GardenDesk

The Cold Frame is the Gardener's Best Investment!

I am beginning to plan this year's seed starting schedule. I plan to re-build a basement light stand set-up similar to the one I used to have. Many of those seedlings will then move out to my hoop house, but in March, it sometimes still gets too cold in there. My solution? I will put my cold frames inside the hoop house for extra protection.

This will be done in a similar way that I used to put seedlings in the cold frame out in the garden in April and May. Thinking about my cold frames reminded me that I should write about the benefits of cold frames.

Not every gardener can have a greenhouse, but they all should utilize at least one cold frame. I consider the cold frame the single best garden investment, but many people don't know about them.

I want to start with showing you one of my basic cold frames.

I build mine by following the plans from one of my favorite old books,
The New Victory Garden which costs almost nothing if you buy a used one on Amazon.

So what exactly is a coldframe and why should you have one?

A cold frame is essentially a bottomless box with a covering of glass or clear plastic sheeting. These coverings are called "lights" because they collect the warm sunshine to heat up the plants contained inside the frame. This "box" can be placed directly over a portion of your garden bed to protect plants that are growing in the ground. You also can simply use your cold frame to place potted plants inside. The "lights" are constructed on the top of the frame at an angle - usually somewhere between a slight angle to a 45 degree angle, facing south to maximize mid-winter sun.

I consider a cold frame the gardener's single best investment because it enables you to extend the growing season for several months. In many areas, a cold frame will aid you in growing cold-season greens all winter long. The more months I can provide my family with healthy organic vegetables, the more money I save!

The cold frame is not a new invention. It dates back to the beginning of cultivated farming. It is very versatile because you can build it to suit your space and your needs. It can be any length as long as you can get the tops to fit. Many times you can construct one out of recycled or reclaimed materials such as old storm windows. My first cold frame was made from an old shower door. I do have to pause here to issue a warning however. Keep in mind that if you use glass as the "lights" that it can become dangerous if someone steps or falls onto it. I switched to using greenhouse style plastic sheeting when I had small children "helping" in the garden. Always remember, safety first.

So how does the cold frame work?

It protects plants from wind and freezing. When the lid is closed, it creates a micro-climate with the temperature being higher than the outside temperature. Granted, the difference may only be 5 or 10 degrees different in the winter, but that is significant when you also cut down the wind and the moisture that leads to freezing.

So what are the primary uses for a cold frame?

• In the spring, you can start cool-season vegetables earlier.
• In the fall, you can keep cool season crops growing longer.
• In winter, you can keep root vegetables and cold tolerant greens from freezing. This gives you an extended harvest!
• In the spring you can use your cold frame to harden off flower and vegetable plants that you started from seed indoors. This is another way to save money. You don't have to buy your plants from a garden center.
• In spring and early summer, your cold frame can be your nursery for growing new seedlings.

If cold frames are so good, why doesn't everyone use them?

Mainly I would have to say it is because they haven't fully considered the benefit of having them in the garden. Another reason could be because of the extra work it takes. Yes, they do require some extra work. The drawback with using coldframes is that you have to constantly be aware of the weather outside. A coldframe needs to be vented if there is direct sunshine on it or if the temperature significantly rises. The power that we rely on to keep the veggies warm can quickly become powerful enough to cook those veggies.

This is not as much a problem in the middle of winter, but you have to be careful in the spring and fall. If you can't be ready to open or close the frame based on the changing weather, you can purchase an Automatic Vent Opener that will do it for you. I would love to have one, but we have always watched to venting needs ourselves. I do admit however that in the Spring I am always wondering how the plants in the cold frame are doing. When hardening off vegetables in late Spring, we keep a sensor in the frame that broadcasts the temperature to a remote thermometer in our kitchen. When we notice the temperature getting too hot, we open the lid further. If we get an unusually hot and sunny day, we take the top off entirely. It can actually be fun trying to figure out what the weather will do. The venting requirements vary depending upon the season. On most days there are no problems at all. Even when it gets tricky, the benefits still outweigh the hassles.

I strongly encourage you to use a cold frame to help you grow more food for an extended period. If you have used them in the past, but haven't lately - now is a good time to re-consider them. If you have never used them before - now is a good time to make yourself a small frame. You can see a very simple design on my post Step by Step How to build a Cold Frame.

