Cold Frame Greenhouse

cold frame in the snow on side of houseCold frames are the smallest form of greenhouse, and the best place to start for the sprouting greenhouse farmer. You may be able to put together a cold frame today with simple materials you have lying around.

An old bathtub with a shower door on top would make a fine cold frame. Or you could stretch a spare scrap of clear plastic over a cardboard box. I’ve even seen gardeners cover a struggling plant with an upside-down glass dish or large mason jar as a tiny makeshift cold frame.

You could build a heated cold frame with a straw bale and an old salvaged window. It keeps your plants toasty warm through the heat produced during decomposition. As the straw bales compost, they heat up – in some cases so much so that they start to smoke!

Cold frames are most useful for hardening off seedlings that have been started indoors or in a heated greenhouse. Most plants should not spend their entire lives in a cold frame. As always, first decide what you want to grow, then choose your greenhouse strategy based on your crop’s heat and space requirements.

Raised cold frames are becoming popular because they are easier to access and do not require their  user to squat or kneel. Make sure if you are designing a raised cold frame you make your legs strong enough to support  your chosen growing medium.

A cold frame is not a very productive way of farming, but it’s the best first step. If you can make all your mistakes in a cold frame, you won’t make them in your high tunnels!

Free Cold Frame Plans

Courtesy of Tipnut.com:

  • Recycled Window Cold Frame Made with an old window, cedar fencing, cedar decking and 1×2 cedar. Hinges and a carriage bolt are attached to open and close as you like.
  • Polycarbonate Cold Frame 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.
  • Ikea Shelf Cold Frame Made with repurposed Ikea shelving and lined with rigid sheets of styrofoam insulation. Top is protected with plastic sheeting.

See more on Tipnut’s Cold Frame Page