Every October, I watch fellow gardeners empty their greenhouses, sweep them out, and shut the door until March. And every October, I think they’re missing the best-kept secret in gardening. Figuring out what to grow in a greenhouse in winter transformed my coldest months — instead of staring at an empty glass box all winter, I harvest fresh salad leaves on Christmas week. You don’t need a heated palace or grow lights worth a fortune. You just need the right crops and a few adjustments. For more seasonal growing advice, see the RHS guidance on winter growing.
Grow in a Greenhouse in Winter: Table of Contents
Can You Really Grow Food in Winter? Heated vs Unheated
Let’s set expectations honestly, because this is where most winter-growing advice goes wrong. A winter greenhouse is not a summer greenhouse. Growth slows dramatically — what takes 30 days in May takes 60 in January. You’re not going to harvest beefsteak tomatoes in February (unless you heat seriously and light supplementally, which costs real money).
But an unheated greenhouse typically stays 3–8°C warmer than outside, which is the difference between “everything dead” and “salad all winter” in most temperate climates. Cold-hardy crops don’t just survive in those conditions — many taste better after frost, as the cold converts starches to sugars. Kale harvested after a frost is noticeably sweeter than autumn kale. That’s not folklore; it’s plant chemistry.
If you do heat — even just keeping the greenhouse frost-free above 2–4°C — your options expand significantly. My guide on heating a greenhouse in winter covers the practical methods, from bubble-wrap insulation to small electric heaters. But everything below grows in an UNHEATED greenhouse, which is the point: winter growing is for everyone, not just those with heated setups.
1–3. Winter Salad Leaves: Lettuce, Mache and Claytonia
Salad leaves are the undisputed champions of winter greenhouse growing. They’re fast, they’re cold-tolerant, and nothing beats cutting fresh leaves in January.
Winter lettuce — choose varieties bred for cold, like ‘Winter Density’, ‘Arctic King’, or ‘Valdor’. Sow in September/October directly into greenhouse borders or trays, and you’ll be cutting leaves from November through March. Pick outer leaves and let the heart keep growing (cut-and-come-again), and a small sowing feeds you for months.
Mache (corn salad) is my personal favourite winter green. It’s absurdly hardy — shrugs off freezes that kill lesser plants — and has a lovely nutty flavour. Sow in autumn, thin lightly, and harvest rosettes through winter. It practically grows itself.
Claytonia (miner’s lettuce) is the indestructible one. It tolerates deep shade, poor soil, and serious cold. The small round leaves are mild and pleasant. Sow once in autumn and it self-seeds gently, giving you volunteers for years.
4–5. Spinach and Swiss Chard
Spinach is the king of winter greens for good reason. True spinach (not perpetual/New Zealand spinach) loves cool weather and grows steadily through winter in a greenhouse. Sow ‘Giant Winter’ or similar hardy varieties in September/October. Pick outer leaves regularly and plants keep producing. One caveat: spinach bolts at the first hint of spring warmth, so harvest hard before March.
Swiss chard (including rainbow chard) is the marathon runner — less productive in deep winter than spinach, but it keeps going where spinach gives up in spring. The colourful stems brighten the dullest January day, and both leaves and stems are edible. Plants sown in late summer will crop lightly through winter and then explode in spring.
6. Kale — The Frost-Proof Staple
Kale laughs at winter. Curly kale, cavolo nero, and Russian red kale all survive hard freezes in an unheated greenhouse and keep producing leaves. Sow in summer for winter harvests, or sow in early autumn for smaller plants that still crop.
The flavour point bears repeating: kale harvested after frost is sweeter and less bitter than pre-frost kale. I deliberately leave my best kale plants for December/January picking. Strip lower leaves as you harvest to keep air circulating, and remove any yellowing foliage promptly.
7–8. Radishes and Spring Onions: The Quick Wins
When everything else grows slowly, radishes are your morale crop. Winter varieties like ‘Black Spanish Round’ or ‘China Rose’ are hardier than summer types, and even standard radishes germinate in cool greenhouse soil. Sow every few weeks from September for a continuous supply — they go from seed to harvest in 6–10 weeks even in winter.
Spring onions (scallions) are equally obliging. Sow hardy varieties like ‘White Lisbon’ in autumn; they sit quietly through the coldest months and then surge in late winter. I use them as gap-fillers between slower crops — they take almost no space and there’s always a use for them in the kitchen.
9–10. Carrots and Beetroot
Root vegetables work beautifully in a greenhouse over winter, with one condition: deep enough soil. If your greenhouse has borders (soil beds), you’re set. In pots, use deep containers.
Carrots sown in late summer/early autumn grow slowly through winter and give you sweet, crisp roots from late winter into spring. Autumn-sown carrots are noticeably sweeter than summer ones — again, that cold-sweetening effect. Varieties like ‘Autumn King’ are bred for exactly this.
