Inside or out?

[Ian in Cumbria]

Hello All

This is not a very topical question given the time of year but here goes. I used the white paint shading on the gh this year. While it did put a stop to the greenback on the toms, it didn't look very "tidy" in our fairly small garden. I have been told to do something neater!. I have just bought some rolls of shading netting (much reduced because of the time of year - no he has none left). I've read on this forum and elsewhere that shading needs to outside the glass or else the shading simply gets hot and radiates the heat inside the gh. This makes sense to me and was what I was going to do. But the instructions on the shading say to fit it inside. I've been thinking about this for a couple of days. Is the point of shading to reduce direct sunlight or heat or both? Is it direct sun or heat or both that cause greenback? If I fit it inside it will reduce direct sunlight just as well as if fitted outside but won't reduce heat. I can reduce heat by ventilation. The shading will be easier (and safer) to fit inside and will not be subject to wind damage. My current thoughts are to fit inside (when necessary) and then ventilate as necessary to keep the temperature as required. Anything wrong in doing this?

Regards

Ian

[peter]

I suspect that it is woven plastic and is not a UV stable sort of plastic and will deteriorate or breakdown.

[FelixLeiter]

The causes of greenback are complex and, as well as high temperatures, insufficient feeding can be the cause. I must emphasise, though, that the shading absolutely must go outside the glass to effectively keep temperatures down. You'll actually find the shading easier to fit and manage if it's outside. If it's wind damage that concerns you, then perhaps the material you've bought is not very robust, which is perhaps why the manufacturers recommend fitting it internally. I use green mesh netting which has the long edge attached to an aluminium tube. This keeps it sufficiently weighed down (it does not have much wind resistance, being netting and all) and allows it to be easily rolled up on overcast days.

[MikA]

The glass allows heat in and traps it - the well known Greenhouse Effect so outside shading prevents the heat reaching the GH proper.

I have a small (8 foot) wooden greenhouse and my solution was to string two pieces of fairly stiff wire on either side of the GH, cut the plastic woven shading to a length to go right over the top and down the other side I then threaded the short ends of the shading onto the wires (2 widths covered the roof). It is then an easy job to just slide the shading into position to cover when the sun is out or tie to one side like curtains when dull (which was most of this summer). Hooking the corners to the screws and a couple of extra cup hooks stopped the wind moving it around too much.

I did try one bright green mesh but it was pretty flimsy, unravelled easily,looked naff and didn't really work so I invested in some heavier duty dark green stuff which looked pretty good and worked perfectly.

[Geoff]

I never shade the greenhouses.

[Monika]

Like Geoff, I never put on shading, but perhaps we are less favoured by the sun in our northern climes!

On the original question, I would fix it outside to stop the sun hitting the glass in the first place, and I do like the idea of using green netting which would allow the air to circulate between the glass and the shading, too.

[FelixLeiter]

As a further thought, like Geoff, I don't actually shade a greenhouse where I'm growing tomatoes. I'll only shade a greenhouse if the plants within actually require it.

[Ian in Cumbria]

Thanks for the comments/suggestions. As far as the need to shade up here in the "frozen north", all I can say is that this year I started to get greenback on the toms, painted the south and west sides of the gh with Coolglass? and toms which set later were fine. There is a fence to the East of my gh but the south and west sides are open so it does get lots of sun. I've decided to go with shading outside when necessary, simply because it will be easier to remove if the weather is dull once the toms etc have grown. I'll need to think how to attach it but you have given me some good ideas. I suppose I could use some additional W clips to trap the mesh leaving the existing ones holding the glass untouched.

Anyway, spent some time today emptying the gh (how do the tiny snails get in there?), now need to buy some Jeyes fluid (thought I had some), give it a good clean and think about what to grow next year. Thought I might try Floridity toms alongside the old favourites. Anybody any experience of these - they seem to get good reviews for flavour in a number of places. I'm more interested in flavour than quantity as I suspect most non-commercial growers are!

Regards

Ian