Polytunnel Growing for Beginners – Complete Guide!


Polytunnel Growing for Beginners – Complete Guide 

If you want to start cultivating your personal crops of veggies and herbs, or flowers, etc., or if you want to broaden your horizons and extend the actual growing season, then it would be best if you considered obtaining a polytunnel.

In a perfect climate, a polytunnel can enhance the number of plants you can effectively produce. It will enable you to cultivate vegetables throughout the year.

A polytunnel can provide some protection from the whims of the weather. If it’s properly constructed and operated, it can also help to lessen pest problems. A polytunnel is not just a cheap greenhouse – it’s so much more.

The inside of a polytunnel warms up because incoming solar radiation from the sun warms plants inside the building faster than heat can escape from that structure. Hot inside surfaces warm the air quickly, and that heat is kept in the building by the roof and walls. Hence, the fixed equipment in the polytunnel controls the humidity, temperature, and ventilation. Otherwise, the control comes from the manual opening and closing of the vents. Polytunnels are mainly used in temperate areas, similarly to glass greenhouses.

It is a tool that can help you grow plants more successfully than you ever imagined. Consider a polytunnel to be an elongated oval plastic tent! Then you will have a much better idea of what you can plant in one.

What is a Polytunnel?

A polytunnel is a polyethylene tunnel elongated and stretched out in a long caterpillar, semi-circular shape. They are like a greenhouse in terms of functionality. A cloche is a cover used for the same effect with single plants, whilst a greenhouse is much larger and frequently made of glass.

The primary purpose of polytunnels is to produce a microclimate with greater temperatures and humidity. This allows you to cultivate a variety of fruits and vegetables even when they are out of season. They are also great for crop protection, shielding plants from the elements like heat, cold, wind, rain, and direct sunlight.

A polytunnel also has the advantage of being a temporary structure. It is almost effortless to shift it around or take it down totally.

Kitchen gardens for herbs and salads can be grown in smaller polytunnels or hobby tunnels. On the other hand, the enormous ones can be used for everything from growing full food crops to operating plant and flower nurseries.

Most significantly, a polytunnel allows the gardener to cultivate fruit and vegetable plants.

Plants that would not be able to thrive in their natural environment. They also lengthen the growing season, allowing you to cultivate your favorite foods throughout the year. The large range of polytunnel equipment widely accessible allows for easy control of temperature, humidity, watering, and ventilation.

Purchasing, maintaining, and installing polytunnels is substantially less expensive than purchasing, maintaining, and installing greenhouses. Polytunnels are also quite simple to erect and manipulate.

The most commonly used polyethylene or polythene film biodegrades naturally over time. It will typically last 3 to 10 years before needing to be replaced, depending on usage and location.

Advantages of a Polytunnel

As previously said, a polytunnel allows you to grow fruits and vegetables that would otherwise be impossible to grow in your environment. Polytunnels can extend the growing season for many months in warmer climes (sometimes all year round).


Controlling and adjusting humidity, watering, and airflow is simple. Polytunnels are far less expensive than greenhouses, and they are also a lot easier to set up and maintain.

Crops grown in the polytunnel thrive in any season, with the best germination conditions in the early spring due to higher sunshine absorption.

If you correctly insulate your tunnel, it will stay cool in the summer and keep your plants alive in the winter.

The ability to add a basic yet effective irrigation system makes it much easier to produce cros in the tunnel.


In the polytunnel, it is possible to establish a ‘Mediterranean climate, which means you are able to produce more exotic fruits and vegetables.

You may extend the growing season even further by wrapping it in bubble wrap during the winter. You can remove the bubble wrap when the winter season is finished and reuse it the following year.


As already remarked upon, polytunnels are far less expensive than greenhouses, and for the same price as a small greenhouse, you can build a polytunnel that is 4-5 times the size.

Polytunnels can be moved around the garden more readily, making crop rotation more convenient.


The majority of fruits and vegetables sold in supermarkets are grown in polytunnels. Polytunnels are becoming increasingly popular among farmers as a green way to boost crop yield.

Farmers who were previously only able to cultivate certain crops owing to their climate (for example, in the United Kingdom) can now grow Chile, tea, coffee, kiwis, and grapes.

