Polytunnel on grass

I am looking at getting a Polytunnel as we are hoping to get as self sufficient as possible. I have a couple of sites in my garden which I am thinking about and a couple of sizes of Polytunnel too. The garden is around 125 feet long by 85 feet wide and both sites are in full sun.

After reading the excellent sticky in this forum I was initially looking at a 6x3M blow away. However I visited First Tunnels and am also thinking about a much bigger polytunnel. The blow away would be sited in the current veg plot which has great soil and has been worked on last year.

I would prefer to go big but to do this I would have to site it on a grass area and next to a big tree which would no doubt have huge numbers of roots. I doubt I would find the time to get this area cultivated in time for a tunnel so I would cover the grass and use raised beds. The cost of soil for a 18x36 foot tunnel would be huge though.

I would love to go for the huge tunnel but the work in preparing the ground means I may have to wait till next year. I am also worried about ventilation and the side vents on the big tunnels cost quite a lot. Do you need to have full length side vents on both sides or are the doors at each end adequate.

Your advice would be welcome. Many thanks

 

Much harder to break new ground inside a greenhouse once built; and hot work if the sun is out. In constructing it you will walk all over the area, but IME digging it first, walking on it, and digging it again (indoors) is easier than trying to dig it for the first time indoors. That doesn't solve the tree root problem though.

I have raised beds, on top of an area of tree roots, with some pond-liner between the two (to keep the two separate, and stop the tree roots invading). But that is not inside a greenhouse.

I have NO raised beds in my greenhouse, in fact I have lowered the borders in my greenhouse, to provide maximum cropping height to the "roof".

Glasshouse is best - ventilation and light quality better, and somewhat more thermally efficient (debatable perhaps).

Polytunnel gets you more area for your money, but there is cost & effort in replacing cover periodically. Blowaways are renowned for Zips failing (as well as blowing away of course!)

Worth considering a second hand (eBay) glasshouse, as likely to be cheaper than any polytunnel solution. Needs DIY skills, and there is cost of driving to collect (unless you find one of Freecycle "just next door" )

 

Hi Simon, I'm by no means an expert but I would consider hiring a large rotovator (for a day) to help you break ground if you go for the monster tunnel, but the tree roots trouble me. I would be concerned that they will rob nutrients and water from the tunnels beds, and then in the winter (especially with the storms we have just had) bough break would also be a concern.

With my tunnels I have barely used the vents, and only really done so in the hottest days of the summer, I am in the tunnels daily so the opening and closing of the doors ventilates them well enough for me. A door at one or both ends should suffice, but if you find later you need a second door or a window its easily made up and fitted if you have an average skillset with DIY..

Steve...

 

Thanks all. I went for the 6x3 blowaway and will place it at the far end of my veg plot.