The Polytunnel

A big polytunnel.
Six meters wide and twenty meters long.

Predictably, this was a daunting structure to put up.
Predictably, I am seriously pleased with it.



I also predict vast amounts of vegetables, herbs and fruit to be emerging from its doors this coming summer!!!
I will report back on that one.

I started clearing the space for this tunnel last winter. Between many other projects the item 'get ready for polytunnel' never quite got crossed off the list until late summer this year. And this was long after the thing itself (in all its bits and pieces) had been delivered at the beginning of May.
I decided to put the tunnel very close to the road. This is a going to be a centre of intense activity, and it is important to have an easy path for inputs and outputs.
The next thing to consider was how to orient it with regard to the sun. The long axis faces due south, as recommended by the manufacturers.
Shelter, luckily, is a given. I have some trees and hedgerows on all sides of the tunnel. I had to strike a balance there between retaining these for shelter and removing some to reduce shading.
It is possible to do without shelter for a polytunnel, even in an extremely exposed site. I know of large tunnels on islands off the west coast.
You will have to invest in an extra strong framework, which will be that much more expensive.

At the time when I had roughly established the site, a digger was doing some work in the village, and it wasn't long before I asked him to help me put the finishing touches to my work.
This allowed me much better site preparation than I had planned initially.
Adrian, the digger driver, did a neat job.
First, he levelled the whole area, burying branches under under peat soil (outside the footprint of the tunnel), effectively creating raised beds, and tidying up the appearance of this place, in preparation for a garden all around the tunnel.
Then he dug a drainage channel down the middle of the footprint and filled it with stone (6” to 10”).
I later blinded this off with a layer of recycled plastic and fine gravel. This is now the main path, a drainage channel and a heat store, all in one. (Polytunnels heat up quickly in sunshine, but also cool down quickly again. Adding thermal mass always helps.)

Since I had the help of the digger, we added a pond, along the south side of the tunnel.
It is not very deep (about 1m), as Adrian, who has a lot of experience with ponds, was worried about the possibility of the whole tunnel sliding sideways into the pond. He was telling us wild stories about digging foundations for a house in the bog one day, and having the whole site slide into the hole by next morning.
We wanted the pond for - again - a variety of reasons:

• It's fun. And pretty.
  
• We could maybe have fish in it. 
• We could grow water plants in it. 
• Increase of biodiversity. 
• Light will get reflected off the pond and into the tunnel. 
• The area is already very wet and not useful for much else. 
• Aebbhric wants to do bushcraft exercises on a log layed across the pond (sounds like fun if you don't mind getting wet...).

None of us were too sure if the pond would fill up properly (without a liner).
 It was dug during very dry (for South Kerry) weather, filled up within days, and has never looked like drying out since.

So far so good. I was ready to set out the foundations.

I bought the tunnel from Polydome in Birr, Co.Offaly.
It came with a whole book on how to set out the site, do foundations and erect the tunnel.
Overall I am very happy with their product and service. Some things in the booklet could have been expressed more clearly, and I would possibly have made some mistakes if I had not asked more questions.
I am hugely impressed with the fact that they delivered the correct amount of parts. There were many, many moments when I thought they had made a mistake. But it always turned out to have been myself that had jumped to the wrong conclusion.
Erecting a polytunnel yourself is very much like putting up flat-pack furniture.

• It's harder than it should be,
• you wish you had the money to pay someone who knows what they are doing,
• afterwards you see how easy it really was and you consider going into business doing this full-time.

Setting out the foundation is probably the most daunting part of any polytunnel project.
You have to take your time with it, there's no way around that.
I chose a foundation option that was different from the usual:
Normally you dig fairly shallow holes, fill them with concrete, and set 40cm foundation poles into it.
The hoops are later fitted into those foundation poles.

When I first chose the site for the tunnel, I dug a test hole. I dug through two meters of peat before hitting gravel/silt.
Concrete foundations do not 'get a grip' in peat soil. I talked to man from Polydome, and he recommended extra long foundation poles (2.7m).
Polydome also supplies 'Anti-sinkage bars' for boggy ground conditions. They get attached to the foundation poles at soil-level, and, through resting on the soil, prevent the poles from slipping any deeper.
I did not buy any, and used logs from trees felled on-site for the same purpose.

When it came to ramming these poles more than two meters deep into the ground, we had to be a bit inventive. Aebhric would hang on to the top of the pole, and it would go down nearly far enough. Then he would do the rest with the sledge hammer. I had to protect the tops of the poles in various ways.
It was difficult to get them into the positions I had measured out so carefully, as there is a lot of leeway for a the top of a long pole to end up in a different place to where it has gone into the ground.We did our best to keep them level, but still, the positioning is not perfect, and this has impacted on the end result, meaning the plastic is not stretched evenly in some places. But I can live with that.

After the foundation poles were in position, Aebhric was busy with classes again, and I was on my own with the rest of the frame work.
I just kept at it, and bit by bit I got it all assembled over the next few days.

