How to Make a Simple Cold Frame

Large cold frame.

A cold frame is similar to a small greenhouse. Gardeners use cold frames to harden off seedlings for spring planting. Building a cold frame will also extend your growing season. In some climates, a cold frame can make it possible to grow vegetables year-round. Cold frames can keep plants up to 10 degrees warmer than outside air. Cold frames can be constructed from a variety of materials to suit the needs of almost every gardener.

Things You'll Need

• 2-by-2 cedar boards
• Plastic or vinyl sheeting
• 3-inch corner brackets
• Staples
• Plywood
• Screws
• 5-inch T-hinges, 3
• Paint or stain
• Paint brushes

Instructions

1. Lay the two, 4-foot boards horizontally on work surface. Lay the three, 3-foot boards vertical, two on the sides and one in the center. Connect using 3-inch corner brackets and screws, on all four corners. Use screws to attach the center piece to the main frame. Staple plastic sheeting or vinyl to the frame.

2. Cut two pieces that form the sides. With a 3-by-3 piece of plywood, measure 18 inches up on one side. Mark location, snap a chalk line from the 3-foot side to the 18-inch mark on the other side. Cut the piece along the angle. Repeat for second side. For the back of the cold frame, cut a piece of plywood 4 feet wide by 3 feet tall. For the front, cut a piece of plywood 18 inches tall by 4 feet wide. Attach the angled sides to the front and back of the frame with screws.

3. 

   Use screws, not nails to attach the hinges.

   Using screws, attach three 5-inch T-hinges to back of frame and the lid.

4. 

   Paint the interior white to reflect sunlight onto the plants.

   Paint or stain plywood for a neat finish. Paint the interior white to help reflect sunlight onto growing plants.

Tips & Warnings

• Prop-up lid during the daytime to prevent burning the vegetables.

References

• Mother Earth News: Use Cold Frames to Grow More Food
• University of Missouri Extension: Using Hotbeds and Cold Frames