[Brassica Blaz]

hi everyone,calling on all you experienced greenhouse growers for some advice.tis my first season with a green house and all is going well but i'm unsure wether to leave the door open in the day time or not .i know it gets really hot in the day but i dont want to risk getting  blight or white fly or other nasties.but can to much heat be just as bad?i have an autovent and a louvre door.any advice gratefully recieved.

[Elcie]

I have had the windows and door open for the last few days in this heat as it can get pretty hot in there.  For example at 8am this morning it was 25C in there, and that was in the shade!

Obviously by opening the door you also open yourself up to the dangers of pests/disease, but not much more than that offered by the open windows.  Having said that, if your plants don't wilt during the day with the door closed then they are obviously coping ok with the heat!  Some of mine are still in relatively small pots, and will stay in them, so they need extra watering and ventilation.

[aelf]

yes, open for me too. I feel that it is good to have a free flow of air through the greenhouse to limit the buildup of moulds. Also stops the plants getting too hot.

[mumofstig]

door and window open daytime, and a window open at night 

Blight can get in through open windows..........but you stand more chance of avoiding it IMO if your plants are not kept in the humid conditions which it thrives on. If you plant enough french marigolds in the greenhouse the whitefly tend to avoid it 

[Brassica Blaz]

thanks for the advice,i have toms and cues in there but some one told me you shouldn't grow them together,then i heard that some people wet the greenhouse floor(which ive done a couple of times).i'm a bit unsure now,will the cues cope better with out the humidity,than the toms with.if that makes sense?

[tosca100]

thanks for the advice,i have toms and cues in there but some one told me you shouldn't grow them together,then i heard that some people wet the greenhouse floor(which ive done a couple of times).i'm a bit unsure now,will the cues cope better with out the humidity,than the toms with.if that makes sense?

In the real world we don't all have the space or luxury of two greenhouses! They will do ok, but depending on conditions, one will do better than the other I guess.

[barbarella]

I definitely leave mine open.  I was working in mine yesterday with both roof vents and both louvres open, plus double doors wide open and shade netting up and it was still nearly 35 degrees.  I also wet the floor in front of the cucumbers on hot days, whenever I am about and there is no sign of red spider mite yet.  I am in my first full year with a greenhouse as well, so we are both on a learning curve.

Another advantage of leaving the doors open is that pollinating insects can get in.  I am growing aubergines for the first time and I may put them out on the patio when they are in flower, but even if I don't they will still have a better chance of pollination with the doors open.

Last year the blight struck here at the end of July - it was very warm, wet and humid.  I had just got the greenhouse and was moving in my tomatoes when I spotted the first signs.  I immediately sprayed with Dithane and removed the affected leaves and luckily the crop was saved.  I think I might spray early this year before too much fruit has set as I don't like the idea of eating tomatoes which have been sprayed.  I will also watch the weather and register with www.blightwatch.co.uk - they notify you of Smith Periods (weather conditions when blight can occur).  Then I will keep the doors closed and keep my fingers crossed

[Terrier]

Apart from all the other reasons given here, plants such as tomatoes need an optimum temperature to 'set' the fruits in the flowers. I would think that it would get far too hot in an unventilated greenhouse and you may end up with very few tomatoes on the plants. Some people use electric fans to keep the air moving or louvres set near to ground level. If there are blight spores around, they won't respect closed doors or windows and as Mumofstig says, it's the humid conditions the spores need.

[boosh]

I leave the door and window open on my poly/greenhouse all day and night. a fellow plot holder was opening it up for me in the mornings and said that the heat  was unbearable in there at 9.30 in the morn.
so open it stays, 

[Babstreefern]

I have my window open wide, and my door open wide all day, and then I shut the door at night with just a hand's width opening.  If it goes really chilly at night, I then shut the door, but keep the window open.

[Lardman]

I left the door open on mine the other night - next doors cat had a field day  Just something else to think about, you never know what will get in at night.

[Goosegirl]

In the hot weather we've had lately, my louvre window has been open day and night, also both greenhouse doors. I have a blackcurrant bush just outside the greenhouse which is covered with whitefly, yet there is none on my toms - I always plant about 5 tagetes plants around the 3 toms I grow and never have whitefly in there. When it gets really hot, I dampen down the gravel flooring at least once a day to reduce the heat. Some people use "Coolglass" on the glass panes to prevent the sun's heat being conducted through the glass but I've always found it a swine to remove completely. Last year I didn't use it and still had good tom plants and fruit.

[barbarella]

I left the door open on mine the other night - next doors cat had a field day  Just something else to think about, you never know what will get in at night.

I get the odd paw print in my seedtrays but as we have three cats I have no-one to blame but myself

I can't be doing with Coolglass either.  Shade netting is much better and I've got it so I can put it up and down in a few moments.  See my recent  post with photos - http://chat.allotment-garden.org/index.php?topic=57286.msg682902#msg682902

[DavidT]

Rather than use shade netting, use bubble insulation. This not only  helps keep the greenhouse frostfree in winter, but acts as shading in summer.

[Elcie]

I left the door open on mine the other night - next doors cat had a field day  Just something else to think about, you never know what will get in at night.

Ooh I would be so cross if that happened.  The more I enjoy gardening the less I like cats.  They seem to be the only pet that you don't seem to have to have any responsibility for as an owner.  If my dog/chickens got into someone's greenhouse and wrecked it I would have to answer for it, but not, apparently, cat owners 

I honestly hadn't thought of that so will make sure that it is the window that is left open at night rather than the door if it gets paticularly warm.