A miniature greenhouse

The versatile cold frame for year-round gardening, and more

By Wes Henry, Published:

I have discovered in the past several years of gardening if there’s one thing I absolutely will not do without it is the versatile cold frame.

If you want to begin, extend and enhance your gardening season then build or buy and use one. With a little discipline and attention, it is one of the most cost effective home gardening tools you’ll ever own. It can be used to start and/or harden off your own bedding plants, to begin earlier and get “a jump” on the fall garden while the summer crops are ending and extend for weeks the gardening season by growing and harvesting crops from them on the cusp of and beyond winter.

Understand, a cold frame is a miniature greenhouse. Simply, it is a square “frame” or box without a bottom, with a mounted glass or clear plastic cover that slopes towards the front and can be opened or closed at will. Ideally, it is faced to the south to capture the maximum light and warmth of the sun, even on cloudy days!

Usually there is no artificial light or warmth but what the sun and ground temperature provides, hence the name “cold.” The sides are made of insulating material such as wood, and with the earth below are used against outside’s colder temperatures.

Buy or make

Cold frames can be purchased or made. Offers and plans are easily found on the Internet. However, one can be simply made from four bales of straw or hay and an old window placed on top then propped open when necessary to regulate the heat.

However, a sturdier and lasting frame can be easily knocked together with 2x10 lumber with the length and width being to fit the top cover. The sides should be cut at an angle to slope about two inches from back to front. Old windows or a storm door that a friend or neighbor wants to rid themselves of, make the easiest and most cost effective tops.

It is this clear glass or plastic covering magnifying the sunshine that gives the cold frame the ability to create a warmer and more humid environment months ahead and beyond what the natural world at times provides. They also offer protection against torrential downpours that would devastate tender seedlings and allows the gardener a means to regulate the amount of rainfall on the plants.

Face it south

Once purchased or completed, face it south. An enjoyable way to determine which way is actually south is to get up early and with a cup of hot coffee or tea, walk outside and enjoy the morning. Smell the virility, listen to the waking moments, and discover fresh the beginning of a new day.

Then find yourself standing with the sun shining against your left arm and notice then you’re looking south. Point your cold frame that direction. You can then “turn” the fresh earth under it and amend as you would any garden soil, preferably with compost and other organic fertilizers. 

In spring the signs are all around, a waxing moon and the first green of the daffodil footprint where the old house once stood, telling me it’s time to start tomatoes and peppers in the cold frame. Frost-tender, these and other plants such as squash can be started right in the ground and then dig them in clumps after they grow their second true leaves, then carefully separate and transfer them to cell packs filled with potting soil to grow still in the cold frame to transplanting size for the garden.

It takes a bit of attention to keep the temperature regulated, not too cold and too hot. Early (March-April) an old blanket or sleeping bag and a light bulb are very helpful for the brief nighttime cold snaps of spring. If below 40 degrees the added insulation of the blanket will help to keep the temperature inside moderate.

If more freezing temperatures are predicted I add a light bulb inside to keep things aright. I know a light bulb is artificial heat but sometimes it’s a must, but only minimally.

Lift the cover

Remember also to lift the cover to allow the heat not to get too high. Plants can cook, wither, and die in a closed frame under the sun of even a cool spring day. It may only take an inch to keep things optimal. So then a thermometer is very helpful and one that is wireless, where you can know the temperature without going outside is an option, but part of gardening is doing that very thing — getting outside!

Summer is a time cold frames easily fall empty. However, leaving the lid wide open, they are easily extra garden space to grow any number of crops, especially those needing extra care, such as carrots, that can be challenging at first to germinate.

Don’t forget the flowers either. If you wanted to spruce up the garden area a nice overflowing and colorful planting of summer flowers filling the void of the frame looks wonderful. 

With summer’s sun at its hottest I have found another creative use for one of my frames. Being a beekeeper, too, I have been able to use it as a solar wax melter. After the honey crop has been harvested I am left with the wax cappings and with a few added implements I place the wax under the closed lid, which then melts, and by gravity flows through a fold of cheesecloth to a waiting container while I’m away.

That’s leverage, folks!

The cleaned beeswax is then used in candles and for numerous other items and uses.

Thinking of fall

In late summer it’s time to begin thinking of fall.

While the garden space is still limited, with your cold frame you can plan and begin growing your cool season crops like broccoli, cabbages, kale, and lettuces to transplanting size so when those last beans are picked and the vines pulled from the garden no time or expense is wasted punching them into the ground. 

As in summer the cold frames can easily set empty in late fall and on through winter. Yet there’s no reason for such idle space. Use to grow the last of the season’s lettuce, scallions (green onions), greens of all sorts, and radishes or spinach well into the colder months and possibly deep into winter depending on the severity of the season.

Using that space instead of that in the garden will also allow the gardener the temperate time to get good stands of beneficial cover crops on those areas when otherwise they would be challenged to do so because a fall crop is still growing in them and after harvest would leave them then detrimentally winter-barren.

There is much more available to read and to learn on how gardening with cold frames can be year round, even in the least of moderate climes. Hopefully, your appetite has been whetted for trying your hand using this most versatile and economical of tools in the ever-interesting garden.

Without cold frames, I have realized how completely subject I would be to the whims of the natural world, but with them a gardener is more capable to learn and utilize the rhythms and means of the creation around and above us all, which are made available to us all.

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