An unheated structure with a transparent lid (glass or polycarbonate) used to protect plants from frost and wind. Creates a microclimate several degrees warmer than ambient, extending the growing season.
Cold frames are invaluable for Australian gardeners in climate zones 6-8 and elevated regions where winter temperatures drop significantly. They're typically constructed from wood or recycled materials with a glass or clear polycarbonate lid that allows sunlight penetration whilst retaining warmth. During autumn and winter (March-August), cold frames protect seedlings and young plants from frost damage, allowing you to grow vegetables like lettuce, spinach, and Asian greens outside their normal season.
In spring (September-November), cold frames harden off seedlings before transplanting into the garden bed, and they can extend the season for cool-season crops. The simple design makes them easy to build from old windows and timber, or purchase ready-made from Bunnings. Proper ventilation is essential—prop the lid open on warm days to prevent overheating and allow air circulation. In warmer climates (zones 9-12), cold frames are less critical but remain useful for protecting sensitive plants during occasional frosts.
Position your cold frame in a north-facing location to maximise winter sun exposure whilst providing afternoon shade in spring. Water plants early in the day and ensure good drainage to prevent fungal issues in the humid environment. Cold frames are economical alternatives to greenhouses for small-space gardeners and apartment dwellers wanting to expand their growing capabilities.