Gardeners in cold climates need a way to protect the crops they are growing during the winter months. Greenhouses, tunnel houses and cold frames are all great choices for doing this, but what, exactly is the difference between the three of them?

Think of a greenhouse as a small room made out of glass or plastic. The walls and roof are generally clear, although this is not always the case. Electric fans, heaters and automated watering devices are usually an essential part of a greenhouse, although not always. The idea behind a greenhouse is that you control the temperature inside it making it possible to grow plants, such as orchids or other tropical plants, all winter long even in cold, northern climates.

A tunnel house is very similar in size to a greenhouse, but it is unheated. These tunnel-shaped structures are usually covered with clear plastic. Depending on the design of the tunnel house, the sides may raise and lower to allow adequate ventilation into the structure. Tunnel houses are the ideal structure for growing cool season crops all winter long because you can walk into them. This makes harvesting crops nicer.

A cold frame is the simpliest of these structures. It is nothing more than a box-like structure with a clear glass or plastic top. It can be square, rectangle or any other shape you wish it to be. Cold frames are easy to make at home using four bales of straw and an old window. These structures are unheated and used to protect cool weather crops over the winter. They are also useful for hardening off indoor grown seedlings. Hardening off is the process that occurs when seedlings or plants are gradually exposed to weather elements they are not accusomed to. If this process is done too fast, the seedlings or plants could die of shock.

Is it necessary to heat a garden structure during the winter months to keep the plants inside alive?

The answer to this question depends on what you intend to grow. Cool season crops and perennial plants do not need heat to survive the winter inside a garden structure. This is why tunnel houses and cold frames are such popular items.

Are garden structures expensive to buy or build?

Some garden structures run thousands of dollars, while others cost less than $25. The cost depends on what you want. It is possible to build a large greenhouse for under $1,000. That same greenhouse, bought through a greenhouse company, could run $5,000 or more.

If you want to know more about year-round gardening or gardening structures, The Complete Idiot’s Guide to Year-Round Gardening, is a great book that covers all aspects of gardening indoors and out, all year long.