Beetroot is similarly reliable. Sow in late summer, thin to 10cm spacing, and harvest roots through winter. You can also harvest the young leaves as salad greens — a double crop from one sowing. ‘Boltardy’ is the classic reliable variety.
11. Hardy Herbs: Parsley, Chives and Coriander
Fresh herbs in winter feel like luxury, and they’re easy. Flat-leaf parsley sown in summer keeps producing in an unheated greenhouse all winter — it’s biennial, so one sowing gives you two years. Chives die back but their roots survive; pot up a clump in autumn and it regrows slowly through winter. Coriander is trickier (it bolts easily) but autumn-sown plants in a cool greenhouse grow slowly without bolting, giving you winter leaves.
Mint in a pot (always a pot — never plant mint in greenhouse soil unless you want a mint greenhouse) keeps ticking over and regrows from the roots. Between parsley, chives, and mint, your winter cooking is covered.
12. Microgreens: The 2-Week Crop
When you want results NOW, microgreens are unbeatable. Radish, mustard, cress, and pea shoots go from seed to harvest in 7–14 days on a greenhouse shelf — no special equipment, just trays, compost, and water. They don’t care about short days or cool temperatures the way mature plants do.
I keep a constant rotation of two trays through winter. They’re the most productive square foot in my greenhouse from November to February, and pea shoots in a winter salad are genuinely delicious.
What NOT to Grow in a Greenhouse in Winter
Just as important as what to plant: what to skip. Don’t waste space and hope on tomatoes, cucumbers, peppers, aubergines, or melons in an unheated winter greenhouse — they need warmth and long days that winter can’t provide. They’ll sit stunted, catch disease, and disappoint you.
Also skip anything that needs pollinators to fruit (no bees in January) and anything marginal for your climate that you’d have to heat expensively. Winter growing works because you match crops to conditions, not because you fight the season.
5 Tips for Winter Greenhouse Success
1. Maximise light. Wash the glass (autumn is the perfect time), remove shading, and keep the interior as bright as possible. Light is the limiting factor in winter, more than temperature.
2. Water sparingly, in the morning. Plants barely drink in winter. Overwatering in cold, still air causes more winter losses than cold itself. Water only when the soil is dry a couple of centimetres down, always in the morning so surfaces dry by night.
3. Ventilate on mild days. It feels wrong to open vents in winter, but stagnant humid air breeds grey mould. Open up briefly on mild, dry days to exchange the air. A small circulating fan on cold days also helps enormously.
4. Insulate simply. Bubble wrap on the inside of the glass (the large-bubble horticultural kind) adds a few precious degrees on cold nights. It’s cheap, reusable, and makes a measurable difference.
5. Watch for pests. Aphids and grey mould love the mild, still conditions of a winter greenhouse. Check plants weekly, remove dead leaves promptly, and deal with aphids early — they multiply fast even in cool weather.
Frequently Asked Questions
What is the easiest thing to grow in a greenhouse in winter?
Winter salad leaves — lettuce, mache, and claytonia. They’re the most forgiving: sow in autumn, harvest through winter, and they tolerate the cold, low light, and beginner mistakes better than anything else. If you grow only one thing this winter, make it salad leaves.
Do I need to heat my greenhouse to grow in winter?
No — all the crops in this guide grow in an unheated greenhouse in temperate climates. Heating (even just frost-free) expands your options and speeds growth, but it’s optional, not required. An unheated greenhouse typically stays several degrees warmer than outside, which is enough for cold-hardy crops.
When should I sow winter greenhouse crops?
Most winter crops are sown in late summer to early autumn (August–October), so they’re established before the darkest months. Salad leaves and radishes can be sown into October; kale, spinach, and carrots do best sown in August–September. Microgreens can be sown any time.
Why is everything growing so slowly in my winter greenhouse?
That’s normal — short days and cool temperatures slow all growth dramatically. A crop that takes 30 days in spring takes 60+ in midwinter. Plan for it: sow earlier, sow more, and harvest patiently. Growth accelerates rapidly from late February as days lengthen.
Can I grow tomatoes in my greenhouse over winter?
Not in an unheated greenhouse — tomatoes need warmth (minimum ~12°C at night) and long daylight hours that winter doesn’t provide. They’ll sit stunted and catch disease. Save your space for cold-hardy crops, and start tomato seeds in late winter for the spring season instead.
Final Thoughts
The question of what to grow in a greenhouse in winter has a better answer than most gardeners expect: plenty. Salad leaves on Christmas Day, sweet frost-kissed kale in January, radishes in February, and microgreens all along — none of it needs heating, grow lights, or expertise. Just the right crops, sown at the right time, with a little winter wisdom.
This October, don’t shut the greenhouse door. Sow some winter lettuce, tuck in a row of radishes, and see for yourself. Winter might become your favourite growing season.
