Crisp kale, savory bok choy, and tasty arugula are all great when they are fresh from the garden in the summer, but how good would they taste in winter?
Enter the endless possibilities of a cold frame.
What Is a Cold Frame?
A cold frame is really just a mini greenhouse. By protecting your plants from excess cold and frost, a cold frame extends the growing season of greens and herbs.
This cold frame is uniquely designed for manufactured homeowners who rent their lot in a home community, apartment dwellers with porches or anyone else who has access to the outdoors but does not want to dig up a garden.
By using a reclaimed window and the right finish, this project makes a great shabby-chic addition to any country home or city apartment!
If you have a family member or friend with a work shop, this would be a good project to include them (and use their space). However, this can certainly be built in a weekend with a little patience and a comfortable work area.
- Cordless drill
- A good hand saw
- Surform (for minor adjustments after cuts)
- Framing square
- Speed Square
- 4 bar clamps
- 3 1”X6” boards at 6ft.
- 1 1”X4” board at 6ft.
- 2 2”x4” studs at 8ft.
- 1 2x2 foot section of ¼ in. plywood.
- A box of 2¾ in. drywall screws
- Stain of your choice
- Two door hinges and a pull handle
- Reclaimed window with non-lead paint
Step 1. Build The Growing Box Frame For Your Window
My window (acquired at a Habitat for Humanity ReStore) happened to be 26 ¼ in. by 19 ¼ in. So, I built a bottom layer of the box with the 1”x6” stock to those dimensions.
Now for the trickiest part of this build. To build the “top layer” of the growing box, you’ll need to cut a taper on the two shortest sides to angle the box south, where it will get the most sun on short fall and winter days.
If you have a jig saw or table saw, you won’t have any problem. I don’t own either, so I just used a handsaw.
Start by putting a mark 4 in. from the edge of a 1"x6" board.
Then, use your framing square to draw a line from the other edge to that point, as pictured below.
Now, clamp your board against a bench or in a vise and start sawing, paying extra close attention to the beginning part of the cut. If you get a good start and focus on cutting on the line, you should have no trouble cutting these two pieces out.
Step 2. Cut the Legs
A standard workbench is around 30 in. high. I’m a little taller than most, so I went with 36 in. legs for comfortable harvesting without bending over.
Cut four legs at 2 in. below your desired height. Then clamp the legs to rest 8 in. into your box from the bottom. With screws, attach the box to the legs to make sure the legs are attached to the two “layers” of the boxes.
Step 3. Install the Bottom
At this point, you should have something that looks like the picture below.
Now it’s time to put in a bottom. I only plan on having a few small pots of herbs and greens, so I went with ¼ in. plywood, but upgrade to ½ in. or thicker as you see fit.
Start by making corner brackets from your 1x6 scraps with a square.
Then, measure and cut two 2”x4” studs to brace the inside of the box and add more surface area to attach the floor.
Put a bead of glue around the 90° corner of the bracket and attach with screws to the 2”X4” brace and the leg.
Finally, using a framing square, plot and saw the dimensions of your plywood to lay flush with the sides.
You can glue it down, but it is not necessary as long as the brackets are properly braced.
Step 4. Install Window and Finish
If you have done everything right, your window should rest flush on the box. Find where you want your hinges and install on the back using their hardware.
On the front, find your center point and install the pull handle there.
Finally, stain and finish with whatever color you like. Since this will be exposed to the elements, it’s essential to use a natural finish like linseed oil or polyurethane sealant to protect the wood and stain.
Using your Cold Frame
There are lots of different ways to use this cold frame. Look at different growing resources for tips depending what kind of plants you want to grow in your cold frame!
However, there are a few best practices.
- For one, use a wooden dowel or scrap wood to prop the door open when a day is going to get above 70° to allow proper ventilation.
- Second, face the front of the box South. The afternoon sun is the longest, so the designed taper will expose your plants to more life giving sunshine.
- Finally, remember to use your cold frame in the spring. March, and sometimes April, always brings a final frost that can kill the hardiest of seedlings, so start small plants in the cold frame until the final frost for a longer growing season into the summer!