Growing under cover is one of the most effective ways to get better results from your garden in the UK. Whether you’re using a traditional greenhouse or a polytunnel, the core principles are the same: protect plants from the weather, extend the growing season, and create a more stable environment for growth.
This guide explains how to use a greenhouse or polytunnel properly, what you can grow throughout the year, and how to avoid the most common beginner mistakes. If you’re new to growing under cover, you may also find it useful to explore our greenhouses and polytunnels hub, which brings together all of our related guides in one place.
🌞 What Does a Greenhouse or Polytunnel Actually Do?
At its most basic level, a greenhouse or polytunnel traps solar heat, protects plants from wind and heavy rain, reduces pest pressure, and creates a more controlled growing environment.
This warmer microclimate allows plants to grow faster, stronger, and for longer than they would outdoors. In general, greenhouses tend to retain heat more consistently, while polytunnels warm up quickly during the day but lose heat faster overnight. Both systems work extremely well when used correctly and matched to the space you have available.
For more guidance on choosing the right greenhouse and understanding how different designs affect growing conditions, see the RHS guide on choosing greenhouses.
📍 Where to Position Your Greenhouse or Polytunnel
Good positioning makes a huge difference to how successful your greenhouse growing will be.
Ideally, your structure should receive plenty of sunlight throughout the day, with a south or south-east facing position working best in most UK gardens. Some shelter from strong winds is important, especially for lighter structures, and the ground should drain freely to avoid standing water.
For smaller gardens or patios, a lean-to greenhouse fixed against a sunny wall can be an excellent space-saving solution while still providing good growing conditions.
🌱 What Can You Grow in a Greenhouse or Polytunnel?
One of the biggest misconceptions is that greenhouses are only useful in summer. In reality, they support productive growing almost all year round.
🌱 Spring
Spring is ideal for raising seedlings such as tomatoes, peppers, and chillies, as well as early salads and herbs. A mini greenhouse is ideal for seedlings at this time of year, especially if you’re short on space or just getting started.
☀️ Summer
Summer is when most greenhouses are at their most productive. Tomatoes, cucumbers, peppers, chillies, and aubergines all thrive in the warmer, sheltered conditions.
🍂 Autumn
As temperatures cool, greenhouses allow you to keep growing salads and herbs for longer and provide a protected space for overwintering young plants.
❄️ Winter
Even without heating, a greenhouse or polytunnel can support hardy winter crops such as spinach and salad leaves, while also giving you a head start on early sowings for spring.
🪴 Growing in the Ground vs Pots and Grow Bags
You can grow successfully in a greenhouse or polytunnel using several different methods.
Growing directly in the ground works well for long-term crops like tomatoes and cucumbers and helps retain moisture, though it does require some attention to soil health over time. Pots and containers are very beginner-friendly and easy to manage, making them popular in small greenhouses. Grow bags are also widely used, particularly for tomatoes and peppers, but they need regular feeding to keep plants healthy.
Many gardeners use a combination of all three depending on the crops they’re growing and the space available.
🌡️ Temperature Control: The Key to Success
Learning to manage temperature is one of the most important aspects of greenhouse growing.
Ventilation is essential, even on mild days, to prevent overheating and reduce the risk of disease. Doors and roof vents should be opened whenever temperatures rise. At night, greenhouses tend to hold warmth better than polytunnels, which may benefit from fleece or insulation during colder periods.
If you plan to grow through winter, even minimal heating can significantly improve results, especially in smaller structures.
💧 Watering and Humidity
Plants grown under cover dry out much faster than those outdoors, particularly in warm weather.
Watering in the morning is usually best, as it allows excess moisture to evaporate during the day. Avoid leaving leaves wet overnight, and make sure there is enough airflow to prevent damp conditions building up. Striking the right balance between moisture and ventilation helps keep plants healthy and productive.
🌼 Feeding Plants in a Greenhouse or Polytunnel
Because plants grow more quickly under cover, they also use nutrients faster.
Once plants are established, regular feeding becomes important, particularly for fruiting crops such as tomatoes and peppers. Feeding little and often is generally more effective than applying large amounts infrequently, and overfeeding can cause just as many problems as underfeeding.
