If you are looking for a less expensive option to start an early garden or extend your growing season a cold frame is a great option. Greenhouses are great but take a bit of time to build and are fairly expensive. We have raised bed gardens and built a cold frame to fit right in the garden. It’s almost April and I am ready to start growing my Kale, lettuce, snap peas, and broccoli.
First, a list of supplies.
1/2 inch 4×8 treated plywood
4×8 twin panel greenhouse panel (this will be enough for 2 cold frames)
An 8 foot 2×4
(2) 8 foot 2×2’s
(2) door hinges
1-5/8 inch deck screws
2-1/2 inch deck screws for lid
1 inch box of screws for greenhouse panel (they are sold special next to greenhouse panels)
duct tape to tape sharp edges of greenhouse panel
Expect to spend around $80 to build 1 cold frame, but you will have another greenhouse panel for another cold frame.
We used the following tools: circular saw, cordless drill with #2 phillips and drill bit, utility knife, pencil, tape measure, 4′ level (for straight edge to draw cuts)
First cut the plywood, cuts should look like the below
We built ours to be 4 feet long (to maximize the plywood) and 33 inches to fit within our raised bed. 1 foot tall in front and 2 feet in the back.
Now you want to assemble the frame. Use the 2×4’s to attach the plywood. Use the 1-5/8 inch screws to attach sides. The cold frame should now start to look like something!
Now you need to build the frame of the lid. We found the double paned greenhouse panels to resist hail and snow best. Previously, we used plastic and were replacing every year.
Measure and cut the 2×2’s so they fit on top of frame perfectly. Also, cut one of the 2×2’s to put horizontally in the middle of your lid. This will help support the lid frame. Attach the lid frame to the cold frame box with the hinges making sure the lid will be able to open and close easily. Place greenhouse panel over the lid and cut with utility knife. If you are making 2 cold frames be sure to take the size into consideration. Once cut, wrap edges with duct tape. Then fasten the panel to the lid frame with greenhouse screws.
Now you have the finished product! Just move to the garden and start planting seeds. Later we will talk about how to use the cold frame and when to plant.