Things to Look When Buying or Building a Polytunnel 

Tunnel Size

What tunnel size do you require? In many situations, the standard 14 or 18 ft is ideal, but it can be as long or as short as you want. The length will usually be in 6 ft multiples due to the construction style. On a lesser scale, there is no reason why low tunnels can not be used.

Polytunnel Orientation

A polytunnel is best built on level terrain and can be positioned to catch the most of the light. If your land is on a slope, however, placing the polytunnel down the hillside makes it a lot easier to deal with and creates natural ventilation.

Polytunnels Access and Doorways

Smaller polytunnels usually include access doors at the ends. In bigger commercial polytunnels, however, side access portals are possible.

The size is entirely up to you, but most gardeners believe that making them too small is pointless and that full-width entrances are preferable.

The doors are usually hinged to a wooden frame and open outwards, therefore not taking up growing space in the doorways.

Conversely, commercial gardeners utilize a sheet of plastic on battens that fit the tunnel’s end like a blind. Hooks and pins (six-inch nails inserted into a hole in the frame) hold it in place, and they simply remove it when they need access on foot or with a tractor.

Irrigation in Polytunnels

Normal watering can suffice in small tunnels. However, if the area covered by tunnels grows, you may wish to consider simpler options.

Overhead irrigation is simple to install and operate. It usually comprises PVC pipes with several spaced nozzles facing upwards. They can be glued into long lengths to prevent dripping when turned off.

Connect to a water supply, turn on the faucet, and a small mist of water will suffice. It’s great for lettuce, celery (a marsh plant), and cucumbers (that enjoy the dampness in a tunnel), but you need to be more cautious with crops like tomatoes.

Tomatoes are susceptible to blight since they are solanum plants. It’s the same species as potatoes but highly susceptible to blight. This is spread by water splashes and thrives in heavy humidity and rain. As a result, drip irrigation is the greatest option here.

The most basic are perforated rolls of plastic tubing or seep hose, but it’s been found that these are inefficient over long distances since the pressure drops rapidly and one end of the row gets too much water while the other end gets none.

Gardeners prefer drip hoses with nozzles. Each nozzle drips a specific amount of water every hour, drop by drop. Most gardeners use ones that drip at a rate of 4 pints each hour.

As a result, they know exactly how much water is being added. If you give tomatoes too much water, they will grow vertically and produce less. However, yield is lost when plants are submerged.

Polythene Type Choices for Polytunnels

There were few options when grown commercially. Tunnel ‘liners’ don’t last long, and although three seasons was considered adequate – they were blown apart by the wind, and degraded in the sun, which was an issue.

Today, the film contains additional inhibitors, which last for several years.

They are well worth the extra money, even though they are more expensive. So, choose according to the weight; some people prefer 600 microns, but other weights are also accessible.

Take into account also the inhibitors in hand. There are a plethora of speciality Polytunnel companies on the internet, all of which carry a variety of plastic sheeting.

Snow Loading on Tunnels

In polytunnels, snow can be a concern. We have seen tunnels collapse under the weight of snow, which wreaks havoc on gardeners.

Snow is beneficial in small amounts since it insulates the tunnel and benefits the crops. Assuming it does not turn off the lights for several weeks.

However, a few days or even a few weeks without light does little harm. After all, if your lawn grass can survive, why can’t other crops? Use a broom to gently shake the plastic from the inside to remove snow. Unless it is completely frozen, it will readily fall off the plastic.

Polytunnel Tube Type

Metal tubes bent into an arch are commonly used to construct tunnels. These might be sectional with top joiners. In the case of smaller tunnels, a single piece of tube that covers the entire length of the tunnel can be used.

My friend’s first amateur tunnel was fashioned out of a 19mm water pipe that had been bent over a framework. The issue is that curves are rarely perfect; this isn’t a problem with small sizes, but it’s not ideal on a bigger scale.

Aluminum is the most common material utilized in the construction of commercial and bigger amateur tunnels. It is both light and powerful.

Alkane piping, on the other hand, can be used for tiny, cloche-like tunnels. It doesn’t need to be pre-bent; simply bend it into shape by hand as desired, and it will spring back when released.

Ground anchors hold the tunnel hoops in place. The hoops are held in place by steel tubes driven into the earth.

