Preparing for winter in a polytunnel garden means planning ahead for the colder months to come and making sure that you are ready for the coming season. A little work now on polytunnel winter protection can prevent a whole range of problems over the harshest time of the year.
Table of Contents
Key Takeaways
- Polytunnels can be useful throughout the whole of the year – even in winter.
- They can be used to grow a wide range of crops, for livestock, or for winter storage.
- There are certain jobs best undertaken before colder weather arrives.
- Challenges in a winter polytunnel can include cold temperatures, wind and storms, pests, diseases, and ventilation issues.
- These challenges can be overcome or avoided with a little pre-thought and preparation.
Using a Polytunnel in Winter
Over winter, a polytunnel, also known as a high tunnel, can potentially be used in many different ways. However, the most common ways to use a polytunnel in winter involve growing crops, keeping animals, storage, or some combination of the above.
Using a polytunnel effectively in winter means thinking carefully about how it will be used, and ensuring that you protect both the structure and what is within it with a little preparation.
Growing Crops to Harvest in Winter & Overwintering Crops for Next Year
Most of those who have a polytunnel will grow year round – keeping crops within the polytunnel not just over the summer but also throughout the rest of the year. Being able to grow crops year-round is one of the biggest advantages of getting a polytunnel in the first place.
Of course, planning and preparation are essential if you want to grow food year-round. To be able to harvest crops in winter, you usually need to sow them in spring, summer and early autumn, before the colder weather arrives.
You will also need to think further ahead, and sow crops to overwinter in your polytunnel for spring harvests. Planning ahead is essential to make sure you can eat homegrown food every month, without experiencing a ‘hungry gap’.
Preparing for winter crops in a polytunnel is something home growers will need to think about months in advance – perhaps even the spring or summer before the winter in question.
Keeping Livestock in a Polytunnel
For some smallholders, crofters or farmers, livestock play a role in rotations. So rather than just planning for crops throughout the year, they might also carefully plan to integrate animals into their overall intentions for the project.
Livestock – a range of different types of animal – might be kept in a suitable polytunnel for some of the year.
Even when they are not kept in a polytunnel year round, letting them spend some time in a polytunnel in winter may be beneficial – both to them, and to the soil, and consequently to the crops that will be grown the following year.
Winter Storage in a Polytunnel
Some polytunnels, depending on their location and the cover that is used, might be used for storage of farm equipment, machinery, wood, or other items over the winter months – or may be partially used for storage in addition to being used in other ways.
Though there may be more to do to prepare a polytunnel for crops or animals in winter, preparing for storage also needs some care and attention.
Challenges in a Winter Polytunnel
Polytunnels generally make things easier, and solve problems on a farm or in a garden. However, there are things that can go wrong, especially over the winter months.
The key challenges for those using a polytunnel in winter tend to be:
- Cold Temperatures
- Wind and Storms
- Winter Pests
- Fungal Problems/ Diseases
- Ventilation Issues
These things can become challenges for those who are growing crops, keeping animals in their polytunnels, or even for those just storing things in their polytunnel over the winter months.
Jobs to Do in a Polytunnel Before Winter Arrives
Getting prepared for winter in your polytunnel primarily means making sure that you have done all you can to forestall potential problems in each of the challenge categories mentioned above. Regardless of how you are using the polytunnel you should:
- Check over the structure to make sure it is in fine fettle, and make any necessary repairs.
- Consider heating your polytunnel (though there is still plenty that can be grown in an unheated space throughout most of the UK).
- Make sure there are no branches or vegetation around the polytunnel that need to be removed before wintry storms arrive.
- Tidy up – a cluttered and untidy space is more likely to attract rodents and other pests.
- Add thermal mass to keep temperatures more stable as temperatures drop.
If you are growing crops in your polytunnel:
- Before winter arrives, plan, and plant crops to eat in winter, and crops to overwinter which will be eaten in spring/ early summer next year.
- Reduce watering – altering settings on an automated irrigation system if you have one.
- Clear out the last of the summer/ autumn crops once they finish producing.
Steps to Ensure Polytunnel Winter Protection
Managing Temperatures in a Polytunnel in Winter
Managing temperature is one of the first priorities for any gardener as the cold sets in. Fortunately, there are several simple, sustainable ways to moderate the climate within your tunnel.
- Add thermal mass: Place barrels, tanks or tubs of water within your tunnel. These absorb heat from the sun during the day and release it at night, helping to even out temperature fluctuations.
- Use fleece and cloches: Lightweight horticultural fleece, mini-tunnels or cold frames inside your main tunnel can create extra layers of protection for tender crops.
- Mulch generously: Organic mulches like straw, compost, or well-rotted manure insulate roots and protect soil organisms from freezing temperatures.
Avoid over-heating, however. While adding heat may be tempting, ventilation remains essential even in cold weather to prevent fungal growth and damp conditions. If you are keeping animals, remember that overheating can be just as much if not more of an issue than things getting too cold.
For those in particularly cold areas, a small, efficient heating option such as a solar-powered fan heater might help maintain frost-free conditions – but many gardeners across the UK manage without any added heat at all.