If you are like me and it is winter where you are, building a coldframe while it is snowing outside will make you almost forget the cold and long for warm gardening ahead!

Keep Growing!

Step by Step How to build a Cold Frame

Last year I posted about the new Cold Frame that I built and I was asked to write a more detailed how-to post. I bought the materials to make another one, but never found time to build it... until now.

Last year's cold frame looked like this:

It was basically a 4'x4' cold frame built by following the plans from one of my favorite books called The New Victory Garden by Bob Thompson.

The new cold frame I built was created in basically the same way but instead of the traditional 48" in depth, I made it 40" so it will fit the raised bed in my new greenhouse. That's the beauty of building your own cold frame - you can tailor make it to fit your needs.

The New Victory Garden was written way back in 1987. It was the first vegetable gardening book that I bought and I learned a whole lot from it! It truly was instrumental in my obsession with veggie gardening. There are many great things in the book including easy to follow plans for how to make a coldframe. I will attempt to explain the steps involved in the remainder of this post, but I'm sure I won't be able to do it as well as Thomson. Let's start with the materials needed:

All you need are some tools, exterior nails or screws, two hinges, a 4' piece of good plastic sheeting, 3 - 8' 2x6 or 2x8 untreated boards, two 8' 2x4s, two 8'a 4' piece of wooden dowel, 10 feet of 1x3" lumber and some furring strips. I'm sure I missed something in that list, but we will go over each step below:

Begin by cutting the 8' 2x8s in half to create six 4' boards:

The boards will basically be arranged like the last panel of the above picture. 4 boards make a box for the bottom layer. One more board goes on top in the back, and the last board gets cut diagonally for the sides.

This is probably the most difficult part of the whole process. Draw a line from one corner to the opposite corner and cut down the line. The way I accomplished this was to clamp it to my table. After the cut is made, you should have two identical diagonal boards.

Next, attach each diagonal piece to one of the side boards with small pieces of the 1x3s. Do the same with the two 4' boards for the back. You can use exterior 3" screws or galvanized nails. I used some of each.

Now that the back and sides have been created, we have to attach them. This is one of my favorite features of the Victory Garden's plan. If you simply nailed the sides together, you would have to build the frame in place because the entire unit would be too heavy to move. This design allows you to easily take apart the frame to move it around or store it.

Each corner is attached by using galvanize eye screws and wooden dowels. You alternate the eye screws in the corners and then slip the dowels in.

Next you build the lid or top of the frame that will be hinged to the frame using 2x4s. The front and back is made from 4' pieces and the sides from whatever length you are making (this frame needed to be 40" total front to back length, so the side pieces were 37"). The most difficult part of this is that the sides need to be cut at an angle so the lid fits securely. The easiest way to do this is by lining up a straight edge with the boards below.

The 4 lid pieces are then attached by nailing through the ends. You might find it easier to use an "L" bracket to line up each corner first.

After the lid is solid, you can attach it to the frame with hinges. Then you can add plastic to the top by stapling it down and nailing furring strips over the plastic.

The thicker the plastic sheeting you use, the better. I used 6 mil greenhouse plastic for this one. Last year I just used plastic from the hardware store and it was probably 4 mil. The book calls for wire fence to be put down first before the sheeting is attached. I did this last year, but didn't think it was necessary for this one. If you do use fencing beneath the plastic, use "U" nails to attach it to the top of the lid.

We're almost finished with our new coldframe now! After you've nailed down the furring strips over the edge of the plastic, trim the excess plastic away. Then you need to measure the middle of the front and drill a hole in it. This will be used to slip a carriage bolt through to attach a post that will allow you to vent the frame when needed.

My finished cold frame looked like this:

All ready to be taken outside and put in the greenhouse. It will soon house tender young plants to help me get a jump on the growing season. If you want to know more about the uses of a cold frame, see my new post, A Cold Frame is the Best Investment, or visit the library and get some books about it. There are many books available that include ways to use cold frames for season extension. Among my favorites are Four-Season Harvest by Eliot Coleman, Solar Gardening, Growing Vegetables Year Round by the Poisson's, Gardening Under Plastic by Bernard Salt, and my new favorite where I got our greenhouse plans from - The 12-Month Gardener by Jeff Ashton.

Now I just have to do more seed sowing! Oh, I almost forgot to mention the final step in building a cold frame - sweep up the saw dust and add to your compost pile :)