Pseudo’ Cold Frame - PCF

by Susy Spence

Horticulture Chair

This time of year as we put our gardens to bed outside, I have a longing to perpetuate the flowering! How about you?
A number of years ago my husband and I began experimenting with a portable style cold frame that we call a pseudo cold frame (PCF.) We put the PCF on our patio up against the back of the house which had a southern exposure. The heat of our brick house and the heat of the concrete plus the addition of a light bulb created just enough heat that we could winter over favorite hanging baskets, pots of agapanthus, a few geraniums from summer, callas and amaryllis, and a wide assortment of not-so-hardy plants over the years.
A traditional cold frame sits on the ground and pots are placed in it at ground level or partially dug into the ground and insulated with a layer of leaves. Properly watered in the fall, not much else is necessary until early spring. Bulb forcing can be done in a traditional cold frame and cuttings of plants and shrubs can be protected through a first winter this way. There are lots of possibilities.
Our PCF is one that you can tend all season. Its location on the patio makes it easy to check on every few days; so if one of those geraniums starts to bloom, you can bring it into the house and enjoy it. When we go out to feed the birds we can check on it - even open it if Mother Nature has given us one of those welcomed warm winter days.
We have learned from our mistakes through the years. Having lost my miniature geranium collection one cold day when the light bulb burned out, we now always have two light bulbs.
The structure is the same as a regular cold frame with the back higher than the front to allow more winter sun into it. We started out covering it with an old window. When it broke, we jerry-rigged a wood frame with two layers of frosted plastic around it. We’ve used that ever since. It’s much lighter to lift than the glass window. We make a new one each year. If it gets windy, we use bricks to hold it in place. If the temperature really drops at night, we throw a plastic tarp on it for extra protection.
Our PCF is a wood structure that comes apart each spring and is stored in the garage until fall. Two ‘trouble’ lights and 100 watt bulbs provide the heat. An outdoor weight extension cord with a portable GFI (Ground Fault Interrupter) on the cable is needed to insure safety. Styrofoam sheets can be cut to size to line the inside. The dimensions are 18"x 48" in front and 27"x 48" in back.
At our current home, we have no concrete patio so our PCF has been taken to the back of a flowerbed up against the house - southern exposure again. Here we have stacked bricks to form a facsimile foundation for the PCF. That actually remains in place through the summer and is barely visible once the peonies and fairy roses are doing their thing.
It’s so much fun to have a geranium blooming on my kitchen counter in the winter! Try our PCF and enjoy having some of your summer garden to brighten your days this winter.