Poly Tunnel

[steve64]

What are the pros & cons of a poly tunnel on the allotment?
The one I am looking at is a 12 by 20 foot £400.00!
Is the better growing environment in the poly tunnel worth the money?
Thanks
Steve.
Essex.

[cheapandcheery]

I would like to hear from anyone with poly tunnel experience too Steve.

Last year I bought a second-hand frame and sent off for the plastic sheet.I went for the slightly more expensive thermal plastic.
Unfortunatley with all the renovation work weve been doing, putting the polytunnel up hasn't had priority.
Now weve decided to move to Bulgaria next year..you'll have to extend your map Andy. I'm not taking the frame but am taking the plastic.

Jill

[PurpleDragon]

I have a poly. I am growing a grape vine in mine and it is well established and the fruits are scrummy. Ripening them off just now ready to wine them. However, in two years, I've never managed to get one single red tomato.

[Merry]

The tunnel on our allotment was quite useful but it blew away in a gale - the cover did that is - and we never did find it!

[Shirley]

I want a polytunnel.... we are in such an exposed area here that it would greatly increase the amount of stuff we can grow. Ours would have to be stronger than the average to cope with winds and snow.

[caithnesscrofter]

I often wonder about polytunnels too.. but, my fear is it will be gone with the wind as we are also very exposed (at the moment). Although, we are planning on starting to build an outdoor kitchen next summer and I am throwing around an idea of creating a wee microclimate within it. Basically build about 6-7 foot cob walls around the outdoor kitchen which will have a lorena stove, cob oven and a rumford fireplace within it. Plant a few wind hardy trees up against the north and northwest walls to carry the cold brutal winds over the top. And with the amount of use the rumford and stove would get on most nights it would create a very cosy little area where you could grow more sensitive subjects. Would take careful planning but, I think it could work, would also depend on how often you used the fireplace and stove though too. But, in the warmer months.. the sun would heat these walls up during the day and would release it's heat at nite when it is needed most.

I'm quite new to the Caithness climate but, leads me straight off to believe that a perenial garden is the way to go and alot less work. But, of course there is always those special fruits & veggies we can't live without! LOL

Perhaps in the polytunnel in really windy areas it would be advantageous to pile sand or dirt around the gaps where the poly meets the ground. That might keep it from "taking off" so to speak?!?

[Shirley]

That all sounds very interesting CC!! We are hoping to try an earth oven build next year...

[hedgewizard]

Hi Caithness, Steve and all. I've just finished my first season with a tunnel, albeit having missed the start of it (only got the thing up in April). Yes, it's absolutely worth it - we've eaten early carrots from the end of May and they've only just stopped growing now, so that has huge implications for how you grow and store your maincrops, but that's just an example. There are some rants about it in my blog. I've just harvested my last cucumber for example, but I am in Dorset.

If your site is exposed, you need to consider your tunnel type very carefully. I'd go for a traditional tunnel, so no screw-in ground tubes; I'd cement the ground tubes in if at all possible; no corner-cutting on burying the "skirt" of the tunnel in (there are no gaps apart from the doors with a traditional tunnel, Caithness!); and choose a film type that inhibits dripping as condensation is going to be a problem. Also, you need to tension the thing when it's warm and that's especially important around the doors. Put a door at each end, because poor ventilation leads to fungal infections. Also, a windbreak of bushes or something is a really good idea on the windward side, if you can do it!

Purple, poor ripening in northern areas is usually down to low night-time temps, so unless you're POSITIVE the temp won't go below 57F at night (oh, look it up!) make sure the doors are closed an hour before sunset. Too much water round the roots also prevents ripening as will trying to support too much growth, so other things you might try include removing sideshoots and flowers that will not develop this season, growing fewer trusses per plant, and stressing the plants by withholding fertilizer and cutting back on water when the fruit is a reasonable size.

[PurpleDragon]

My grapes have just ripened off. I expected them about two weeks ago, and I've been checking daily, but yesterday was the first time I felt happy taking any bunches off. I took about 10lbs yesterday and there are still about 5-6lbs on the vine that aren't ready yet. I took loads of greenery off yesterday too, to force the grapes into taking the goodness instead of the green.

I also lifted about another 20 tomato fruits off my two plants, taking the majority of the green off there as well, and have left about another 15 or so waiting to take. They are ripening off in the kitchen. Next year I shall try your method, Hedgie, to try and ripen them off in the tunnel.

The plants I've been bringing on (floral rather than vegetable) will be going out this week, as Himself is on holiday and can do a lot of the digging for me.

So all that will leave is lots of mess to clear up! Do all my washing down and everything this week as well i think, depending on the grapes.

