One of the challenges in polytunnel gardening is working out when to remove summer crops from the ground in order to make way for the next phase of planting. Learning when to clear out summer crops from your polytunnel is important when developing a year-round growing and eating system.
There is often a dilemma, in that you may wish to remove plants that are still somewhat productive in order to establish winter crops before the cold weather arrives and the first frosts threaten. Plants may be tailing off in productivity and you may also wish to remove them in order to make way for plants that can deliver a higher and more useful yield for the next part of the year.
In order to help you to make up your mind when it comes to clearing out summer crops from your polytunnel, here are some tips that could help for some of the most common polytunnel-grown edible plants:
When To Clear Out Summer Crops of Tomatoes
If tomato plants have succumbed to blight, a mould or another disease, it is important to clear out affected plants as soon as possible after you have noticed the problem. Any diseased plant material should be disposed of away from growing areas and your composting area – usually they are burned.
If your tomato plants stay healthy, however, the process of clearing them out begins before the end of the season. The key to high productivity lies in trying to get as many of the green tomatoes on the plants to ripen as possible. Check out our guide to getting green tomatoes to ripen more quickly to get some tips on this process.
Around a month or so before the last frost date in your area, it is time to give up on getting any new tomato fruits. Concentrate on the fruits that are nearing maturity. Cut off any new flowers and fruits that form, and cut back on watering.
In my polytunnel, the tomato plants are left in the ground to allow the existing tomatoes to mature until it is time to put in onion sets in autumn. I generally place onion sets for overwintering in the ground in around mid-October. Amid the onions, I may also place some winter greens. These are already growing in pots and containers ready to be transplanted to the growing areas when there is space to do so.
After removing the tomatoes from the polytunnel, I mulch the area with home-made compost/ leaf mould before planting the area up again. This ensures that good fertility is maintained, and helps to keep the soil healthy over the winter months.
When To Clear Out Crops of Peppers
Peppers are also, when healthy and happy, left in the ground or in containers in the polytunnel until shortly prior to the first frosts. Both bell peppers and chilli peppers are still producing well if the weather in early autumn is mild. However, in colder years, I sometimes do provide these plants with a little extra protection from the night time chill. This generally involves covering individual plants with a layer of fabric, or cloches. If a productive plant is in a container, sometimes I also bring these inside in order to allow more peppers to ripen before the end of the season.
Usually, the areas in which peppers were grown are vacated shortly before the first frosts. Often these were grown alongside tomatoes and so are planted up with onion sets and winter greens after mulching as above.
When To Clear Out Crops of Lettuce & Other Leafy Veg
Lettuce and other leafy veg is a little more complex, and it is in this area that the crop rotation plans can sometimes get confused or muddled. Whether or not such summer crops should be removed will depend on when exactly they were planted. There will also be a range of other factors to consider. Since lettuce and other leafy veg can be sown and grown almost all year round in a polytunnel, choosing when to remove these can sometimes be a rather vexed question.
Often, these crops will be used to fill in gaps in the summer planting. You may also have sown leafy veg for winter and to harvest in the hungry gap next year over the later summer months. Even up until September and even beyond, you may still be sowing some leafy greens and lettuces for overwintering.
Of course, summer lettuce and other leafy greens that have bolted should usually be removed there and then. The exception to this is when you are saving some from which to obtain seed.
In order not to deplete the soil, I generally try to avoid growing leafy crops for winter in the same area where they were grown in the summer months. I generally replace summer brassicas and lettuces etc. with legumes (peas and broad beans) for overwintering in September/ October. Field beans are a hardy choice that can easily be overwintered even in colder areas in the UK.
In order to prevent problems with rodents eating the seeds, I generally sow overwintering peas and beans in pots to transplant when the spaces open up, rather than sowing them directly in the ground.
When To Clear Out Cucumbers, Melons & Summer Squash
While winter squash and pumpkins will still be going strong, cucumbers, melons, summer squash and courgettes are likely to be past their peak and are generally removed before the beginning of October. It is generally easy to see when these plants are past their best.
While you can sometimes keep a courgette plant or similar productive well into autumn, I generally choose to remove these in order to transplant tray sown winter lettuce and other winter leafy crops into the space in late September/ early October.
When To Clear Out Runner Beans/ French Beans
If you pick your beans regularly, the plants can continue to produce an abundant crop for 8 weeks or more, between July and October. Generally speaking, these beans are harvested green, before the beans inside begin to swell. However, with certain varieties, you may wish to harvest the beans inside and not the pods, for drying and storing for winter.
Beans that are to be left to mature, and dried are usually not removed from the ground until later in autumn, though beans harvested for the pods are usually past peak production long before this time. When exactly you remove these plants from crop rotation will depend on what exactly you are using them for and which varieties you have chosen to grow.
I sometimes follow summer legumes in my crop rotation with winter brassica, which are grown on in containers in the polytunnel until the space is made available to place them into the growing areas. With summer legumes, the roots are left in situ and the plants simply cut off at ground level.
When To Clear Out Crops of Sweetcorn
Sweetcorn in the polytunnel is usually harvested and cleared by early October. Once the tassels have turned brown, the kernels can be checked for ripeness. If a creamy substance comes from kernels when pierced, the cobs are ready to harvest.
The sweetcorn is usually ready to remove at around the same time as the courgettes/ summer squash, and gaps that are vacated are filled with lettuce and other leafy winter crops. I may also sow some radishes for winter around this time.
These are just some tips to help you think about when to clear out summer crops from your polytunnel. Of course, there are many variables when it comes to gardening. The key to success lies in working out a year round sowing and growing system that works for you, and where you live. Plan ahead and you can continue to eat well from your polytunnel – not just during the summer but all year long.
No matter when you have your main clearing out session, it is important to make sure that soil is left bare as infrequently as possible. It is also important to make sure soil fertility is maintained. Whenever a gap appears, add compost or organic matter to build up the growing area and make sure it maintains good health over the months to come.
When do you clear out summer crops from your polytunnel? Do you have any tips for effective crop rotation? How do you make sure that you keep your polytunnel productive all year round? Share your suggestions for other polytunnel gardeners about when and how to clear out summer crops in the comments below.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.