A cold frame is a low, bottomless box with a transparent, hinged lid that traps solar heat to protect plants from cold and extend the growing season.
Inputs
- Materials: a wood, cinderblock, or brick frame no more than 90 cm deep, with a glass, rigid-plastic, or fiberglass lid mounted on hinges, sloped higher in back (about 45 cm) than in front (about 30 cm) to admit more sunlight.1
- Siting: placed over well-drained soil, lid facing south, with the north end set against a building or fence to reduce heat loss.1
Type
Functions
- Frost protection — extends the growing season by about 2–4 weeks in both spring and fall; the sash is raised when inside air exceeds 29°C and the lid is closed before sunset to retain heat overnight.1