[Stonehead]

If your site is exposed, you need to consider your tunnel type very carefully. I'd go for a traditional tunnel, so no screw-in ground tubes; I'd cement the ground tubes in if at all possible; no corner-cutting on burying the "skirt" of the tunnel in (there are no gaps apart from the doors with a traditional tunnel, Caithness!); and choose a film type that inhibits dripping as condensation is going to be a problem. Also, you need to tension the thing when it's warm and that's especially important around the doors. Put a door at each end, because poor ventilation leads to fungal infections. Also, a windbreak of bushes or something is a really good idea on the windward side, if you can do it!

Also, consider the depth and weight of snow that can settle on top of the polytunnel. We've had three feet of snow in the mild winters we've had since we've been up here, and the locals have known times when the snow was six feet deep or more. (Drifts are even deeper.)

Three feet of snow on the flat-roofed extension to the house (whose daft idea was that!) can be alarming, so imagine the stresses of that on a polytunnel.

We decided against a polytunnel for now due to the costs of making it strong enough to withstand our condtions, and then possibly have to replace it if the weather proved too much. We have an exposed site with very strong winds - enough to lift and move a heavy 50-bird hen house; heavy snow in winter; and very acidic soil (screw-in tubes get eaten away quite quickly as friends of ours found).

If we ever have enough money to build a polytunnel and keep some in reserve for rebuilding it, then we'd consider one. Even then, we'd have to be careful as we depend very heavily on our vegetable crops and a polytunnel failiure could be catastrophic at the wrong point in the season.

For us, a strong, heated greenhouse would be a useful addition to the sunporch in getting plants started but we mainly grow vegetables that survive outdoors in our conditions anyway. It does lack a little variety at times, but we do get enough to feed ourselves and the pigs, and still have a little left over.

[Shirley]

If your site is exposed, you need to consider your tunnel type very carefully. I'd go for a traditional tunnel, so no screw-in ground tubes; I'd cement the ground tubes in if at all possible; no corner-cutting on burying the "skirt" of the tunnel in (there are no gaps apart from the doors with a traditional tunnel, Caithness!); and choose a film type that inhibits dripping as condensation is going to be a problem. Also, you need to tension the thing when it's warm and that's especially important around the doors. Put a door at each end, because poor ventilation leads to fungal infections. Also, a windbreak of bushes or something is a really good idea on the windward side, if you can do it!

This warmth thing - while the tensioning is happening... as it's not likely to be that warm when we are doing it, can the heat be somehow produced INSIDE the tunnel, or would a sunny autumn day make it warm enough to do anyway?

[HILLDREAMER90]

I found my tunnel invaluble,being in the north of scotland. i went for the biggest heavy duty 1 i could afford, its 30ft + 18 the tubes are 2 " thick & concreted in, the cover was a h d 4 season, i put it in the most sheltered place i could next to the old watermill,at the time had no hedging planted & dident know if it would stand our gales & snow,it did,the cover lasted 10 years [with lots repairs] v important to put cover on a hot sunny day & make as taught as pos.Planted lots hedging all round & some wind break netting.Not much of the cover left on now,think a new 1£150 ish. managed to grow allsorts & great for starting seeds & rabbit protection! Grew aubergines,allsorts beans,chinese veg,peppers,early carrots,celery,cucumber,lots different lettuce,spring onion,mangtout,raddish,sweetcorn,lots toms,baby turnips,lots herbs,basil,bay,dill,fennel,parsley,coriander,ginger in a big pot,siberian ginseng,tobbaco,strawberrys & lots of prettys mingeled in with the veg & my favourite a mini peach tree v pretty blossom feb-march,had to hand pollinate as no bees out that early up here,1 year got abt 100 peaches! tree still surviving but no fruit.Oh & the water came from the burn,put a hose in at top of mill to 2 butts & made some leaky pipes[got silted up a lot] but otherwise worked well & never went dry.Tunnels need lots water & ventelation! not as good as glass for retaning heat,had a cold frame inside the tunnel for tender stuff & seedlings.Got some photos somewhere,will post,when i learn how to. Hope this dosent read as showing off,just enthusing abt polytunnels A.

[hedgewizard]

Sorry Shirlz, missed your post. It can get very hot in the tunnel on a sunny day even at this time of the year, but except where the sun is striking it directly the skin itself will still be fairly cool because of the temperature of the outside air. If you stretch it under those conditions you'll get uneven stretching which will give you flobby bits when the sun goes off the tunnel. So sorry, you'd be best waiting until the outside air temperature is reasonable. I'd think you'd be hoping for 20C or higher.

[Shirley]

Thanks Hedgie....

We'll end up doing that now anyway as the money that we might have been able to scrabble together has now gone on new tyres for David's Landrover - grrrrrr he had one to replace but the garage couldn't find the one that he had fitted so he's had to replace them all. Methinks we could have found a way around it but he's splashed the cash so it's a bit late now.

Hilldreamer - it doesn't read like you are showing off at all. It's great to read all about it. Looking forward to seeing the photos. Muddy posted a guide to posting photos somewhere - CLICK HERE

[cuff]

even if tunnell was put up on a cold day most tunnells can be streched later by pushing up the middle hoops on a warm day like the site by the way