What to Grow in a Greenhouse: The Plants Worth the Space

Which vegetables do best in a greenhouse?

What these crops have in common is that they originate in warmer climates than most of us garden in, and want steadier heat, less wind and a longer season than an open plot can offer. A greenhouse gives them all three at once, which is why the difference in harvest is so noticeable.

Tomatoes

Tomatoes are the classic greenhouse crop for good reason. The plant wants steady warmth, dry foliage and at least 12–14 hours of light during peak season to set fruit reliably. Under cover, the first ripe tomato often arrives two to three weeks earlier than outdoors, and the season keeps producing well into early autumn. See our full guide on how to grow tomatoes from seed to harvest.

Cucumbers

Cucumbers are at least as heat-dependent as tomatoes, but also want higher humidity — a combination that's hard to achieve outdoors in a cool, temperate climate but comes naturally in an enclosed greenhouse. Nights below 10°C (50°F) slow growth noticeably, which is exactly the gap a greenhouse closes. Our guide on how to grow cucumbers covers varieties and care in more detail.

Chillies and peppers

Both want a long, warm season to set fruit that actually ripens before the weather turns. Outdoors in most temperate climates, sweet peppers often stay green all season, while the extra heat and wind shelter of a greenhouse lets them turn red, yellow or orange. Chillies are usually even more dependent on that extra warmth than sweet peppers. Our guide on how to grow chillies breaks varieties down by how much season they need.

Aubergines (eggplants)

Aubergine is one of the most heat-demanding vegetables you can grow under cover. It wants consistent warmth day and night and drops flowers readily if temperatures sit below 15°C (59°F) for any length of time. Without a greenhouse, it's a genuinely difficult crop to bring to harvest in a cooler climate, and a marginal one even where summers run warm.

Melons

Melons need more heat, space and patience than most home growers expect, but in a well-run greenhouse, smaller varieties like cantaloupe or honeydew types are genuinely achievable. The plant sprawls across a lot of floor space unless trained vertically, so budget for it competing with everything else you'd like to grow. Watermelon is even more demanding on heat and time than cantaloupe, and usually only succeeds in a greenhouse with long, steady summer warmth — in a cooler or shorter season, you're more likely to end up with a large plant and small, half-ripe fruit.

Worth knowing. Choose determinate (bush-type) tomato varieties, or ones bred specifically for greenhouse growing, if space is tight. Indeterminate varieties can reach several metres in a single season and need repeated pruning of side-shoots, which matters when you're already working out how to size a greenhouse for what you want to grow.

Fruit you can grow under cover

Fruit rarely tops the list when people plan a greenhouse, but several kinds genuinely do better indoors than out — especially anything sensitive to rain, cold or a short growing window.

Strawberries in pots or grow-bags crop earlier and more reliably under cover, since the flowers escape late frost damage and pollinators find them more easily in still air (though you sometimes need to hand-pollinate — more on that below). See our guide to growing strawberries. Grapes ripen far more reliably in a greenhouse than outdoors across most temperate climates, since they want long, dry warmth that outdoor summers don't always deliver. Citrus trees in pots — lemon, lime, calamondin — can spend summer in a cooler conservatory or greenhouse for fragrance and fruit, but need moving to a cool, bright winter spot once temperatures drop close to freezing.

Figs and peaches — bigger fruiting plants under cover

Figs are surprisingly achievable in a cooler climate if given some shelter, but rarely produce more than one crop outdoors where summers run short. Under cover — planted in the border or in a large pot of at least 40–50 litres — figs ripen far more reliably. Prune hard every spring; left unchecked, a fig quickly outgrows most greenhouses.

Peaches and nectarines are usually grown as fan-trained trees against a wall or gable inside the greenhouse. The main advantage isn't just warmth — it's that early spring blossom is protected from the frost that would otherwise wipe out the whole year's crop. Because that blossom opens before outdoor pollinators are active, you'll usually need to hand-pollinate with a soft brush, much like early strawberries in a closed greenhouse.

Herbs worth growing in a greenhouse

Most herbs are perfectly happy outdoors, but a few of the most commonly grown ones genuinely belong under cover — particularly the ones sensitive to cold or that want steadier moisture than an average summer provides.

Basil is the clearest case. It sulks and drops leaves at even a brief dip toward 10°C (50°F), which makes it hard to keep productive outdoors for more than a few weeks in a cooler climate. Under cover, you can harvest from early summer well into autumn. Coriander bolts quickly in heat but still appreciates the wind shelter a greenhouse gives early in the season. Lemongrass and Thai basil are examples of tropical herbs that essentially need greenhouse or indoor conditions to crop well outside the tropics.