Several holes are bored through, then pins (larger nails) are used to hold the liner. This process helps to prevent it from slipping too far and tensioning it once in place.

Things to Consider for Effective and Successful Cultivation for Beginners in Polytunnel Growing 

Vegetables and fruits flourish in a two-element environment. The climate refers to the area above ground where the plant develops.

The second element, which is where the root system expands, can be soil, specialized soil, a water solution (hydroponics), or a suspended root system (aeroponics).

The quality and production of a crop area are affected by cultivation practices and subsequent care of all plant sections.

When growing a specific variety, you must first learn about their needs and then alter the atmosphere in the polytunnel to match these needs as closely as possible.

In a polytunnel growing, the plant thrives as a result of this, growing, blossoming, and producing fruits.

Such endeavors necessitate effort both before and during the growing season. As a result, when deciding on species to plant, it is critical to investigate and identify the best location for such planting.

In this way, the number of jobs is reduced. Vegetables and fruits benefit from favorable conditions without having to invest additional funds. It’s important to remember that conditions can change during the plant’s development.

The effect of systematic situation control and suitable actions on yield is beneficial.

The term ‘climate’ refers to a collection of interrelated elements that influence the appropriate growth and development of vegetables and fruits. Light, temperature, precipitation, air composition, and microclimate produced directly by plants are among these elements.

Light is the essential climatic component. It supplies the necessary energy for photosynthesis to occur.

Organic matter and oxygen are produced as a result of this process. The glucose generated is then utilized by fruits and vegetables for further processing. It converts to starch or fat when stored in stems and roots.

More light

Light alone influences plant growth and development in addition to photosynthesis. This is referred to as a photomorphogenic process.

Throughout their whole existence, light regulates the events that occur in plants. Maturation, germination, green mass formation, flowering, fruiting, and ageing are all light-dependent.

Whether or not they are short-day or long-day plants, the flowering of vegetables and fruits is determined by the group to which they belong.

This phenomenon is identified by examining how long the plant can develop with continual access to light during 24 hours.

Plants across diverse latitudes respond to local conditions in different ways. Kale, lettuce, and arugula, for example, are shade-loving plants.

They thrive in gloomy situations because they are accustomed to low light intensity. Plants that thrive in direct sunshine, such as peppers, tomatoes, and zucchini, are thermophilic.

At certain seasons of the year, light intensity drops dramatically in particular latitudes.

In the autumn and winter, the amount of light available is insufficient to allow plants with high light requirements to grow to their full potential. Polytunnels, greenhouses, and garden tents with artificial illumination are used for this purpose.


Temperature is the next important factor in crop development. Crop development is greater and faster when the temperature is optimal.

Depending on the stage of development and the intensity of light, appropriate levels may be necessary. At different stages of plant development, such as sprouting, blooming, and fruiting, different demands emerge.

Fruits and vegetables have distinct features based on their species, and certain types are resistant to freezing conditions.

Their growth is slowed if the temperature falls below the minimum value. Although certain perennial vegetables can resist temperatures as low as -20° C, the bulk of crops cannot thrive below 5° C.

Cucumber, tomato, and pepper are heat-loving plants, extremely sensitive to cold, and temperatures below 0 can permanently harm them.

The intended crop may not survive if proper conditions are not produced during the various growth stages. They may not be able to produce blooms, fruit or attain their desired shape on time.


Crop quality does not depend on the number of raindrops but rather on their content and frequency. Your crop will have a bitter and woody flavor if you don’t get enough water regularly.

Excess, on the other hand, reduces the amount of dry matter, washes away nutrients, and increases the risk of disease infection and pest attack.

Although the cover prevents rain from entering the Polytunnel, Irrigation systems will provide a consistent and reliable source of water.

There are a variety of basic strategies to prepare yourself. Capillaries, sprinklers, and mechanical installations with sprinklers are examples of do-it-yourself drainage gutters for rainwater from a tank.

Small hobby tunnels, as well as professional multi-chapel complexes, can benefit from these technologies.

A polytunnel enables you to alter the area’s watering levels without incurring extra fees. Moisture indicators, which are readily accessible on the market, can be used to accomplish this.

Private polytunnels already have these features, and they are becoming more affordable each year.

