Season Extenders: Cold Frames

In a previous post, I briefly mentioned the benefits of a cold frame. In Flagstaff, they are essential if you want your perennial plants to survive the winter (like my herb garden) or if you want to grow cold tolerant lettuce (like Arugula, Sorrel, Spinach) throughout the winter or early spring.


The cold frames above are made from a salvaged screen door with glass (see cold frame in the background) and a double pane window (see cold frame in the foreground). Paul added insulation board to further protect the plants. In the winter, you can close the cold frames for the duration of the season. During the spring, venting is a must. Temperatures can rise quickly to 120 degrees F.

Below are pictures of the herb garden and the lettuce garden which have been protected by the cold frames the entire winter. Lisa Rayner of Growing Food in the Southwest Mountains suggests to use rocks to add more thermal mass to your garden. It works. You will see how rocks are used in the picture below.

Thyme, Sage, Fennel, Oregano

Arugula and spinach with some green onions interspersed.