A cold frame or a greenhouse – which is the best option for your garden? Whether you are just starting out or looking to extend your growing season, both offer real benefits. This guide takes you through the key differences, explains how to get the most from a cold frame, and helps you decide which is right for your space and ambitions.
What Is a Cold Frame?
A cold frame is a small, enclosed structure that helps gardeners extend the growing season by protecting plants from cold, wind and frost. It is usually a box-shaped frame with a transparent lid made from glass or polycarbonate that lets in sunlight while trapping heat inside.
Cold frames create a sheltered microclimate at ground level, perfect for raising plants from seed and hardening off young plants before moving them into the garden. They also provide valuable protection for delicate plants during autumn and winter.
Cold Frame vs Greenhouse: At a Glance
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Feature |
Cold Frame |
Greenhouse |
|
Size |
Compact (e.g. 2.5 x 3 ft) |
From 6x4 ft to 20x20 ft |
|
Design |
Box with a transparent lid |
Full structure with walls and roof |
|
Climate Control |
Natural heat and sunlight only |
Vents, heating, shading, irrigation |
|
Best For |
Hardening off, early starts, overwintering hardy plants |
Year-round growing, wide range of crops |
|
Flexibility |
Portable, easy to move |
Permanent garden feature |
|
Cost |
Affordable, compact entry point |
Bigger investment, more space needed |
|
Longevity |
Durable, ideal for seasonal use |
Built for year-round use, 25-year guarantees |
The Key Differences Explained
Maintenance and Durability
Cold frames are low-maintenance, usually needing little more than an occasional clean. Quality models use aluminium and toughened safety glass to withstand the elements. Greenhouses involve more upkeep, from checking glazing and vents to keeping gutters clear, but they are designed as permanent features that stand the test of time.
Growing Conditions
Cold frames create a cosy microclimate at ground level that is perfect for nurturing seedlings and hardening plants. A greenhouse allows for full climate control with features like automatic roof vents, side louvres and heating systems. This makes it possible to grow salad leaves in winter, tomatoes in summer, and a wide variety of plants all year. For tips on managing heat, see our guide on keeping your greenhouse cool in summer.
Mobility vs Permanence
Cold frames are portable and can be repositioned in the garden to catch the best light. Greenhouses are permanent structures that become part of your garden design, and can also add to your property’s appeal.
Cost Over Time
Cold frames are an affordable entry point, ideal for beginners or smaller gardens. Greenhouses are a bigger upfront investment, but with their longevity and guarantees of 25 years or more, they offer excellent value in the long run. If you are weighing up your options, our guide on things to know before buying a greenhouse is a good place to start.
Security and Protection
Cold frames protect plants from frost and sudden temperature drops at ground level. Greenhouses provide an even more secure environment, fully enclosing your plants against harsh weather, pests and wildlife. For more on keeping your greenhouse pest-free, see our dedicated guide.
How to Transition Plants from Cold Frame to Garden
Moving plants from the shelter of a cold frame to the open garden is a crucial step. Get it right, and your plants will thrive. Rush it, and they can suffer transplant shock.
Acclimation
Acclimation helps transition your plants from one environment to another. Start by opening the lid of your cold frame for a few hours during the day, introducing your plants to the range of temperatures and weather conditions in your garden. Begin with short periods and build up gradually.
Hardening Off
Following acclimation, hardening off takes it a step further. Remove your plants from the cold frame and introduce them to the outdoors. Over a period of one to two weeks, gradually increase the time they spend outside, starting with an hour and building up. Take things slowly to reduce the risk of shock.
Signs Your Plants Are Ready
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Root check: If the roots are well developed but not overcrowded, your plant is likely ready for the move.
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Growth spurt: Strong stems and healthy leaves above the soil are a good sign that the plant is ready to go.
Tips for a Smooth Transition
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Avoid transplanting during the hottest part of the day. Early morning or late afternoon is gentler on your plants.
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Check thoroughly for pests and diseases before transplanting to avoid spreading problems to your garden.
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Plant at the correct depth and give each plant enough space. Too deep or too close together can hinder growth.
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Keep an eye on nighttime temperatures. If it gets too cold, bring plants back under cover or protect them with fleece.
Companion Planting in Cold Frames
Companion planting in a cold frame goes beyond saving space. Strategic pairing of crops can enhance plant health and deter pests, creating a balanced ecosystem in a small footprint.
Great Pairings for Cold Frames
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Carrots and radishes: Quick-sprouting radishes serve as a natural pest deterrent for carrots.
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Lettuce and aromatic herbs: Basil or coriander planted alongside lettuce maximises space and uses the herbs’ scent to repel pests.
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Spinach and strawberries: Spinach thrives in the partial shade provided by strawberry plants.
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Kale and herbs (thyme or chives): Strong-scented herbs help deter pests from kale.
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Beetroot and garlic: Garlic planted near beetroot can help deter pests and improve flavour.
Succession Planting in Cold Frames
Succession planting transforms your cold frame into a year-round source of produce. By staggering your sowings, you ensure a steady harvest rather than a single glut.
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Stagger your seeds: Sow every two to three weeks for a continuous supply rather than one big harvest.
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Rotate by season: When one crop is done, replace it with something suited to the next phase of the year.
Good Combinations for Succession Planting
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Leafy greens: Start lettuce, spinach and kale early and resow every few weeks. As the weather warms, switch to shade-tolerant varieties.
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Radishes then carrots: Radishes mature quickly. As you harvest them, carrots continue growing in the freed-up space.
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Swiss chard then beans: After harvesting early chard, plant beans in the same spot. The beans add nitrogen to the soil, benefiting the next crop.
What Else Can You Grow in a Cold Frame?
Salads
Rocket lettuce thrives in the cool, controlled environment of a cold frame, maturing quickly for a fast harvest. Green onions are hardy and easy to grow, providing flavour throughout the season.
Root Vegetables
Turnips grow well in cooler temperatures, perfect for early spring or late autumn planting. Parsnips have a sweet, nutty flavour that intensifies in the cold, making them an excellent choice for a longer growing season.
Flowers
Pansies and violas are cold-tolerant and add colour in early spring or late autumn. Primroses thrive in cool conditions and offer a burst of colour in late winter. Snapdragons can be started in a cold frame for an extended blooming period, while sweet peas benefit from the early protection to produce beautifully fragrant, earlier blooms.
Is There Something in Between?
Yes. A patio greenhouse bridges the gap. Larger than a cold frame but more compact than a full greenhouse, it is a great solution for gardeners with limited space who still want the benefits of a true greenhouse environment. It is ideal for balconies, small gardens or courtyards. For help deciding on size, see our guide on how to choose the right size greenhouse.
