8 questions about polytunnels

8 questions about polytunnels

Polytunnels have been used for many years for plant production. It started with professional structures for large-scale crop , then smaller versions were put into the hands of hobby gardeners. The growing trend for home-grown vegetables has contributed to a multiplication of these structures with foil on top in the family gardens. The popularity of greenhouses is also boosted by the fact that they save money and improve health thanks to the resulting supply of fresh, healthy food.

Over a full year, vegetables and fruits represent quite a sum of money. And furthermore, it is unclear whether what gets on our table is free from pesticides and preservatives. A greenhouse is an object created for intensive cultivation, where yields are abundant and controlled.

In which polytunnel to invest?

In a light, mobile, solid structure that can be operated for a long time, easy to assemble and disassemble. These are some of the features to considerate when choosing a foil tunnel. However, these characteristics are the most important if growing is to last more than one season. Unfortunately, many of the products available on the market are too weak or of poor quality. They can corrode, bend in windy conditions, break ( PVC pipes), and work inside is not only uncomfortable, but sometimes brings little benefit. Therefore, in this article, we will advise you how to spend money on an effective polytunnel.

What does it mean to grow under cover?

The basic function of a foil tunnel is to collect sunlight that raises the temperature inside the tunnel. Microclimate created under the cover can be fully adapted and controlled. The grower decides  what conditions are needed inside. This enables perfect matching of air and soil temperature, humidity, air circulation and even sunlight. With the right experience and use of several standard technologies. The gardener has a structure that monitors all the factors influencing the development of plants.

At night when temperature falls, the heat accumulated inside escapes much slower from the facility. By comparison with open field crops, the soil gets colder hour after hour and during the day. The sun must first warm up the soil to create the optimum environment. Proper soil and temperature maintained at the same level ensure that vegetables and fruits have favorable conditions during each growing stage.

Why foil over crops?

As already mentioned, the foil tunnel does not only generate heat but also the right amount of light. This gives far better results than direct light on outdoor crops. In shady areas, plants compete for light. The foil disperses the sun’s rays over the entire object so each plant is evenly exposed, and the stored heat remains inside during cool days or nights. Among foil types, transparent is the most common, although there are also specialized covers:

  •     shading – which limits penetration of sunlight,
  •     anti-condensation – which eliminates collection of water vapor on the cover
  •     pumped – additional air layer that improves microclimate insulation inside the tunnel.
  •     Seasonal and multi-seasonal

As you can see, there is a wide range to choose from. When beginning, the polytunnel should be as simple as possible. At this stage, any over investment is completely unnecessary. It is better to later equip a foil tunnel than to invest in an excessive size. Although it is worth remembering that the inside of a tunnel quickly gets filled up.

How long can you use a foil tunnel for?

It is difficult to answer unequivocally. This depends largely on the structure of the polytunnel. We have often discussed the subject of rack strength in our blog and documents. What does this mean in practice? Even if the garden tunnel is made of steel, it is essential for the frame to be galvanized. If it is already covered with zinc, it is best applied with a hot dip galvanizing method.

This is what gives long use properties to a garden greenhouse.

There are many factors affecting the greenhouse. Such facility will be exposed to weather hazards and ongoing work: storms, hail, rain, and watering inside, humidity and maintenance. PVC is too weak, aluminum is too elastic, wood needs to be refreshed and impregnated, and steel – if not galvanized – corrodes.
When choosing a foil tunnel, you should also check the diameter of elements. A 0.8mm PVC element will not be as durable as a steel one. When steel is made of low quality material. Even a thickness of 1.2mm may be too thin and will not improve strength. Low quality plastic tunnels are cheap, but they usually last two, maybe three seasons. Perennial structures will not get damaged, and the only component that needs to be replaced is the foil.
It is worth asking yourself this question: can I afford to buy cheap stuff?

How to take care of polytunnel?

Any damages affect tunnel performance and crop quality . The corrosion-resistant construction not only becomes susceptible to damage, but also transfers harmful components to the soil. Such “addition” in the soil is not only harmful for the substrate, but also for people consuming crop from such a site.
Damaged tunnels must be replaced as soon as possible, torn foil must be repaired or entirely replaced. Anyway, from one season to another, for harvest to be successful, one has to fertilize soil, lead a correct crop co-ordination and plan crop rotation ahead . Once in a while , the greenhouse needs to be disinfected, using steam, pressure washer or replacing cover.

How to make a tunnel work effective?

Plants in a polytunnel must have ideal conditions to grow properly. However, we tend to forget that a gardener is also working and it is essential to make it comfortable and easy for the user. Height, width, input, work space and usability must be considered at design stage. Oval structures make the sides harder to access, as they narrow the space in the center. You will have to go down, and access is not easy. Zippers, which are present on some tunnels and meant to close the tent tightly, disintegrate quickly. A lack of air circulation creates a suffocating atmosphere while small windows in green tunnels do not create any ventilation.

So how should it be?

The structure should be high enough so that shelves can be placed on the sides of the tunnel , holding pots or planting containers, and wide enough so one can stand and move freely. The sturdy frame should allow hanging of pots, creating additional space for cultivation. Proper ventilation will ensure that air circulation properly occurs inside during operation.

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