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Polytunnels in autumn

Autumn in the polytunnel is a time for planting for the winter and hungry gap, as well as for harvesting melons and other autumnal treats. To make the most of growing under cover through winter, you should be sowing nearly as many seeds as you were in spring. It’s also time to check your cover for damage and to give it a quick clean if algae has built up in the damp weather, to let as much light as possible get in during the winter.

Planting for autumn

Tunnel winter crops need to be sown by the middle of September at the very latest. Here are some potential winter tunnel crops to consider, which are all likely to survive right through until spring: celery, chard, chicory, Chinese cabbage, carrots, cauliflowers, corn salad, beetroots, endive, lettuces (all kinds), mizuna, winter peas, parsley, autumn-sown broad beans, radishes, rocket and spinach.

melon and physalis harvest in autumn polytunnel, image

autumn treats

Planting to meet the hungry gap can also take place at this time of year, but getting the timing right is tricky; you need the plants to establish properly before the light levels drop so that they are ready to take off again in the spring, but a little too early and they will crop before you really need them.

Timing is very much dependant on your local climate and particularly the number of sunny days you receive in winter, so note down your planting dates and a few remarks about the winter weather. This will help you develop the expertise to master the trick of producing spring onions while you are waiting for early japanese onions outdoors, overwintering broad beans while your neighbours are anxiously waiting for their first plants to germinate, and armfuls of kohl rabi and baby carrots for fresh buttered vegetables… to go with your astonishingly early potatoes!

Polytunnel tasks

Inspect the entire tunnel cover, and fix anything that flaps by using repair tape on both sides of the cover. Clear away summer crops to make way for winter planting and clip up unwanted string supports with clothes pegs. As soil becomes vacant, top-dress with 7.5cm (3″) of compost. Keep the doors open all day and keep a close eye out for moulds and fungi, especially on blight-prone plants such as tomatoes – which should have their tops nipped out towards the end of September to prevent any more fruit trusses from forming. Top-dress any bare soil with compost. Bring pot-grown herbs such as basil into the tunnel to extend their season. If your local climate is too cool to do so outside, some early potatoes can be planted in soil beds or deep pots to provide a crop of new potatoes for the table at Christmas.

As temperatures fall so does the tunnel’s requirement for water, so do not forget to adjust any automatic watering systems. In any season the best time of day for watering is first thing in the morning, but this is particularly important in autumn because there is a higher risk of fungi and moulds attacking plants.


Globe artichokes (second flowering), peppers and chilli peppers (taken red), tomatoes, basil, physalis, melons, watermelons, cucumbers, courgettes, aubergines, celeriac (does well with longer growing season), celery, fennel, primocaine raspberries, monster-sized onions, French and runner beans. If the weather outside is less than ideal pumpkins should be brought in and left for 7-10 days to cure the skins; onions dry well on the staging and can be stored over the winter in strings hanging from the crop bars.

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9 Responses to “Polytunnels in autumn”

  1. Ben says:

    Is it best to harvest physalis when they are green like this?
    What do you do with them then?
    This is the first year I have grown them and they are green on the plant but I was going to wait for them to ripen.

    • Andy McKee says:

      You’ve not mentioned if you’re in a polytunnel or not, but I’m assuming so.
      Unlike the ornamental types, you don’t have to wait for the papery calyx to change colour (although it will dry to yellow eventually). Without heat physalis can be tricky to ripen in poor summers like this one, even in a polytunnel: so get them started really early, leave them in as late as possible (frost will kill them), and hope for sun.
      Now the good news – unless you get really low temps in winter you can overwinter the plants in your tunnel, and they’ll be earlier and stronger next year. Cut them back to six inches when they’ve died back a bit. Wrap the stumps with straw or cover them with fleece, and keep the ground on the dry side until other growth starts in February.

      • Ben says:

        I’m in a 6′ Greenhouse, I will leave them in as late as possible and see how they go. I saved the seeds from some shop bought fruit that had probably come from a long way south of here but I was hoping they might overwinter. I will cover them with straw and hope. I only have one mature plant but it has set plenty of fruit this year. Thanks for your reply.

        • Andy McKee says:

          I’m impressed! In my tunnel physalis grows 8′ tall by 8′ wide if I let it – nipping it back to concentrate the energy on a smaller amount of fruit is quite a bit of work. Here’s hoping you get lots of fruit next year. The jam’s a knockout.

  2. what is the best time of year to grow cabbage,cauliflower and broccoli in a polytunnel.my fellow allotmenteers are adament the cabbage will not heart up and I will just end up with a huge leaves.They also tell me it that broccoli will not grow well either as it will be too warm.I am in scarborough north yorkshire, are your planting guides based on southern climates?

    • Andy McKee says:

      The dates are middle England, so you’ll need to add a couple of weeks on for Scarborough. As for cabbage, go for a quick-maturing sweetheart variety and you should be fine. You’ll find more detailed information along with variety recommendations in our ‘How to Grow’ book – available from all good retailers or click on the image in the sidebar.

    • Mark Gatter says:

      Hi Jennifer,
      Just thought to add that I grew broccoli in the polytunnel for the last two years and it’s been the best, and the biggest, that I’ve ever grown. Go for it! It’s not too warm. They love it.

  3. Bob Bowen says:

    I am gardening from March to October in Southern Brittany, which has a better climate than my native Lancashire.

    Just coming to then end of my first year in a 10′ x 10′ polytunnel.I used your book as my ‘bible’ though limits on space meant this first summer I only grew Tomatoes, Sweet peppers, Aubergines, Charantais melons, and water melons direct in the soil. I moved Pthallis and chili’s in and out in pots as the weather improved.

    Three Charantais Melon plants produced over 30 melons between the end of August and the beginning of October, we got sick of them eventually. Two water melon plants produced 4 water melons.

    I will try and over winter Broad Beans, Peas, Beetroot, chard,cabbage and cauliflower. Timing might be an issue, I sowed everything the second week in September and my broad beans are already showing signs of developing flower buds (there 6 to 8 inches high).

    Watering has been an issue as we usually leave the house for up to 4 weeks at a time. Using a soaker hose on a timer fed from a 220ltr water butt seems to have worked well,with plastic ground cover material topped with wood chippings around the plants.

    The polytunnel has withstood the weather extremely well. We had a terrific hailstorm in July which marked all the growing butternut squash, apples, and kiwi grown outside but the tunnel came through unscathed.

    Already planning for next year,I will try a greater variety of veg.to extend the season rather than the gluts this year produce.

    Thank you for passing on your experience and knowledge.

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