Season Extension with a Polytunnel
Ever wished you could enjoy a steady stream of farm-fresh produce year-round? Whether you’re a backyard grower or a small-scale farmer, or grow commercially on a large scale, a well-planned polytunnel setup can help you beat the seasons and maximise harvests throughout the year.
In this guide, we’ll explore the many ways polytunnels serve as powerful plant protection tools—offering shelter from frost, intense sun, wind, and even hungry critters—while also acting as cost-effective greenhouse alternatives. From autumn planting to winter growing and spring seeding, let’s discover how a GROW Tunnel can extend your growing season and transform your growing game.
What is a GROW Tunnel?
A GROW Tunnel, is a type of polytunnel, sometimes referred to as a hoop house, or even a greenhouse. Our GROW Tunnels are a semi-permanent structure made from galvanised steel frames covered in UV-stabilised polyethylene film called ‘Solarweave’. Unlike traditional glass greenhouses, or their modern-day polycarbonate alternatives, polytunnels are affordable, flexible, and easy to install.
They create a controlled microclimate inside by trapping heat and moisture, offering protection from:
Frost: Safeguard crops from early or late-season frosts thanks to the warmer environment inside the tunnel, and creating a barrier from cold air and winds.
Wind: Act as a windbreak to prevent windburn or physical damage to plants.
Excess sun: Solarweave film, filters UV rays and prevents sun stress.
Heavy rainfall: The protective cover reduces the impact from heavy rain and allows for more control over the management of irrigation.
A 6M x 7M Rural GROW Tunnel, ready for planting out.
Benefits of Using a Polytunnel for Season Extension
With a polytunnel, you're not bound by the typical growing calendar, thanks to the benefits they offer in extending your growing season. You can start your seedlings in autumn or even late winter and enjoy earlier spring harvests—closing the notorious 'spring hunger gap'. By creating a controlled microclimate inside, by trapping heat and moisture, GROW Tunnels offer benefits such as:
Creating a warmer growing environment
Both the air inside the tunnel, and the soil temperature are warmer in a polytunnel than if you were to be growing outdoors. The Solarweave film allows a select amount of UV rays to filter through into the tunnel, and with the tunnel sides rolled down, this heat will become trapped inside. Warming up your plants, the air inside the tunnel and the soil in which they grow. This can allow you to grow your summer/autumn crops further into the cooler months, and start your seedlings earlier than conventional outdoor growing.
Protection from frost
When vapour in the air freezes on your plants, you’ll notice ice crystals forming. These crystals damage the plants ability to transport water and damage the cell structure of your crop. Those who have lived through frosts know all too well, the aftermath of a frost leaves behind a brown, shrivelled and almost dead plant. Polytunnels safeguard your crops from seasonal frosts thanks to the warmer environment inside the tunnel, and creating a barrier from cold air and winds, helping your plants survive and even thrive, through the cold winter frosts.
In addition, to these seasonal benefits, a polytunnel can also help prevent damage to plants from extreme weather events, such as:
Excess Sun
Excessive heat can be just as damaging as frost. The Solarweave film installed on our GROW Tunnels act as natural sun filters, especially when paired with shade cloth or side ventilation. This creates a stable environment for heat-sensitive crops during peak summer, preventing sun stress to your plants.
Wind
Whilst a limited amount of wind can help plants develop a strong root system, too much wind can damage your crop. Plants exposed to strong winds can suffer physical damage, ripping them out of the soil. When plants are exposed to too much wind, however, it can take moisture from the crop at a rate higher than it is able to replenish, eventuating in ‘wind burn’. Strong winds can also physically damage your crop, ripping off leaves, flower heads that would develop into fruit, and even pulling your crops’ roots from the ground. Polytunnels act as a windbreak, to prevent such damage, and with the roll-up sides of a GROW Tunnel, you can manage the amount of ventilation your crops need, whilst protecting them from such extremities.
Heavy rainfall
With some record-breaking rainfalls over recent years, more growers are looking for ways to control irrigation of their crops. Periods of prolonged rain, with limited sun, drenches the soil, making your crops water-logged and stunting their growth. If your crop doesn’t have an opportunity to ‘dry out’ the likelihood of fungal growth increases and nutrients that would ordinarily keep the plant alive begin leaching into the soil. When rainfall is particularly heavy, this can also physically damage your crop – resulting in a loss of fruiting flowers, damage to branches and leaves – all making it harder for your crop to thrive. The protective cover of a polytunnel reduces the impact from heavy rain and allows for more control over the management of irrigation. Plus, you can harvest all of that rain from your tunnel roof, for use in the dryer seasons, with the addition of our GROW Tunnel gutter system.
Want to explore all the benefits of growing with a GROW Tunnel? Check out our blog here.
Twin span Commercial GROW Tunnel, being used for nursery stock.
Best Crops for Season Extension with a Polytunnel
Whilst a polytunnel can help extend your growing season, there are still things to consider, such as your external environment and the plants preferences in growing seasons. However, you can get started on each season a little earlier, and continue growing a bit later, with the right management of your tunnel. Here’s a quick guide to growing seasonally in a polytunnel.
Awesome Autumn Crops
Start your winter seedlings: Plant your winter crops in the protected environment of the tunnel, to give them a safe and secure place to get started in life.