Parsley, chives, tarragon, thyme and rosemary, on the other hand, do fine outdoors or in a pot on a sheltered patio and don't need to take up valuable greenhouse space. For a broader look at what suits where, see our guide to growing herbs.

Flowers and houseplants in the greenhouse

A greenhouse doesn't have to be all edibles. Several flowers and houseplants do better for the wind shelter, warmth and steadier humidity a greenhouse provides, particularly early and late in the season.

Pelargoniums and petunias can be started earlier under cover than a windowsill allows, then moved outside once nights are reliably warm. Fuchsias and begonias enjoy the bright but indirect light a partly shaded greenhouse offers in summer. Orchids and other tropical houseplants that normally live indoors can move to a shaded corner of the greenhouse for summer, where the higher humidity suits them better than a typical dry indoor room.

Many gardeners also use the greenhouse to start summer bedding and vegetable seedlings earlier than a windowsill allows — see our seed sowing calendar for timing by crop.

Worth knowing. Don't let houseplants crowd out the vegetables if you're growing for harvest. Ornamentals take up bench space and shade that would otherwise go to crops that actually need every sunny hour you can give them.

What should you NOT grow in a greenhouse?

Greenhouse space is the most expensive square metre in the garden, once you count materials, any heating, and the time it takes to manage. Some plants give back so little for that space that they're rarely worth prioritising there.

Common mistake. Growing cold-hardy crops under cover just because there's spare space, rather than because they need it. That space is worth more given to a second round of lettuce, a third chilli plant, or extra basil — crops that actually use what a greenhouse offers that the open garden can't.

A closed, humid greenhouse also raises the risk of fungal problems like grey mould and blight if the air sits still for too long. Potatoes and tomatoes share several diseases, including late blight, so growing them in the same space increases infection risk rather than saving room. More on avoiding that in the crop rotation section below.

What to grow early and late in the season?

A greenhouse works hardest when it isn't standing empty between starting tomatoes in spring and pulling them out in autumn. Fast-growing, cold-tolerant crops can fill both gaps.

Early in spring, before nights are warm enough for tomatoes and cucumbers, lettuce, spinach, radishes, chard and baby leaf mixes do very well. They germinate at lower temperatures, grow quickly, and are ready to harvest in four to six weeks — well before the greenhouse is really needed for heat-loving crops. In autumn, once tomato plants come out in September or October, the same fast crops can be sown again for a final harvest before winter, often weeks later than would be possible outdoors.

Want to start the season even earlier, whatever your zone? Starting seeds indoors under grow lights is usually what decides whether you get a full harvest before autumn arrives. See our guides on starting seeds indoors and grow lights for seedlings.

Another way to make the most of the season is to sow in succession rather than all at once. Sow a short row of lettuce or radishes every two to three weeks from when the greenhouse frees up in spring, instead of one large sowing. That gives a steady trickle of harvest over several months rather than a glut followed by empty benches, and you avoid a surplus that bolts before you can eat it.

How to combine plants without them competing

A small greenhouse rarely has room for everything you'd like to grow at once, and some combinations work better than others in practice.

Tomatoes and cucumbers tolerate the same temperature but don't love sharing a watering schedule — cucumbers want steadier, higher humidity, while tomatoes do best when the compost dries slightly between waterings to avoid split fruit. Growing them side by side means compromising, or watering them separately in different parts of the greenhouse. Chillies and aubergines share similar needs for heat and drier air, and usually get along well together.

Pollination is another factor. Tomatoes, chillies, peppers and aubergines are self-pollinating and usually manage fine on their own if you tap the flower trusses gently to spread pollen, especially in a closed greenhouse with few insects. Cucumbers and melons, on the other hand, often need help from pollinating insects or hand-pollination if doors and vents stay shut during flowering — otherwise they can flower heavily without ever setting fruit.

Tall climbers like cucumbers and indeterminate tomatoes should sit at the back or against a gable end so they don't shade lower-growing plants like lettuce, strawberries or herbs during the morning. If you want to combine crops more deliberately, the same principles behind outdoor companion planting apply under cover too, just on a smaller scale.

Scent can play a role as well. Many experienced growers plant basil near tomatoes in the belief that it deters certain aphids, though the effect is hard to measure scientifically. What's more certain is that strongly scented herbs like mint spread aggressively by runners if planted straight into a greenhouse bed — keep it in its own pot instead of letting it compete for root space with its neighbours.

Worth knowing. Position the most heat-demanding plants — aubergine, chilli, melon — furthest from the door where temperature stays most even, and put cold-tolerant crops like lettuce and strawberries nearest the entrance, where it's coolest.

