Extend Your Harvest By Building A Garden Cold Box
If you're like me, you wish fresh garden veggies lasted all year long. Thankfully, there's an easy way to prolong their growing season. Adding a cold box, or cold frame, on top of your raised garden helps extend the life of your produce and allows you to keep harvesting vegetables long into the fall.
Step 1: Measure the size of your raised bed. This allows you to make sure the cold box will fit securely on top of your garden and completely cover your produce. If you don't have a raised bed built, follow the first part of my square foot gardening tutorial here.
Step 2: Cut pieces of wood for the base frame according to your measurements. You will be building a rectangle or square cold frame that will fit exactly on top of your raised bed. Nail your cut pieces of wood together using 3" nails and the FiskarsIsoCore 20 oz General Use Hammer (15.5") to create your base frame. I used untreated plywood to build my frame.
Step 3: Cut pieces of wood for the sides of the box. Next, cut what will be the back upright pieces of your frame to measure 24 inches and the front upright pieces to measure 12 inches. This will create an angled box, slanting higher in the back. Using 3" nails, hammer these cut boards to the bottom base frame.
Step 4: Cut pieces of wood to join all upright wooden planks together. Measure the distance between the four upright planks and cut boards according to those measurements. Using 3" nails, hammer the boards in place to create your final box, which should look like a rectangle at the base and a raised quadrilateral on the sides. Place the built frame on top of your raised bed to ensure the frame fits correctly.
Step 5: Cut plastic to size and adhere to cold box frame. Lay out the plastic over your cold box to find the needed amount to cover the frame from front to back, leaving the two quadrilateral sides open. Cut off any excess plastic using the Fiskars PowerArc Easy Action Shears (10").
Step 6: Nail plastic to cold box frame. Attach the cut plastic to the cold box frame using 1/2 inch roofing nails. Be sure to pull the plastic tightly across the top, front and back sides so the final covering is taught against the frame, and again trim any excess plastic, if needed.
Step 7: Place cold box in final position. Once you have finished the construction, ensure the cold box is in the correct location over your raised bed. It will act as a greenhouse and keep your plants warmer during those cold autumn nights.