🐛 Pest Control Under Cover
Warm, sheltered environments can attract pests if problems are left unchecked.
Common greenhouse pests include aphids, whitefly, fungus gnats, and slugs. Good hygiene, regular checks, and proper ventilation go a long way towards preventing infestations. Catching issues early makes them much easier to manage without resorting to harsh treatments.
🔍 Greenhouse vs Polytunnel: Practical Differences
Although growing techniques are largely the same, there are some practical differences between greenhouses and polytunnels.
Greenhouses are generally sturdier and better at retaining heat, making them well suited to patios, smaller gardens, and year-round use. Polytunnels usually offer more growing space for the price and are ideal if you want to grow crops in rows or produce larger quantities of food. If you’re still deciding which option suits your garden best, comparing a greenhouse vs polytunnel can help clarify the choice.
⚠️ Common Beginner Mistakes to Avoid
Many new growers struggle for similar reasons. Overwatering, poor ventilation, overcrowding plants, ignoring temperature spikes, and forgetting to feed crops are all common mistakes. Avoiding these alone will put you well ahead of most beginners.
🌿 Is Growing in a Greenhouse or Polytunnel Worth It?
For most UK gardeners, the answer is yes.
Even a small greenhouse or polytunnel allows you to grow more food in less space, start earlier in spring, continue later into autumn, protect plants from bad weather, and enjoy more reliable harvests overall.
🌾 Final Thoughts
Learning how to use a greenhouse or polytunnel doesn’t require expert knowledge, just an understanding of the basics and a willingness to observe how plants respond. Once you grasp how light, temperature, water, and airflow work together, growing under cover becomes straightforward and rewarding.
Whether you choose a compact greenhouse for a patio or a larger polytunnel for food production, the skills you develop apply across both. Start simple, build confidence season by season, and use your greenhouse or polytunnel as a tool to make gardening more reliable and enjoyable.
❓Greenhouse & Polytunnel FAQs
How do you use a greenhouse for the first time?
To use a greenhouse for the first time, start by focusing on light, ventilation, and watering rather than trying to grow everything at once. Begin with simple crops like seedlings, salads, or tomatoes, and learn how temperature and airflow change throughout the day. Understanding these basics is the key to learning how to use a greenhouse successfully.
How do you use a greenhouse throughout the year?
Knowing how to use a greenhouse year-round means adapting what you grow to the seasons. In spring, it’s ideal for raising seedlings; in summer, for heat-loving crops like tomatoes and peppers; in autumn, for extending harvests; and in winter, for hardy greens or early sowings. Even unheated greenhouses provide valuable protection in colder months.
How do you use a greenhouse without overheating plants?
One of the most important parts of learning how to use a greenhouse is managing heat. Ventilation is essential — doors and roof vents should be opened on warm days, even in spring. Overheating is a more common problem than cold in UK greenhouses, and good airflow helps prevent plant stress and disease.
How is using a polytunnel different from using a greenhouse?
The fundamentals of how to use a greenhouse or polytunnel are very similar, but polytunnels tend to warm up faster during the day and cool more quickly at night. Greenhouses usually retain heat better and suit smaller gardens, while polytunnels offer more growing space and work well for growing crops in rows.
What is the easiest way to use a greenhouse for beginners?
For beginners, the easiest way to use a greenhouse is to start small and keep things simple. Focus on a few reliable crops, grow in pots or grow bags, and check plants daily for watering and ventilation needs. Building confidence gradually is far more effective than trying to maximise production straight away.
Do you need heating to use a greenhouse in the UK?
Heating isn’t essential to use a greenhouse in the UK, but it can extend the growing season. Many gardeners successfully grow without heating by choosing suitable crops and using fleece in colder weather. Learning how to use a greenhouse effectively often matters more than adding extra equipment.
How long does it take to learn how to use a greenhouse properly?
Most beginners find that learning how to use a greenhouse takes just one growing season. By observing how temperature, watering, and ventilation affect plants over time, you quickly build confidence. Understanding how to use a greenhouse comes from regular checks and small adjustments rather than expert knowledge.
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