Cold Frame Gardening UK: What to Grow and When to Plant
A cold frame gives seedlings and low-growing crops a sheltered place outside. Use it to harden off plants, protect hardy salads and start suitable crops when the soil is warm enough. It needs regular ventilation and can still freeze in winter. Choose the height, opening style and position around your plants, rather than expecting it to replace a heated greenhouse.
Key Takeaways
- Check temperatures before moving tender plants outside.
- Open lids or sliding panels on warm days to avoid overheating.
- Grow low crops, or choose a structure with enough mature growing height.
- Follow the fixing instructions and keep the frame level and secure.
- Use sowing dates as a starting point and adjust to local weather.
Expert Tip
Put a maximum-minimum thermometer beside the plants for a few days before moving in tender seedlings. A frame that feels warm at lunchtime may become nearly as cold as the garden overnight.
What is a cold frame?
A cold frame is a low growing structure with transparent glazing and an opening top or sliding panels. It shelters plants from wind and rain and captures solar warmth. It normally has no heating.
That makes it useful for acclimatising young plants, protecting hardy winter crops and keeping seedlings sheltered. It does not make every seed suitable for winter sowing or turn a tender plant into a hardy one.
A mini greenhouse has more vertical room, often with shelves. A full greenhouse lets you work inside and grow tall crops. Our mini-greenhouse guide covers the taller options.
What can you grow in a cold frame month by month?
Choose crops for the season and check the seed packet's sowing temperature. The calendar below is a starting point for UK gardens. Exposed, northern or higher sites may need later sowing and planting.
| Season | Useful jobs | Watch for |
|---|---|---|
| January–February | Protect established hardy salads; check overwintered plants | Cold compost and slow growth |
| March–April | Sow suitable hardy salads and raise hardy seedlings | Sunny-day overheating and late frosts |
| May | Harden off tender plants when conditions suit them | Chilly nights; bring plants back under protection if needed |
| June–August | Raise replacement salads; open or remove covers where safe | Heat, drying compost and slugs |
| September–October | Establish winter salads from suitable varieties | Declining light and damp foliage |
| November–December | Harvest established hardy leaves and inspect plants | Standing water and frost |
For more sowing options, use our month-by-month seed guide. Warmth-loving crops such as peppers need protected propagation before a cold frame becomes suitable.
How do you harden off plants in a cold frame?
Harden plants off gradually, usually over one to two weeks, as local conditions allow. Start with short periods of ventilation during mild days. Increase exposure before leaving suitable plants out overnight.
Check the forecast and the crop's temperature needs. Bring tender plants back into warmer protection when cold threatens. Leaving a lid closed all day does not prepare a plant for wind and cooler outdoor conditions.
Water as needed and check for slugs beneath pots. Keep labels with the plants so you can follow different planting dates.
Cold frame or greenhouse: which do you need?
A cold frame can be enough for salads, seedlings and seasonal protection. Choose a greenhouse when you want standing headroom, taller crops or more control over winter temperature.
They also work together. A frame can free greenhouse bench space while young plants adjust to outdoor conditions. Our unheated-greenhouse growing guide explains the wider seasonal possibilities.
Which cold frame suits your garden?
Compare access before buying. Check how far you can reach, where the lid opens and whether you need to lift heavy panels. Raised designs reduce bending, but confirm the user's reach and knee clearance rather than assuming every raised frame suits every wheelchair.
Elite Min E Lite 4x2 Cold Frame costs £249. It is a compact option; check the listed footprint and opening arrangement against the space available.
4x4 Access Aluminium Coldframe - Toughened Glass costs £427. Sliding panels give a different access arrangement from a hinged lid. Read the instructions for panel handling and securing the frame.
Palram Canopia Plant Inn 4x4 Raised Cold Frame costs £344. Its raised planting area may suit gardeners who prefer less bending. Check access and drainage before deciding.
Our cold-frame collection gives current dimensions, prices and warranty details. Compare the actual models rather than assuming every frame shares the same fittings.
Where should you put a cold frame?
Choose a bright, sheltered, accessible position with a level surface and good drainage. A sunny wall can be helpful, but avoid a spot that receives little winter light or intense reflected heat without ventilation.
Follow the manufacturer's base and anchoring requirements. Do not rely on the weight of glass alone to secure it. Keep lids clear of paths, and avoid places where falling branches or kicked balls are likely.
For balconies and shared gardens, check permission, loading and safe wind exposure before installing any structure. A small footprint does not settle those questions.
How do you stop a cold frame overheating?
Open or slide the panels as the inside warms, following the frame's instructions. Use a purpose-made stay where supplied. Do not rely on a loose stick or brick that could slip and let a glazed lid fall.
Check the thermometer after adjusting the opening. Close or reduce it when cold, rain or wind requires. An automatic opener may help on compatible hinged designs, but it will not fit every frame or operate sliding panels.
Matt's Tip: Make checking easy
Put the frame somewhere you pass each morning. Easy access makes it more likely you will open it before work, check moisture and close it when needed. A hidden corner can be inconvenient even when the frame fits neatly.
What goes wrong in winter?
Cold wet compost and stale damp air can cause trouble. Water according to the plants and compost, rather than a fixed daily routine. Empty unwanted standing water and remove dead leaves.
Hardy salads may survive frost yet grow very slowly in short days. Tender plants may need warmer shelter. Fleece can provide extra protection, but neither fleece nor a few bricks gives a guaranteed frost-proof temperature.
Frequently asked questions
Will a cold frame protect plants from every frost?
No, an unheated cold frame can still freeze. Choose hardy crops for winter and provide suitable extra protection or warmer shelter for tender plants.
Can I sow tomatoes in a cold frame in February?
A cold frame alone usually cannot provide reliable germination warmth then. Start warmth-loving crops in suitable indoor conditions and move them when local temperatures allow.
Can I use a cold frame instead of a greenhouse?
Yes, for suitable low crops, seedlings and seasonal protection. Taller crops and heated winter growing usually need a different structure. Check mature plant height before buying.
How do I stop a cold frame overheating?
Open or slide the glazing as inside temperatures rise. Use secure, compatible stays and check the thermometer. Follow the model’s instructions before fitting an automatic opener.
Does a cold frame need anchoring?
Follow the fixing instructions for the particular model and surface. A low profile or heavy glass does not remove the need to assess wind exposure and secure installation.
How long does hardening off take?
Usually one to two weeks, adjusted to the plants and weather. Increase exposure gradually and return tender plants to warmer protection if cold conditions threaten.
Related articles
- raising seeds
- what to grow in an unheated greenhouse
- hardening-off season
- essential greenhouse growing tips for beginners
- lean-to greenhouses