Preparing for Wind and Winter Storms
Wind is often one of the biggest threats to a polytunnel in winter. A strong gust can loosen the cover or stress the frame if it’s not properly secured.
Before storm season arrives:
- Inspect the cover for tears or loosened fixings, and repair them immediately.
- Tighten the skin if it has slackened over summer. A taut cover handles wind much better than a loose one.
- Check doors and ventilation panels – make sure hinges, catches and frames are sound.
- Clear nearby trees and branches that could fall or rub against the structure.
- Anchor well: For exposed sites, additional bracing or anchoring systems may be wise.
It’s also worth walking around your polytunnel regularly through the season. Early action on a loose flap or a small tear can prevent serious damage later.
Pest Management in a Polytunnel in Winter
Though many pests slow down in winter, a warm, sheltered tunnel can still provide a haven for them. Mice, rats, slugs, aphids and even whitefly may remain active if conditions allow.
To manage pests:
- Keep things clean and tidy. Remove debris and old plant material that might harbour pests or eggs.
- Seal gaps. Check around door frames and vents where rodents could squeeze in.
- Encourage natural predators. Ladybirds, frogs and hedgehogs can help keep pest numbers under control.
- Trap or deter humanely. Ultrasonic rodent deterrents, live traps, or peppermint oil sprays can all play a role.
- Rotate crops and avoid monocultures. Healthy, diverse systems naturally experience fewer pest outbreaks.
Remember that the best long-term defence is a balanced ecosystem – one where beneficial species thrive alongside your crops.
Reducing the Chances of Fungal Issues/ Disease in a Polytunnel in Winter
Damp, stagnant air can quickly lead to problems such as botrytis (grey mould) or downy mildew, particularly when temperatures fluctuate between warm days and cold nights.
To reduce disease risks:
- Maintain airflow. Even in midwinter, open doors or vents on mild days to allow fresh air to circulate.
- Avoid overwatering. Plants need less moisture in low light conditions; keep soil just damp, not wet.
- Water early in the day. This gives leaves time to dry before nightfall.
- Space plants well. Good spacing ensures airflow between leaves and reduces humidity build-up.
- Clean thoroughly. At least once a year, scrub down the polythene and structural parts with an eco-friendly disinfectant.
A clean, well-ventilated tunnel is far less likely to experience major disease issues, even when weather outside is persistently wet or cold.
Preparing a Polytunnel to Avoid Ventilation Issues
Ventilation can be tricky to manage in winter. You want to trap as much heat as possible, yet also maintain enough air movement to prevent dampness.
Here are a few strategies to strike the right balance:
- Install automatic vent openers if possible. These respond to temperature changes, opening and closing vents as needed.
- Create sheltered venting options. Adding mesh or louvred vents allows airflow without letting in strong drafts.
- Use internal divisions. In larger tunnels, use temporary partitions of fleece or netting to manage microclimates for different crops.
- Open up on mild days. Even 10–15 minutes of airflow can make a difference to humidity levels.
Remember, fresh air is just as important as warmth for healthy winter growth.
Can you use a polytunnel in winter?
Absolutely. A well-maintained polytunnel is a year-round asset. In winter it can protect crops, shelter livestock, or store tools and materials. With a little planning, it becomes a productive and sheltered space rather than lying dormant until spring. Many growers use the quieter months to grow cool-tolerant greens, mend structures, or start early seedlings under protection.
How to keep a polytunnel warm in winter?
There are several simple, eco-friendly ways to retain heat in a polytunnel:
Add thermal mass (barrels of water or stone) to store solar warmth.
– Use mulch and insulation to protect roots and soil life.
– Introduce inner tunnels or fleece for double-layer insulation.
– Ensure the cover is clean to maximise light penetration.
– Seal gaps and reduce drafts while maintaining controlled ventilation.
Supplemental heating can be added if you live in a particularly cold region, but for most home growers in the UK, good insulation and sunlight are enough to keep hardy crops growing throughout the season.
Can you grow vegetables in an unheated greenhouse in the winter?
Yes – and this is one of the most rewarding ways to use your polytunnel sustainably. Many hardy crops thrive in the cool, stable environment of an unheated tunnel.
Excellent options include:
– Leafy greens: spinach, chard, kale, mizuna, mustard greens, and winter lettuce varieties.
– Root crops: carrots, beetroot, turnips, and winter radishes sown earlier in the year for late harvests.
– Alliums: overwintering onions, leeks, and garlic.
– Herbs: parsley, chervil, and coriander often keep producing right through the winter months.
By planting at the right time – usually late summer to early autumn – you can maintain a steady supply of fresh produce when outdoor beds have stopped yielding. An unheated polytunnel can provide enough protection to make true year-round gardening a reality, even without fossil-fuel-based heat.
Sources
Qinglu Ying (2025) Greenhouses and Similar Structures. Available at: https://ccd.uky.edu/sites/default/files/2025-09/final-version.pdf [Accessed: 30.09.25]
