Want to get planting earlier, warm the soil, protect starts as they harden off? You need a cloche or a cold frame. I have just the thing: an easy tunnel cold frame that you can build without much cost or skill.
First, go window shopping. Not peeking in windows of downtown stores — shopping for windows at building salvage places. A great one in Seattle is Second Use, where I’ll be leading a workshop this Sunday on this very topic.
Second Use, the ReStore and similar shops in many cities are great places to find inexpensive materials for garden building projects. They reclaim old window sashes and doors when homeowners are doing remodeling. They also have random collections of building materials, like wood or stone for raised beds, pipe for cloches, mesh for trellises and even old bathroom fixtures you could plant in, if you want. For the sake of your neighbors, please try to resist.
So here are the basics of a simple, lean-to window tunnel.
Find two window sashes of the same size.
Aluminum-framed ones are great, because they’re lightweight, and won’t rust in wet weather and soil contact. But they’re hard to find. Wood window sashes are great, with a couple of caveats. Find ones with solid putty that holds the glass securely. Look for recent ones that don’t have peeling paint. Older windows, before 1973, will likely have lead paint, and that can flake off into your garden, and is a hazard for the environment, you, your kids and your pets.
I’ve found some glass-fronted cabinet doors that work great. It’s less likely that lead paint was used on interior projects, and these are varnished on one side. They’re not real large, but big enough to grow a three-foot row of something, or to easily cover one flat of seedlings.
Carefully drill two small holes into the edges of one side of the frame. Into those, screw round eye hooks. These should match on each window, so when you lean them together in an A-frame shape, the eye hooks almost touch.
Set up the windows on a garden bed, then run a heavy-gauge wire through the eye hooks and twist it up to hold the windows in place. This will prevent them from collapsing into the bed and crushing your plants.
On each end, pile straw to cover the triangular-shaped hole. This will provide enough protection from wind, and will help hold in the warmth that will have been gained during the day. You could also lean full bags of mulch against each end, or find some other way to block those openings.
For a warmer solution, cut a piece of 6-mil plastic to fit each end, stretch it tight and staple it on. Or even cut triangular plywood ends and screw them into place. Adding something permanently to the end makes it more difficult to move the cold frame or take it apart for storage.
This simple building project will raise the soil temperature under the windows by 5 degrees or more, helping you plant earlier and provide a warmer environment for seedlings. Just don’t forget to water, and look at it daily to make sure it’s working properly.
Want to see more ideas and shop for salvaged products? Come to my talk at Second Use on Sunday, April 6 at noon. Better yet, come early and shop the plant sale that is accompanying the event. I’ll show slides of many ideas, give a couple of demos, and then we’ll walk the store to find the hidden treasures.