Gardening Under Glass

Gardening by the Yard : Episode GBY-413 -- More Projects »
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The ideal site for a greenhouse is a south to southeast exposure. Paul James' unit faces south. (Click to enlarge.)

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A reinforced concrete footing that extends four inches below-grade helps give this greenhouse a secure foundation. The base plate of the greenhouse is fastened to the foundation with bolts.

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Paul James could have poured a solid concrete slab, but instead the floor is nothing but a single sheet of landscape fabric covered with mulch.

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A roof vent helps cool the greenhouse. This vent functions automatically, opening and closing when inside temperatures reach preset limits, which are adjusted by thermostat.

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The heater is also thermostatically controlled.

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Shadecloth is essential for helping to reduce heat inside James' greenhouse during the summer. The cloth cuts light transmission by half, but it alone won't keep the greenhouse cool enough.

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An evaporative cooler provides temperature control in the summer.

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A simple fan promotes good air circulation and helps reduce the risk of fungal diseases.

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A minimum-maximum thermometer lets James know how hot or cold his greenhouse gets each day.

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These benches come in a variety of stackable sizes. Made out of recycled plastic, the benches should last a long time.

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Inexpensive hangers will hold hanging baskets.
Tomatoes in January, a host of orchids in February, humidity-loving tropicals in the middle of an arid climate. If you yearn to garden year-round, there's nothing like a greenhouse that lets you garden no matter the location, climate and season.

"I'm always looking for new ways to garden," says master gardener Paul James. "This year, I finally get the chance to garden under glass."

James introduces the essentials for a well-equipped greenhouse:

  • Location, location, location. The ideal site for a greenhouse is a south to southeast exposure so it can capture all the available light.

  • As with any structure, a good foundation is crucial, especially where winds are strong. To follow James' model, pour a reinforced concrete footing that extends roughly four inches below grade and four inches above. Use bolts to secure the base plate of the greenhouse to the foundation. For the floor, you can pour a concrete foundation or simply lay down a single sheet of landscape fabric, and cover it with mulch.

  • One of the most important things to consider when planning a greenhouse is the type of overhead glazing or covering material used. The least expensive is plastic sheeting, but you'll need to replace it every two to three years. Rigid polycarbonate is another choice, and although it lasts a good deal longer than plastic sheeting, it tends to yellow over time. The most durable and expensive of all glazing materials is glass--specifically, tempered glass. No other material captures more light, especially precious winter light.

  • If the greenhouse will be used year-round, consider your climate. In the northern border states, heat will obviously be required in the cold months, but a cooling device for summer may not be necessary. In the Deep South a greenhouse must be cooled but probably will not have to be heated. In the nation's midsection, both heating and cooling are a must for gardening throughout the year.

    Even when the temperature outside is really cold, so long as the sun is shining, the temperature inside the greenhouse can soar. As a matter of fact, for a glass greenhouse, the outside temperature may be 32 degrees and the inside temperature may be close to 100 degrees.

    For gardeners in all but the most northern climes, controlling temperature during the summer months is essential and usually requires more than one cooling device. Roof vents and shade cloth help reduce inside temperatures; an evaporative cooler does the rest.

  • To produce strong, healthy plants and reduce their risk of infection from fungal diseases, install a good fan to improve air circulation. A minimum/maximum thermometer is also required.

  • Benches of various heights will be needed to set plants on. One should be counter height and designated as a potting bench. Some growers prefer wooden benches, but insects can overwinter in the wood, so many gardeners have switched to plastic.

With a greenhouse in place, winter is no deterrent--orchids and other tropicals and warm-season veggies such as tomatoes and peppers are just a step away.

Resources
greenhouse
National Greenhouse
10983 Leroy Dr.
Northglenn, CO 80233
USA
Toll Free Phone: 800-303-1543

greenhouse shelves
Structural Plastics Corporation
2750 Lippincott Blvd.
Flint, MI 48507-9830
Phone: 810-743-2800
Toll Free Phone: 800-523-6899
URL: www.structuralplastics.com
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