Choosing greenhouse crops, step by step

1. Start with what has no real outdoor alternative. Tomatoes, cucumbers, chillies, peppers and aubergines usually top this list in a temperate climate.
2. Think in square metres, not plant count. One indeterminate tomato and one climbing cucumber together take up nearly as much floor space as four or five compact potted chillies.
3. Fill the edges with fast crops. Lettuce, radishes and baby leaf grow quickly and can be tucked around the larger crops without seriously competing for light.
4. Plan for spring and autumn, not just summer. Decide now what will replace the tomatoes once they come out in early autumn, so the bench doesn't sit empty.
5. Group plants by water needs. Put plants with similar moisture and temperature requirements near each other so you're not compromising on watering.
6. Keep space-hungry crops outside. Potatoes, sweetcorn, pumpkins and similar crops belong in the open garden — leave them there.

Do you still need crop rotation under cover?

Yes, more than most people expect. A greenhouse often keeps the same soil year after year, unlike an outdoor plot where it's easier to move crops between beds. That means diseases and pests that thrive in warmth and still air — root-knot nematodes and tomato wilt, for example — can build up in the soil considerably faster than outdoors.

Avoid growing tomatoes, chillies, peppers or aubergines in exactly the same spot several years running. Replace the top 15–20 cm (6–8 in) of soil every three years if you grow directly in a greenhouse bed, or grow in large pots and grow-bags that you empty and refill with fresh compost each season. The general principles behind crop rotation still apply under cover, just at a smaller scale and under more pressure, since the space is so limited.

Common mistake. Assuming greenhouse soil never needs replacing because it still looks fine on the surface. Soil-borne disease problems rarely show up until the harvest is already affected — often by year three or four in the same soil.

Common mistakes when choosing greenhouse plants

• Growing everything you have seed for. Greenhouse space is limited — prioritise what genuinely needs the heat, not whatever's left in the seed drawer.
• Forgetting the shoulder seasons. Growing only tomatoes and cucumbers and leaving the greenhouse empty in April or October wastes half its value.
• Mixing incompatible water needs. Putting a cactus, a tomato and a lettuce on the same watering routine eventually shortchanges one of them.
• Growing disease-prone crops in the same soil every year. Without rotation, soil-borne problems build up faster under cover than outdoors.
• Underestimating pollination needs. Cucumbers and melons in a closed greenhouse with no insects can flower heavily without setting a single fruit.
• Letting tall climbers shade everything else. Position them against the gable end, not in the middle where they block the best light from lower crops.

Frequently asked questions

What's best to grow in a small 6 m² (65 sq ft) greenhouse?
Prioritise what gives the most return per square metre: tomatoes, cucumbers and chillies in pots or a bed, filled in with fast-growing lettuce and radishes around the edges in spring and autumn. Skip space-hungry crops like pumpkins, sweetcorn and potatoes that do just as well outdoors.

Can you grow vegetables in a greenhouse all year round?
Yes, but it usually requires supplemental heat and often grow lights during the darkest months, especially in colder zones. Without a heat source, most greenhouses realistically deliver an extended season from early spring to late autumn rather than continuous winter cropping.

Which vegetables do NOT belong in a greenhouse?
Potatoes, sweetcorn, pumpkins, squash and Jerusalem artichokes take up a lot of space for a long time without gaining much from the greenhouse climate. They do just as well, or better, outdoors, and occupy room that could otherwise go to heat-loving crops that actually need it.

Can tomatoes and cucumbers share the same greenhouse?
Yes, they tolerate the same temperature range, but prefer slightly different humidity — cucumbers want it steadier and higher, tomatoes a touch drier between waterings to avoid split fruit. Place them in different parts of the greenhouse if you can, or accept a compromise between their ideal watering schedules.

Do I need to hand-pollinate greenhouse vegetables?
Tomatoes, chillies, peppers and aubergines are self-pollinating and usually manage on their own, especially if you tap the flower trusses gently. Cucumbers and melons often need help from insects or hand-pollination if doors and vents stay closed during flowering.

Do herbs like basil do better in a greenhouse than outdoors?
Yes, particularly basil, coriander and tropical herbs like lemongrass. They're sensitive to cold and crop more evenly and for longer under a greenhouse's sheltered climate than on a windy outdoor patio.

Can I grow flowers in the same greenhouse as vegetables?
Yes, but give vegetables priority on the sunniest bench space if room is limited. Flowers like pelargoniums and petunias can be started early in the greenhouse and then moved outside, rather than occupying bench space all summer.

How often should I rotate crops in a greenhouse?
Avoid growing the same plant family, such as tomatoes and aubergines, in exactly the same spot more than two years running. Replace the top 15–20 cm (6–8 in) of soil every three years if growing directly in a bed, or use pots and grow-bags refreshed with new compost each season.

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