 Summer was over, and I was getting nervous about getting the tunnel done before the weather would turn from bad to worse. Luckily there came a fine spell, and on September 27th, I was able to assemble a crew of helpful people.
Thanks to Adriano, Dessie, Christie, Matthew and Aebhric, we got the huge sheet of plastic unrolled and up over the framework very smoothly.
Adriano, a friend who had put up a  smaller Polydome tunnel the year before, was 'project manager', and relieved to see the cover go on so easily.
I must say, having a friend who has done this before, is psychologically very important.
It is possible to ring the manufacturer with questions, but it is more reassuring to have a friend on hand for all the little uncertainties.
Cutting the plastic sheet to size, for example: It's simple, in theory, to measure the correct length, once, then twice, then cut it.
But it's nice to be able to ask a friend who has done this before: Are you sure now?!

After that my crew helped me fill in the trenches I had dug along the sides of the tunnel. The edge of the plastic goes into those, and then you fill them up with soil. (In my case, again, as peat is a good deal lighter than ordinary soil, we used fine gravel instead.)
We fixed the plastic in a few places along the gable ends, but it was another days' work at least, for Aebhric and me after that, to fix it all securely.

There was an exciting moment when I cut the opening for the door, and I first looked into the fully covered interior of the tunnel. The sun had been shining, and heated the soil inside, so that the tunnel had filled with steam. As I cut the door opening, billows of tropical steam left it, and gave me a first taste of the garden heaven I am to experience in the future.

Why, you may ask, did I not get a smaller tunnel to start with?

• pure greed
• I have been gardening for long enough to know that I am serious about it
• anecdotal evidence suggests that people always want another polytunnel after they've had one for a while
• I want to use the space for teaching

If I had considered a smaller sized tunnel, I would have tried to build one myself, DIY-style.
I may still do that, if I run out of space.

When I ordered that size of tunnel, I did not realize that a 20m tunnel is much higher than, say, a 12m tunnel.
My one is about 4m high. That means I will want to do a lot of vertical growing. I will experiment with climbing plants like beans and tomatoes, of course, but I may also add shelves or hanging baskets.

Lack of ventilation is the root of all evil inside a polytunnel.
It will take some time to find the right combination of vertical planting to still allow for enough air to get through.

People have asked me what I plan to grow, and I say - not very helpfully - 'everything', but I really mean it.
I am planning to grow all the vegetables we like to eat, including many that would do perfectly well outside. (Of those I will only have a few plants inside, for a guaranteed crop, and more outside).
I want to try some things I have never been able to grow before. Tomatoes, and peppers.
I also want to grow as much fruit as possible.
It is so difficult to get high-quality fresh fruit in Ireland, and I miss it.
I will grow strawberries and rasberries. I will get a grape vine and a kiwi. I am also tempted to try an apricot tree and a cherry tree.
All the space in between veg and fruit will be filled with herbs and flowers.
Nice picture isn't it? I will post some pictures of the real situation here later this year.

The truth is, I have no idea how well things will grow for me.
Polytunnel growing is not something you learn in one season.

My soil is not great.
I decided not to import any topsoil.
20m x 6m is a small enough area to attempt some soil amendment therapy. I added a large amount of sand to the peat soil. I got cow manure, which, mixed with straw, is rotting down in piles.
I made a large worm compost pile which should be ready soon.
I will also add grow green manure crops wherever I have space available.
Finally, I bought one ton of 'rock dust'. Peat soil is extremely low in minerals and trace elements. Cultivated soil in general often is deficient in minerals, and Seers' rock dust is a product that is supposed to remedy the situation and improve growing results substantially.
The rock dust should also take care of the PH balance in my case.

The rock dust is still sitting in its large bag outside the tunnel. I am reluctant to add it to the soil indiscriminately, as I want to set up some kind of test to see if it really makes a big difference. I want to add it to some plants, and not to others.
I have heard, in the past, that the soils our food crops are grown in are often very depleted in terms of trace elements, and that therefore the food is not as nutrient-rich as it should be.
I feel that if I am trying to grow food at all, I want to grow food that is not only tasty, but healthy.
Vitamins are not everything. Trace elements are also vital to good health.

One last thing I want to mention on why I am excited about the polytunnel: propagating plants.
At some stage every serious gardener get bit by the propagating bug.
Plants are expensive in the garden centre.
Seeds seem quite cheap, until you get addicted, and want to try a large variety of them every year.
Propagating plants from cutting is a wonderful way to increase your plant collection, or get enough plants together for a hedge.
It seems to me that a polytunnel, with its high humidity, offers ideal conditions for this.

So far, so good. The tunnel is up, the plans are made.
I have even some twenty seedtrays filled with compost and seeds of trees, shrubs and hardy perennials.

I am about to check up on the worms in the worm compost, and later on in the week I will sow some early lettuce.
The recent cold spell put me off work in the polytunnel, but now that it has all thawed out again, there is nothing to stop me from All-Year-Round-Gardening.