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A cold frame gives young plants shelter from rain and wind, but an unheated frame is not reliably frost-free. Successful overwintering starts by separating plants that need modest protection from tender cuttings that require a warmer indoor or greenhouse space.
Table of Contents
Sort plants by their needs
Check the species and variety rather than relying on the word perennial. A hardy young plant and a frost-tender pelargonium cutting do not have the same winter requirements. Recently rooted cuttings also have small root systems and may be more vulnerable than established plants of the same kind.
Label every pot and record where it came from. Group plants with similar moisture and temperature needs so you can care for them without soaking drought-sensitive plants or drying out leafy ones. Take late-season cuttings early enough for the species to establish before winter; a cold frame cannot make up for inadequate rooting time.
Choose a stable, sheltered site
Place the frame on firm ground with good drainage. Avoid a hollow where water collects or a location exposed to strong gusts. The lid must have secure hinges and a prop or restraint suited to the frame. RHS guidance identifies wind as a major cause of damage to small growing structures.
Provide enough light for the plants you are keeping, while recognising that a small frame can warm rapidly in winter sunshine. Leave room to reach the pots without kneeling on the lid or stretching over fragile glazing.
Ventilate when conditions allow
Open the lid during suitable mild weather to reduce excessive humidity and heat. Secure it so a gust cannot slam it shut. Close or adjust it before worsening weather, following the frame’s instructions and the needs of the plants.
Remove fallen leaves and promptly investigate soft, rotting stems. Crowding pots together so tightly that foliage stays wet makes inspection and airflow harder. A little spacing is usually more useful than fitting one extra tray into the frame.
Water the compost, not the calendar
Check individual pots beneath the surface. Winter growth is often slow, so they usually need less water than in summer, but evergreen foliage and small containers can still dry out. Give water when needed and allow excess to drain. Do not leave pots standing in a tray of rainwater.
Use clean water and clean equipment for young plants. Keep leaves as dry as practical when watering in cold conditions, and revisit recently rooted cuttings more often than established dormant plants.
Have a frost plan
Use a maximum–minimum thermometer to learn the frame’s actual conditions. Temporary insulation may reduce exposure, but does not guarantee a safe minimum temperature. Move tender plants to an appropriate protected place before the forecast exceeds their tolerance. Remove opaque coverings when conditions improve so plants regain light and ventilation.
Useful products for this job
The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.
- Cold frame: Provides a sheltered space for suitable young plants. Check anchoring, lid restraint, dimensions and glazing safety. Search Amazon for Cold frame.
- Maximum–minimum thermometer: Tracks overnight conditions around the pots. Do not treat a thermometer as frost protection; plan a suitable alternative location. Search Amazon for Maximum–minimum thermometer.
Related garden guides
- Overwintering plants in an unheated greenhouse
- Growing winter salad in a cold frame
- More greenhouse & growing guides
Sources and further guidance
- Coldframes and Mini-Greenhouses | RHS Advice
- Tender perennials: cuttings | RHS Advice
- Hardwood Cuttings | RHS Advice
Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.