Snow, which develops a snow blanket, and hail, which occurs rapidly, are examples of precipitation. Field crops are harmed by severe weather conditions in both scenarios. The tunnel’s foil top acts as a protective covering for the veggies and fruits inside.


On the plantation, the air circulation under cover is beneficial. It dries up leaves, minimizing the development of infections and fungal or mold problems. Self-pollination of plants is also aided by the wind. However, if the gusts are too powerful, it might be dangerous.

Plants that are overcrowded or injured fall off and decay on the ground. Horticultural tunnels use foil to keep high winds at bay.

With a handful of doors, single or multi-vegetation tunnels with side ventilation can create beneficial air movement inside the structure without causing negative consequences.

Strong air movements are especially dangerous to plants with a sensitive root structure.

Cucumbers, beans, asparagus, and clinging bushes may break if not properly protected. The location of such a building has an impact on the conditions in the garden polytunnel as well as the crops themselves.

If it’s near a forest, the microclimate inside will be different than if it’s set up in an open area. A polytunnel pointing south will provide significantly better soil heating, warmer air, and a longer exposure time.

The lowering of temperatures and discrepancies between day and night will,  however, be influenced by the vicinity of a huge water reservoir. Place your polytunnel on light slopes for drying rather than exposing it to flooding by placing it in holes.


Vegetables place a lot of demands on the land. The soil cannot be too heavy and wet.

Nutrients and water content are two factors that influence growth. Regardless of the species or variations, the humus layer must be thick so that the plants can draw from its micro and macro components.

The nutritional and growth processes will be considerably more favorable if the soil structure is bumpy. For a wide range of vegetables, the ideal soil PH ranges from 6.2 to 7.5. There are, of course, exceptions in which Ph must be matched.

Cauliflower, cucumber, celery, Chinese cabbage, and onion are the most demanding.

You can expect substantially higher crops if you take care of your land. Every polytunnel gardener’s obligations include adhering to deadlines, executing jobs on schedule and also, delivering nutrients to plants through substrate fertilization.


The right plant rotation has an impact on yield. Soil tiredness is caused by cultivating the same species of plants from the same family, resulting in low yields. Diseases and pests common to the crops in question can grow and have an impact on the plantation.

A lack of rotation can also result in acidification or salinity. Cleaning and fertilization of post-season producing areas are required. Crops that have already been harvested must be redistributed and replaced with new plantings.


To ensure high-quality output, you must meet the nutritional requirements of the plants. Appropriate doses of mineral or organic fertilizers are applied, either directly or indirectly, to this aim.

The soil provides a large portion of these elements for crops and fruits.

Every action should be preceded by a soil study. So, that you can enrich the soil favourably and to its greatest benefit while bearing in mind the shortages.

Basic soil analysis is a low-cost service that ensures a greater harvest. A decrease in quantity and quality is always the result of improper dosage and fertilization.

Final Thoughts By Patricia Godwin

There you have it – Polytunnel Growing for Beginners – Complete Guide 2021! What a revelation! What an innovation! How wonderful the world is that we can create these amazing contraptions that benefit both nature and mankind in a futuristic manner.

Even if you knew nothing about this kind of thing when you commenced reading this article, I imagine you are quite the expert now. I also think, if asked, you could explain it all in a rational manner and sound like a professional!

This article has been written for you in such a comprehensive manner that it contains everything you need to know on the subject….and probably more.

I hope you succumb to the temptation of erecting a polytunnel and experiencing all the wonderful benefits it can bring to you.

As stated earlier in this article, a polytunnel is not just a cheap greenhouse – it’s so much more. It’s the ultimate in creating veggies, flowers and everything else you want to grow.

Greenhouses were great in their time – but are becoming so yesterday. Why settle for that when you can enjoy tomorrow right here and now!

Enjoy this beneficial adventure and have fun with your polytunnel!


Jenny Marie

Tribal Writer



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Patricia Godwin

Patricia Godwin

Patricia has many years of experience as a content writer on various subjects, but her first love is gardening. She’s never met a plant she didn’t like and, consequently, she writes about every type of plant you can think of. Once an avid gardener with a herb garden, a succulent rockery, and a rose garden – to mention a few. Nowadays, she’s constantly on the move searching for interesting plants to bring to your attention; and explain to you all the details you need to grow, care and maintain these plants.

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