Keep your tomatoes thriving: A late harvest of tomatoes can be achieved, late into Autumn if your tunnel is kept warm enough.
Last of the Spring/Summer crops: Expect the last of your summer harvests for crops such as cabbages, spinach, bok choy, salad greens, capsicum and eggplant.
Winter Champions
These thrive in cooler temperatures and perform exceptionally well under cover:
Leafy Greens: A late crop of lettuce and salad greens can be harvested late Autumn/Early winter. Plus, spinach, kale, and silverbeet thrive in the warmer, protected environment of a tunnel over winter.
Root Vegetables: Carrots, beets, radishes, turnips all do well in polytunnels over the winter.
Herbs: Coriander, parsley, basil and chives – bring them undercover before the cold gets to them.
Strawberries: Get a head-start on fresh summer strawberries, by planting them in late winter.
Seedlings: don’t forget to start your Spring & Summer seedlings mid-to-late winter, to get an early harvest.
Spring & Summer Staples
Use your polytunnel to start these crops early and protect them during peak heat:
Tomatoes
Peppers (capsicum & chilli):
Cucumbers & Zucchini
Climbing Beans & Eggplants
Tip: For best results, succession plant every 2–3 weeks to ensure ongoing harvests across seasons.
Check out this video from GROW Tunnels Grower, Conscious Ground, located in Byron Bay.
Setting Up a Polytunnel for Maximum Efficiency
When it comes to extending your growing season, setting your GROW Tunnel up right can help improve your seasonal harvests – and make the growing experience a rewarding one. Here are our tips for planning your polytunnel for maximum efficiency:
Choose the Right Location
When selecting your location, you’ll want to ensure that your tunnel is:
exposed to enough sunlight (north–south orientation preferred),
well ventilated with appropriate airflow around tunnel, and adequate drainage,
on flat land, with earthworks to occur before installation if land is not even,
away from overhanging branches and tree cover to reduce leaf drop and shade.
Determine your growing methods
It’s important to consider how you’ll be growing inside your polytunnel, as there are many options available. From growing in the soil, in pots that can be moved in and out of the tunnel with the seasons, or in raised garden beds (especially if waterlogging is an issue, or even growing hydroponically in your polytunnel. Before getting started with your planting, be sure to make sure you’re working with quality soil, full of nutrients, adding compost to maintain soil integrity.
Succession planting and planning
The key to a year-round harvest is planning ahead. Consider the times required for your crops from seed to germination, and germination to harvest. This will enable you to create a plan for when to plant seeds, and how often to continue succession planting, so that you have an abundance through each season.
Polytunnel Maintenance and Plant Protection Tips Through the Seasons
There are few important factors to consider, that will make extending your season more effective.
Temperature Control
Depending on whether you’re aiming to cool down your tunnel for longer, or make it warmer, you’ll likely need to control the temperature in different ways, such as:
Opening roll-up sides and external Solarweave doors during hot days.
Utilising shade cloth in Summer to prevent heat stress and excess UV.
Install an exhaust fan, to circulate hot air out of the tunnel.
Install heating elements (very cold climates).
It’s a good idea to install smart technology, such as air and soil thermometers to monitor and manage your microclimate, according to the crops you’re growing, providing optimal growth conditions.
Managing Moisture
As your crop will not be exposed to rain under the protective cover of a polytunnel, it’s important to have adequate irrigation in place.
Mulching can help retain soil moisture, and drip irrigation systems help keep moisture consistent. Avoid overhead watering to reduce fungal disease, and utilise a soil/air moisture monitor to know exactly what the moisture needs are for your crop.
Ventilation Techniques
Plants require airflow to avoid mold and mildew issues, that’s why our GROW Tunnels have built-in roll-up sides and both an external (Solarweave) and internal (shade/insect net) door. This allows for passive ventilation, and the ability to control airflow while keeping pests out. Closing vents at night and opening during sunny winter days allows for warm air to enter the tunnel and get trapped, keeping plants warmer overnight. To help with gaseous exchange (bring CO2 out of the tunnel, and a fresh dose of O2 in), you may wish to install an extraction fan as well.
Common Pitfalls and How to Avoid Them
Overheating in Summer
Avoid sealing up the tunnel on warm days. Use side vents, shade cloth, and exhaust fans where required to cool your tunnel down.
Unexpected Frost Damage
Install row covers inside your tunnel during cold snaps for double insulation.
Pest Build-Up
Whilst polytunnels provide a physical barrier to pests and insects, if doors are left open, or your insect net, shade net or solarweave is damaged, your polytunnel can become a paradise for pests if unmanaged. Be sure to keep your tunnel well-maintained, fixing any damage with polytunnel repair tape, close your sliding doors, rotate crops, and introduce beneficial insects like ladybugs where necessary.
A GROW Tunnel is more than a shelter to protect your plants — it’s a powerful, flexible tool that transforms your planting schedule, maximises yield, and ensures you never stop growing. From protecting against extreme elements to nurturing seedlings in winter for spring abundance, the value of season extension is clear.
Start preparing today and escape the “spring hunger gap.” Whether you’re growing for your household or your community, GROW Tunnels are your year-round growing solution.
👉 Ready to extend your season? Talk to the GROW Tunnel team, or get an instant quote here.
