polytunnel
Polytunnel. Via Bec.w

 

A polytunnel is a tunnel made of polyethylene used to grow plants that require a higher temperature and/or humidity than what is available in the environment. Polytunnels are mainly used in temperate regions and are similar in principle to greenhouses and cloches / row covers.

Constructing a polytunnel is not a small project. A 12ft x 25ft can be constructed in a day by knowledgeable constructors but it’s usually prudent to pencil in two days for a ‘virgin’ constructor. The polytunnel is constructed in three distinct stages. Stage 1 involves placing foundation tubes into the ground into which the hoops simply slot. All other support bars and stabiliser’s are clipped to the frame (like putting up a tent). Stage 2 requires you to fix the doors on the two ends. Stage 3 involves digging a trench approx 12in x 15in all around the framework, the polythene is buried into the trench.

The biggest concern for using a polytunnel on the Western Isles before is wind. Most people tend to think of a polytunnel as a glorified tent, ready to blow away at the first sign of a breeze. Commercial growers could not afford to have their polytunnels damaged by extreme weather and to this end polytunnels have proved their critics wrong in withstanding the most extreme of weather conditions. If the construction instructions are correctly followed then no problems will occur. For those very exposed sites, suppliers recommend purchasing base rails (this helps achieve a tight cover), crop bars and storm stay braces.

Anything and everything can be grown in a polytunnel. Today the polytunnel is used to protect 80% of soft fruit (tomatoes, strawberries, raspberries & blackberries) sold through supermarkets. You probably have eaten a fruit that has been grown under polythene. Polytunnels also protect onions, potatoes, peppers, cucumbers, melons, lettuce, beans and flowers. The list is endless. Prior to the introduction of Polytunnels in the UK only 50% of soft fruit was Grade 1, now it is nearer to 90% – For today’s commercial growers this represents the difference between having a business and going out of business. Over the years all types of plants (flowers & vegetables) have been grown with outstanding results, a large percentage of championship plants have been grown under polythene. The growing season is greatly extended by the protection they offer and many new comers are caught out by the rapid plant growth early in the year.

But are they organic? The vast majority of people would argue that the environmental benefits of using a polytunnel hugely outweigh the environmental costs of its production. Using a polytunnel will significantly reduce the quantity of fruit and vegetable you need to buy, avoiding the associated food miles, energy costs and packaging. Most timber used is sourced from the UK from sustainable forests and has the FSC accreditation. A polytunnel cover should last for around four years, which makes it a fairly small part of the plastic consumption of a ‘Westerner’. The cover can be recycled and be made into smaller covers for cloches and cold frames and a host of other applications around the garden.

The enclosed nature of polytunnels also reduces the need for pesticide and chemical control. A Polytunnel provides an environment that is a natural way to protect plants from disease and the UK weather. Many champions of the ‘Organic’ and ‘Self Sufficiency’ movement own Polytunnels. Buy that polytunnel, enjoy all the extra food it lets you produce – and start totting up the environmental savings.

In general you do not need planning permission for sheds, greenhouses, summerhouses or polytunnels. However you will need to apply for planning permission if the polytunnel is nearer to any road than the nearest part of the house, unless there’s at least 20m between the polytunnel and a road. You can’t build over 3m high (or more than 4m if it has a pitched roof). A pitched roof has its ridge at the centre, and both sides slope down at the same angle – this accurately describes a polytunnel roof.

The tunnels I have chosen are Tufftunnells specially designed to withstand the weather in the Northwest of Scotland. The 10′ and 12′ wide models feature a 3′ (900m) straight side and the 14′ wide has the same space enhancing shape as the standard frame. The frames made from the same size and gauge of tube as their 16′ and 18′ tunnels and maintain the 5′ hoop spacing which they believe makes them the strongest frames available. The recommended coverings are standard or thermal anti-fog polythene. 9.2m wide polythene can be specified for the 14′ tunnel if additional polythene is required in the trench. The door frame timbers are of 3″ x 2″ timber. A twenty five footer comes in at around £500.

Ferryman Polytunnels