How hot is too hot for a polytunnel or greenhouse?

With the extreme temperatures next week, I wondered what everyone is doing about creating shade to keep your polytunnel or greenhouse cool, if you have one?

I have green shading material on my greenhouse (went up in June when we had a sunny period). I also use self-watering containers (buried into the ground to allow more head room for plants). I wet it down as required (up to multiple times/ day is extreme heat) and have a tray of water on the staging to help put moisture in the air. My 10x12 greenhouse has three roof windows (with autovents) and two louvered side windows (also auto vents) and a double-wide door, which is kept open on warm days/nights. I only grow heat-loving plants in the greenhouse during the summer (toms, chillies, etc.) :sunny: :sunny: :sunny:


Blimey, I think I need to up my game! I’m basically torturing my plants with no luxuries haha. I’ve ordered a shade net which arrives tomorrow and watering morning and night. I haven’t been wetting down other than watering as it’s just bare soil. I have had a tray of water in there before which I’lll bring back now. I think for my polytunnel the shade net will be key and the best solution to the heat.

Everything is generally OK but I did notice the new tomato leaves and flowers scorched on some plants last week.

I can not remember what its called but its a spray on white liquid that reflect the heat a bit, so I use that along with shading material, we also have auto vent windows in the roof and rear Louvered window in the back on auto vents, we also have overhead sprinkler system on a timer which kicks in at 06:30 and 20:00 and as @Belovedporcupine says we have a humidity tray on the go to help cool it. we also leave the door open with netting across to keep rabbits and Deer out


That sounds like a very advanced set up! A greenhouse would be lovely one day. Do you mist the tomatoes or just the other plants? I worry about blight on them.

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our tomatoes are in the polytunnel and we have automated watering in their as well, but I hooked a seep hose up to it so it does not water the foliage, we lost a lot of Tom’s to blight last year, don’t want it to happen again. I am always looking into new ways of improving the greenhouse and polytunnel.