I mainly use my cold frame to start bedding plants a little earlier than my zone normally allows and they do work like a charm for that purpose. If you’d like to extend your growing season, these are an ideal solution. I’ve been searching online for simple, cheap plans that 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. I’ll be adding new projects to this page as I find them, enjoy!
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.
Ikea Shelf : Made with repurposed Ikea shelving and lined with rigid sheets of styrofoam insulation. Top is protected with plastic sheeting.
Also see this DIY Cloche for Seedlings : Garden cloches help protect seedlings from the cold so this is another option for extending the growing season. This easy project wraps a wire hanging basket with filmglaze.
You might also find this article on Fine Gardening interesting: 4 Ways to Use a Cold Frame .