The greenhouse effectWith Colorado’s ever-changing weather and Coloradans’ love of gardening, building a small, backyard greenhouse could be the answer to yourplanting prayers. For less than $250 you can build a simple yet sturdy greenhouse that meets the needs of the serious grower.

Selecting a sight

Hoop house

OTHER TYPES OF GREENHOUSES

Cold frame

Select a level, well-drained area witha partial amount of shade to avoidoverheating. It’s best to have easyaccess to water and electricity.

A cold frame is an enclosed structurecontaining soil that sits on top of theground or is buried slightly below groundlevel. The box is covered by glass or othertransparent material to create a well-lit,mini-greenhouse.

The plan consists of a wooden frame with bows ofPVC pipe as the support structure. The bows holdup a plastic covering.The lumber used for the frame should be treatedwith an environmentally safe preservative orpressure-treated to help the structure last longerwhile exposed to the elements.PVC (polyvinyl chloride) pipe is a durable andflexible skeleton that will endure a high-moistureenvironment.

Materials

Select a covering according to the type of plants you aregrowing in your greenhouse. A clear, plastic greenhousefilm is a good start. Also available are milky or whitecopolymer films that limit the amount of heat and light,depending on the growth environment you’re looking tocreate. The greenhouse should be as tight as possible toretain heat and humidity.

How a greenhouse works:

The warmer air rises to thetop of the greenhouse.Cooler air replaces it at thebottom, creating a con-tinuous cycle of warm air.

The heated gound warms theair inside the greenhouse asthe air rises.

Summer sun

Winter sun

Similar to a larger free-standing green-house, the hoop house is a small, semi-portable structure that can be used forfrost protection, starting seedlings andgrowing heat-loving vegetables.

Plastic sheetcovering

12 feet

14 feet

2 feet

Kits average $100 to $150.

Cold frames are used for early plantingof summer annuals and seeds orprotecting tender plants in winter.

The sun’s rays shine intothe greenhouse, heatingthe ground.

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Rising warm air

Hinge set for mountingthe door to the frame

4-by-4 post anchorsthe frame to the ground

Rebar post anchors the PVCroof to the frame and the ground

Locate your greenhouse where it has someshade in summer and winter.

Greenhouse

PVC pipe

Jonathan Moreno, The Denver Post

PVC pipe

Rebar

Tubingstrap

6 feet,6 inches

Want to get plans and materials to buildthis greenhouse? Go to: denverpost.com/grow

Shade

Sources: North Carolina State University CooperativeExtension Service, West Virginia University, U.S. Departmentof Agriculture, howstuffworks.com, Graham Clark;cityfarmer.org and Denver Post research