Poly-tunnels ??

[Char]

I've had one for donkeys years now, but I stopped using it for growing several years ago because it gets too hot for plants during the summer, so the poor things been relegated to hardening off plants from the greenhouse before planting out side.

I know several of you use poly-tunnels to grow your veg and I was wondering how you keep the temperature down during the hot spells - I can't cover it with shading because it's too big.

Any hints and tips would be gratefully appreciated,
Thanks
Char

[niemeyjt]

How about replacing polythene with netting to keep off bugs and beasties and reduce pest damage?

Then you can use it throughout year again

[Bayleaf]

We invested in a small polytunnel last year, that boasts "toutes les quatre saisons", as the sides roll up during summer months. Looking forward to seeing it properly in action. At the moment, there's just the last of the kale waiting to be devoured.

NJT's suggestion is a good one, but if it's that big, that may be too cumbersome. You could still add netting (like the green fleece) put up on the inside, but that sadly won't stop the heat.

When we had big polytunnels, when we were selling stuff commercially - it was just too hot for anything in summer, and in fact one year, we put the above-ground pool in one of them, for the kids to enjoy while I worked! It was like a sauna in there, but beautiful in the water!!

Haven't really helped your predicament though. Some suggest water sprayers to keep temperatures down.

[L Austin France]

Our 8m x 5m tunnel has a door at each end for through ventilation & gravel path through the middle which can be watered to keep the temperature down by the Latent heat of evaporation and all that physics stuff
Not cleaning the polythene of all the naturally occuring muck that accumulates also provides a bit of shade but lets in enough light.
It's never really been too hot for the Toms, chillis & peppers we mostly grow.

[Quiksilver]

I sympathise, Char. Ours has a big door one end, and we take the plastic off the other end from March onwards, to reveal green mesh, but it still gets up to 40°+ in summer. I water copiously to compensate, which isn't necessarily good for the plants. One solution is to use ropes criss-crossed over the plastic so instead of the edges being buried, you can do as Bayleaf says and roll up the sides. Personally, I wouldn't trust that to resist a tempête and it's a bit of a faff having to roll up and roll down in changeable seasons.
Cats..I recommend cats Ours love climbing (read: ripping) over the plastic, so it's now got natural ventilation.
Or do like some friends did, and renounce on overwintering anything in there, replace the plastic with green mesh. It still provides a bit of frost protection, but it's practical for summer growing too. That's what I'll do when I can't stand the old plastic anymore and I've found a lovely, big, strong (tall) man to help

[Spectrum]

As a poly tunnel virgin but not a greenhouse one, I intend to use a overhead misting system, Iam also using growbags on staging to grow all the plants in, a few reasons, no bending down, no digging, and new soil every year so no need to rotate, they will have a drip irrigation for each plant, my water "Controller" has two output/timers, so one will be for the plants with a moisture sensor and the other output will be for the over head misting system. It should work and I have had all the parts for a while so no extra expense.

[L Austin France]

As a poly tunnel virgin but not a greenhouse one, I intend to use a overhead misting system, Iam also using growbags on staging to grow all the plants in, a few reasons, no bending down, no digging, and new soil every year so no need to rotate, they will have a drip irrigation for each plant, my water "Controller" has two output/timers, so one will be for the plants with a moisture sensor and the other output will be for the over head misting system. It should work and I have had all the parts for a while so no extra expense.

Good luck with that !
As a gadget man I've tried all sorts of drip irrigation systems. All work fine at the start but eventually succumb to whatever is in the water & slowly 'bung up' leading to uneven watering & constant need for adjustment. It could be that I'm using a constant water height barrel to feed 'em with very low pressure rain water but as the alternative is a high pressure mains & hence chlorinated water supply it's the best I've got. It's fine if you've got the patience to check & regulate 30-40 nozzles but as I no longer have such a thing this year I'm going back to the tried & trusted upturned bottomless plastic bottle buried alongside each plant & filled with a hose from the same rainwater source. It's gonna be easier & quicker than groveling on my knees amongst the plants whilst adjusting the drip feeders.

[Bayleaf]

My little polytunnel (about 6mx3m) went over an existing area of raised bed, that's set on a stone surround. The ground isn't level (not much around us is!), so it drains well. All the planting is therefore in the middle, and we have access around the sides. I'll probably also put a plank down the centre of the "bed" to access the middle easier. This means that there is one large expanse of earth, where everything is put in together, and hopefully doesn't dry out so quickly. The medium, which I'll top up this year, is made up of very-well composted ponkey poo (pony and donkey poo mixed!) and mole hills. One side is sandier for plants like carrots. Stuff grown outdoors, like potatoes, strawberries and suchlike, are grown in old big builder bags or knackered wheelbarrows. We're extremely lucky to have spring water, so can leave the hose on all day, on trickle, and just move it around periodically - it lies on the earth.

This'll be the first year we can start things earlier, so really looking forward to it.

[Hotrodder]

We decided last year to give up growing our own due to increasingly poor results weighed against sheer physical effort. Our small polytunnel rarely developed too much heat (this is Brittany after all) but there was always the option of leaving the door open. We will probably keep it until it self destructs in the next gale using it to grow some plants for our window baskets. We will keep going with runner beans that are happy enough to grow up structure made from hazel branches. The growing potential is dire here. We have some leeks growing directly out of our compost heap that were dug up and left there over a year ago. They are still no bigger than my thumb. Even with the ever rising costs in the supermarkets we are better off not trying to grow our own.

[Char]

Thanks everyone
The sides are well buried in the ground, about 3ft I think, we were determined the gales weren't going to blow it away, so I can't roll up the sides. We have a door each end so I'll try a gravel path and keep it watered.

I don't really want to remove the plastic, because we use it to store the Rotavator, Lawn Mower, circular saw and other stuff over the winter.

I've found an old car radiator fan so I might try connecting that up to a battery and see if I can encourage more air flow.

Reading through all the replies it seems I need to just constantly water things, but not too much.

Still, if we have another summer like the last one, heat won't be a problem but at least I'll get some crops grown.

Those of you who use one regularly, do you grow in raised beds or directly into the soil?

Thanks I appreciate this.