What Is Cold Frame Gardening?
A cold frame is a low, clear-topped structure that captures daylight warmth and shelters plants from wind and light frost. It is a useful middle ground between open garden beds and a greenhouse. With careful ventilation and watering, it can raise seedlings, harden off plants and extend harvests.
A cold frame is essentially a shallow box with a transparent lid, placed in a bright, sheltered position. It may be bought ready-made or built from rot-resistant timber and clear panels, provided the lid opens safely for access and ventilation. Choose a site that receives winter and spring sun but is protected from strong prevailing winds. Set the frame on level, well-drained ground, with the lid sloping slightly so rain runs off. A south-facing wall can add shelter, although reflected heat may require more ventilation on sunny days. Make sure you can reach it easily, because successful cold-frame gardening depends on frequent checks.
Prepare the base according to how you will use the frame. For hardening off pots and module trays, lay gravel, paving or a firm free-draining surface beneath them. For direct sowing, use a bed of loose, weed-free soil enriched with garden compost. Clean old debris from the frame, wash the panels and check hinges, catches and supports before the growing season. Add labels and a thermometer if helpful, but do not rely on one reading alone: feel the compost and observe the plants. Avoid overfilling the space, as crowded pots restrict air movement and make watering difficult. Keep a piece of fleece nearby for unexpectedly cold nights.
Use a cold frame first to harden off seedlings raised in a greenhouse or indoors. Move young plants into the frame for a few hours on a mild day, keeping the lid partly open, then gradually increase their time over seven to ten days. Close the lid before cold evenings but avoid sealing plants into damp air. This transition toughens leaves and reduces shock when plants are finally planted outside. Start with hardy vegetables and bedding plants, then use the frame for less hardy plants only when temperatures are suitable. In cooler areas, extend the hardening-off period and delay final planting until the last spring frost has generally passed.
A cold frame can also support early and late crops. Sow hardy salads, rocket, spinach, radish, spring onions and beetroot in modules or directly in the frame when the season allows. In autumn, move pots of parsley, chives or winter salads inside to keep leaves sheltered and harvestable for longer. Do not treat it as a heated greenhouse: growth will slow sharply in dark, cold periods. Choose crops that tolerate cool conditions and sow small batches rather than filling the frame at once. Harvest outer leaves regularly, remove decaying foliage and keep the soil surface free of weeds. This keeps the limited space productive and clean.
Ventilation is the most important daily task. Open the lid a little on bright days, even when the air outside feels cool, because sun can raise temperatures quickly beneath clear panels. Prop it securely so wind cannot slam it shut or lift it off. Close it before evening when cold is forecast, but do not leave plants sealed for days in humid weather. Water in the morning, aiming at compost rather than foliage, and check moisture frequently because rain rarely reaches plants inside. In winter, water sparingly while plants grow slowly. Good air movement helps prevent soft, stretched growth and reduces problems caused by stagnant dampness.
Maintain the frame through the year and adjust it to local weather. Brush off heavy snow gently if it blocks light, clear leaves from the lid and repair cracks before rain reaches timber or plants. Shade or ventilate more generously during warm spells, especially in late spring. In summer, it can become too hot for many crops, so use it for hardening off, temporary storage or leave it open. Clean the frame at the end of each season and remove old compost from diseased containers. A well-sited cold frame is simple, but its value comes from attentive use rather than from trying to grow summer crops through winter.
Frequently asked questions
Is a cold frame the same as a greenhouse?
No. A cold frame is lower, unheated and usually holds fewer plants. It offers protection from wind and light frost while using solar warmth. A greenhouse provides more height and capacity, but both need ventilation and regular checks to prevent overheating.
Can I keep the lid closed all winter?
Only during cold, wet or frosty periods when protection is needed. Open it on suitable bright days to release humidity and refresh the air. Even winter sun can overheat a sealed frame, particularly against a south-facing wall, so check conditions often.
What can I grow in a cold frame?
Choose hardy, cool-season crops and young plants being hardened off. Salads, rocket, spinach, radish, spring onions, parsley and chives are useful choices. The exact range depends on your weather, light levels and ventilation, so start with a small trial.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 19 Sep 2026.