Tomatoes growing inside a cold frame in my Indiana garden on November 11, 2011.

See the vegetables that are still growing and being harvested under cover in Indiana in November.

Learn how easy it is to make your own cold frame! No buidling required. If you can cut plastic, bend hoops and use clips to secure everything, you can make your own cold frame!

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.

There’s nothing quite like picking your own tomatoes on January 1, 2011! Today is also the first day of the year that gardeners can sow carrot seed under cover. The first video is of carrot seed being sown and the second one is of the tomato I found under the frost cover in the cold frame.

Seed starting time is rolling around in the Midwest once again. If you are seeking early blooms this season, now is the time to start seeds of dianthus and snapdragon.

Also if you didn’t get your pansy and viola seeds started back in November, be sure to start those.

These cool weather plants will do fine, once germinated, in a cool greenhouse. As spring approaches and the weather warms, sometime in mid-March to early April, these young plants can be moved into a cold frame and then on into the garden.

Once they have been hardened off, they are sure to survive light frosts. Should a severe frost threaten your area, simply cover them with a make shift cold frame made out of an old milk carton or two liter plastic bottle. Be sure to vent the cold frame so the plants do not cook when the sun comes up the next day.