A polytunnel is a season-extender that allows us to grow vegetables not just in summer, but through autumn and even through the winter months. Knowing which vegetables to grow in autumn helps you to keep your polytunnel full and productive all year round.
Autumn is often seen as the time when gardens wind down – when harvest baskets overflow and beds are cleared in readiness for winter. But for those with a polytunnel, autumn can be a season of renewal and opportunity rather than decline.
By using the protection of a polytunnel, you can continue sowing, planting, and harvesting far beyond what’s possible outdoors. Whether you want to grow fresh produce for autumn meals, start crops for winter and spring, or plant perennial vegetables that will reward you year after year, a polytunnel opens up a wealth of possibilities.
Understanding what vegetables to grow in autumn and, just as importantly, what not to grow, is the first step toward extending your harvest season and keeping your garden productive all year long.
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KEY TAKEAWAYS
- A polytunnel allows you to grow vegetables well into autumn and even through winter in the UK.
- Some crops should be sown earlier in spring or summer to provide abundant harvests through autumn.
- There are also fast-growing autumn vegetables that you can sow and harvest within weeks before the first frosts arrive.
- Autumn is an excellent time to sow and plant for winter or spring harvests, ensuring a seamless transition between seasons.
- Don’t forget perennial vegetables – planting these in autumn can establish strong root systems before spring.
- Managing light, ventilation, and soil fertility in your polytunnel is crucial for successful autumn growing.
Understanding What Vegetables to Grow in Autumn and What Not to Grow
The cooler, shorter days of autumn change how plants behave. Growth slows as daylight diminishes, and soil retains more moisture. In this season, it’s important to focus on crops that either thrive in cooler conditions or that can mature before growth slows too much.
Hardy greens, root crops, and certain herbs all adapt well to the cooler weather of early autumn. However, heat-loving summer crops such as tomatoes, aubergines, and cucumbers will begin to struggle as temperatures drop and light levels fall.
If you still have summer plants in your tunnel, keep harvesting until yields naturally decline. Then, clear space for new, cool-weather crops. You’ll find that autumn-grown vegetables often develop richer flavours, firmer textures, and fewer pest problems than those grown in summer.
Avoid sowing plants that require long daylight hours or high heat such as sweetcorn, melons, or peppers, since they won’t mature properly once autumn sets in. Instead, think about continuity: which crops can replace your summer harvests and keep the garden ecosystem thriving?
Autumn Vegetables to Grow in Spring and Summer for Autumn Meals
Many of the best autumn vegetables are those that you started earlier in the year: plants that were sown in spring or summer but reach their peak harvest during the crisp, cool months of September through November.
Carrots and Beetroot
Root crops sown in late spring or early summer are ideal for autumn meals. Carrots and beetroot mature beautifully under a polytunnel’s gentle protection, and their flavour actually improves with cooler nights. The reduced risk of carrot fly in autumn makes this an especially good time to enjoy these earthy favourites.
Cabbages and Kale
Brassicas planted in summer continue to provide food deep into autumn. Varieties like ‘January King’ cabbage and ‘Cavolo Nero’ kale grow steadily and benefit from the extra warmth of a polytunnel. These plants also withstand light frosts, so you can harvest over an extended period.
Leeks and Celery
Leeks sown in spring mature slowly, ready for harvesting through autumn and early winter. In a tunnel, they’re protected from harsh winds and heavy rain, resulting in tender, straight stems.
Celery, too, appreciates the stable moisture levels inside a polytunnel, producing crisp stalks long after outdoor crops have ended.
Pumpkins and Squash
While pumpkins and squash are warm-weather crops, autumn is their time to shine. If you started them early in the summer, they’ll ripen through September and October. Curing them under cover in the polytunnel ensures excellent storage quality – ideal for soups and roasts through the colder months.
These crops show how thoughtful spring and summer planning leads to autumn abundance.
Fast Growing Autumn Vegetables to Sow and Harvest in Autumn
Even as days shorten, you can still sow and harvest quick-maturing vegetables that thrive in cooler conditions. The trick is to choose fast growers and make the most of the mild microclimate within your polytunnel.
Radishes
Radishes are the quintessential fast crop, ready to harvest in just 3–4 weeks. Sow small amounts every couple of weeks from August through October for a steady supply. Varieties like ‘French Breakfast’ or ‘Sparkler’ perform particularly well under cover.
Spinach and Oriental Greens
Spinach germinates readily in the cooler soils of early autumn and grows well in lower light. Pair it with oriental greens such as mizuna, pak choi, and tatsoi – all of which mature quickly and can be harvested leaf by leaf. These crops are ideal for stir-fries and salads, offering fresh greens when many other plants are slowing down.
Lettuces and Salad Mixes
Hardy lettuces like ‘Winter Gem’ or ‘Valdor’ can be sown in early autumn for harvests through October and November. Combine them with rocket, mustard, and corn salad for mixed salads that bring colour and texture to autumn meals.
Turnips and Kohlrabi
Both turnips and kohlrabi mature in around eight weeks, making them excellent short-season choices. The mild conditions inside a polytunnel prevent them from becoming woody and allow for crisp, tender bulbs – perfect for roasting or eating raw in slaws.
Even small sowings of these quick crops help keep soil active, support beneficial soil organisms, and make the most of your space before winter sets in.
