I mainly use my cold frame to start seed pots and to harden off bedding plants a little earlier than my zone normally allows. They do work like a charm for that purpose.
Some folks also place them right in the garden to cover new seedlings they’ve planted early, just situating the frame over top of the patch. When the nights are warm enough, lift it off and put it away until next year…or use in the Fall to prolong the last few weeks of harvest.
These nifty boxes are small but mighty…depending on the zone you live in they can extend the growing season by up to six weeks (on each end Spring and Fall).
They are usually pretty basic with just a wood frame and a clear glass or poly cover (there’s no floor, just the bare ground). Keep the lid open during the day when it’s sunny then close it at dusk to keep the little seedlings warm through the night and to protect from frost.
I’ve been searching online for a few simple tutorials/projects that are free, use recycled materials and are easy to understand…but it’s been a tricky task. A few of these come close since they use old storm windows or glass doors, while others are more advanced projects but still worth a look or two for the inspiration they provide.
For the short amount of time you’ll be using one, I wouldn’t fuss with anything too elaborate or expensive (unless you are making one as a feature in your garden).
If you’re wanting something on a larger scale, I do have a collection of Greenhouse plans on this page (also free).
Quick Note: This isn’t a DIY project, but if you have a tight space and are looking for a vertical solution, see this article at theguardian.com. It’s about investing in a ready-made option (vertical cabinet), maybe it will spark an idea for you to hammer something out for yourself.
Now on to the cold frame projects…I’ll be adding new tutorials to this page as I find them, have fun!
Simple & Cheap: Simple design and made with recycled materials such as a sliding glass door (or any piece of glass) and framed with wood. Simple hand drawn plans available.
Quick & Easy: A roomy 32 square feet, this is made with SUNTUF polycarbonate panels and lumber. Top is hinged and frame rises toward the back for taller plants.
With Bench: This one’s pretty neat, the box is raised on four legs and has a shelf on the bottom to hold garden supplies.
Knockdown: This one’s designed to be setup and taken apart in minutes so it can be easily stored during the off-season. Simple frame consisting of five pieces.
Twin Top/Lid: Top lid slants at an angle, this one has two sides. Suggests repurposing a shower door or use a sheet of twinwall polycarbonate.
Window Sash: If you don’t have any spare sashes, you can frequently find overstock for sale at your local lumber store. This one is small enough to reach into but large enough to make a difference.