air-activated louvers to protect electrical components from inclement weather and to keep cold air out during the winter. Be sure to install a screen over the inside of the fans to prevent injury and to keep out airborne pests. Be sure that the distance between the fans and adjacent structures equals at least 1-1/2 times the fan diameter.

You’ll want to be sure that your fan capacity is large enough to exchange the air in the greenhouse at least once per minute. Recommendations for warm climates call for a fan capacity to remove 12 to 17 cubic feet per minute per square foot of floor area. If the greenhouse is attached to the east, west, or south wall of another building, solar heat will collect inside the greenhouse from this wall. If this is the case, add half the area of the attachment wall to the floor area when calculating the ventilation requirements. Work with a greenhouse supply or construction company to determine the proper size fan or vent for your situation. 

How to Grow Tomatoes in Your Greenhouse You can grow one plant in a 6-inch pot or two plants in larger pots. For a continuous winter supply, start one or two new plants from seed every two weeks. Recommended varieties are Pixie, Patio, Toy Boy, Small Fry or Tiny Tim. These varieties will produce small plants, but they still may need to be staked, especially when they begin to bear fruit. Quarter-inch dowels make good stakes. Germinate seeds in a small pot with starter mix. Plant seeds about 1/4 inch deep and water. Keep starter mix moist but not soggy. Germination should occur in 5 to l0 days. Transplant from starter mix into potting soil when seedlings are about 3 inches tall. Fertilize regularly, but lightly, beginning about two weeks after transplanting. Water plants thoroughly, but not too frequently. Since there are theoretically no insects inside your greenhouse, when plants bloom, help Mother Nature along: Tap the main stem and larger side branches with your finger. This moves the plant slightly and encourages pollination. As you tap the plant, you might see a small cloud of pollen falling from the open flowers. Turn plants occasionally, so all sides get a fair share of sunlight. After each plant has provided a bumper crop and has become unproductive, cut it off at the base, saving the potting soil for future transplants. Toss the old plant in the compost pile. By following these simple steps you and your family can enjoy fresh tomatoes year round that are free of pesticides, full of flavor and less expensive than store-bought tomatoes! Another very popular way of growing your tomatoes inside (or outside a greenhouse is by using the Topsy Turvy planters which you can hang from the roof of the greenhouse using small clip hooks which attach to the aluminum framework. This is a very efficient way to grow tomatoes and eliminates the problems of tomato plans dropping without a framework for them to be supported by. They are very inexpensive. We found them on Amazon.com for as little as $5.99 each. They are also available for peppers, strawberries and many other fruits and vegetables. Maximize your greenhouse growing space by using this innovative method of growing a variety of vegetables. If you try this and are successful, send us some photos. We'd love to post them on this website. Just email us at info@NorthAmericanGreenhouses.com and include the photos as attachments.

The Story Behind Store Bought Tomatoes To satisfy our year-round demand, commercial suppliers plant tomato varieties suitable to production and shipping needs. Often, these tomatoes lack the taste, color or texture that most people prefer. To better withstand shipping, they usually are picked at the "mature green" stage. To complete ripening at their destination, they are gassed with ethylene, a natural plant hormone that is part of the ripening process. A United States Department of Agriculture study found that ethylene gas has no effect on the tomato's nutritional quality. Surprisingly, such tomatoes provide only slightly less beta carotene, which the body converts to vitamin A, and vitamin C than the tastier vine-ripened fruits. One 5-ounce tomato -- whether home-or-greenhouse grown -- provides a third of our daily needs for these vitamins, along with some iron, fiber and B vitamins. However, our experience in tasting store bought tomatoes it that they have about as much flavor as a piece of round cardboard! In addition, although many of these tomatoes are grown in the US (California, Florida, etc.) one has no idea what chemicals the grower has used in producing these wonderful looking, but tasteless produce.