Sowing in Autumn for Winter or Spring Harvests
Autumn is not only about harvesting; it is also a time for forward planning. By sowing at this point, you can prepare your polytunnel for the months ahead, ensuring that your garden continues to provide food when little else is growing.
Garlic and Onions
Plant garlic cloves and overwintering onion sets in October or November. They will root through the winter, protected by the tunnel’s cover, and surge into growth with the first warmth of spring. Choose UK-hardy varieties such as ‘Solent Wight’ garlic and ‘Senshyu Yellow’ onion for reliable results.
Broad Beans and Peas
Sowing broad beans like ‘Aquadulce Claudia’ or hardy pea varieties such as ‘Meteor’ in late autumn gives them a head start. They establish roots before winter, overwinter as small plants, and are among the first crops to bear in early spring. Inside a polytunnel, they are shielded from frost and high winds.
Winter Salads and Greens
You can sow hardy salad greens such as claytonia (miner’s lettuce), lamb’s lettuce (corn salad), and winter purslane through September and October. These low-growing plants thrive in the lower light and cooler air of autumn and can be harvested right through winter with minimal care.
Spring Cabbage and Cauliflower
Sow spring cabbage and cauliflower seeds in August or early September, then transplant into the polytunnel in autumn. These crops will grow slowly through winter and burst into rapid growth as temperatures rise, providing early greens when they are most welcome.
Autumn sowing ensures your polytunnel never stands idle, and each bed transitions smoothly into the next phase of productivity.
Beyond Annuals – Perennial Vegetables to Plant in Autumn
While annuals dominate most kitchen gardens, autumn is also the ideal time to establish perennial vegetables. These crops return year after year with minimal effort. In permaculture, they are prized for their resilience, low maintenance, and ability to stabilise soil ecosystems.
Asparagus
Asparagus crowns planted in early autumn establish strong roots before winter and emerge vigorously in spring. A polytunnel protects young plants from excess moisture and frost, helping them settle in faster. Though you will wait a couple of years for full harvests, the reward is a long-term, sustainable crop.
Rhubarb
Rhubarb can be planted in autumn to give it time to root well before its spring surge. Inside a tunnel, the soil stays warmer, encouraging early shoots. Forcing a few crowns under cover can provide the first tender stems weeks ahead of outdoor plants.
Perennial Kales and Spinach
Perennial kales like ‘Daubenton’s Kale’ or ‘Taunton Deane’ are ideal additions to an autumn planting scheme. They produce edible leaves year-round and benefit from polytunnel protection in their first year as they establish. Likewise, perennial spinach such as Hablitzia tamnoides (Caucasian spinach) can be planted in autumn to settle in before cold weather arrives.
Welsh Onions and Chives
These hardy alliums thrive with an autumn planting. Once established, they produce year after year with minimal care. Welsh onions can be harvested like spring onions, while chives bring reliable, fragrant growth each spring.
Planting perennials in autumn is an investment in the future, creating a more self-sustaining and resilient food system within your polytunnel or elsewhere in your garden.
Tips for Growing Vegetables in a Polytunnel in Autumn
A successful autumn garden depends as much on management as on plant choice. The changing season brings cooler nights, heavier dew, and shifting light levels, all of which require small adjustments to keep your crops thriving.
First, clean and tidy your polytunnel. Remove summer plants as they finish cropping, along with any dead leaves or debris that might harbour pests or disease. Adding a fresh layer of compost to beds replenishes nutrients after a busy summer season.
Keep an eye on ventilation. While warmth is valuable, stagnant air can encourage moulds and mildew. Open vents or doors on mild days to let fresh air circulate, and close them again in the evening to retain heat.
As light levels fall, try to maximise sunlight exposure. Wash the tunnel cover to remove algae or dust that block light, and orient crops to make best use of available daylight. Shorter crops should sit on the south-facing side of the tunnel, taller ones to the north.
Water sparingly but consistently. In autumn, evaporation slows, so plants need less frequent watering. Focus on the root zone, avoid wetting foliage, and reduce humidity by watering early in the day.
Finally, consider using mulches and thermal mass such as compost, straw, or dark water containers to help regulate temperature and conserve soil moisture. These techniques create a stable environment where growth continues smoothly despite the shifting weather outside.
What is the best plant to grow in autumn?
Some of the best vegetables to grow in autumn include leafy greens such as kale, spinach, and winter lettuce, along with root crops like carrots and beetroot. Autumn is also ideal for planting garlic, onions, and broad beans for the following spring.
What vegetables do I plant in autumn?
You can plant a wide range of hardy vegetables, including spinach, mizuna, rocket, pak choi, turnips, and spring cabbage. For overwintering, choose crops like garlic, onions, and broad beans. In a polytunnel, the mild conditions allow these to thrive even when outdoor growth slows.
Can you plant vegetables in October in the UK?
Yes. October is a great time to plant hardy and overwintering crops such as garlic, onion sets, broad beans, and winter salads. In the sheltered environment of a polytunnel, you can also continue sowing fast-growing greens like rocket, mustard, and corn salad for harvest before Christmas.
Sources
Arricca Elin Sansone (2025) Put the cold-sensitive perennials down – 7 things you should never plant in autumn. Available at: https://www.countryliving.com/uk/homes-interiors/gardens/g65966227/what-not-to-plant-in-autumn/ (Accessed: 29 September 2025).
