[hubballi]

Having only just got my lean to greenhouse I am not sure about what temperature it should be. For instance, before I opened any window and door this morning in full sun it was showing 40oC. I have salad, peas, b beans, spuds, beetroot etc growing. The greenhouse is south facing. I open the roof vent and door and it gets down to around 25 oC but as soon as the cloud comes the temp drops so I have to be careful.

[azubah]

I have the same problem.
My greenhouse is partly shaded by the house, but it still got up to 100F. Sorry, I still work in degrees F at these temperatures.
Tomatoes do not like it over 80F, and droop, I find, so I leave the door open and hope it does not get too cold when I am not around.

25C sounds a healthy temperature to me.

to convert from f to c subtract 32  and multiply the result by 5 and then divide by 9

[stompy]

Get yourself an auto vent opener.
Takes all the hastle out of it, and it's name sugests, it does it automaticaly 

[mumofstig]

they're not so easy to fit in a polycarb greenhouse though, and that's what hubballi has, I believe  


Unless a cold frosty night is forecast I leave the window open an inch or two.

[hubballi]

I can't get it any lower than 35 0c with the door and window open. The trouble is if I leave the window open at night slugs and snails will get in.

[Gandan57]

You also need to think about some method of shading.

When I had a greenhouse I used coolglass paint on shading. Cheap and easy to aply.

[hubballi]

I have a white polythene sheet as well as some spare wooden slats from a venetian blind.

[Kristen]

Those seem like scary temperatures to me for this time of year.  Plants will be having to cope with high day temperatures, followed by much lower temperatures during the night (which is a bit different to hot temperatures in the middle of Summer when the night temperatures are also warm).

My conservatory doesn't get much above 20C - 25C / 68 - 77F this time of year (if I forget to open anything). I think its probably an issue of size - small greenhouses / conservatories are much more difficult to temperature control that larger ones.

My suggestion would eb to try to keep them below 25C during the day, and no less than 10C at night.

[hubballi]

It's on a white painted brick wall in a small and sheltered walled garden. There is no breeze at the moment either. Just put a white polythene sheet over the top in the hope to bring it down.

I never seem to have any luck do I. I have been years wanting a greenhouse and when I get one it's too hot and it's in NW England in March !!

Do you think the damage has already been done to my plants/seedlings ?

[hubballi]

I can't keep up with this. It's been around 10oC most of today and then the sun comes out and it's nearly 30oC. I open the door and window and the sun goes in and it's too cold.

How am I supposed to keep up with this (and don't say automatic vent as I can't afford the high price of one)

[Carrotcake]

I think shading is your only chance. I had fine green netting on the sunny side of my greenhouse which made a huge difference at this time of year. I think polythene may actually be adding to the problem 

[mumofstig]

From your list of crops in the 1st post, there is nothing there that would suffer any harm with the door open. (they could all be outside in fact )

Put some slug pellets in there if you are worried about the pests. When do you think you will be planting things out?

[hubballi]

I can't plant anything out yet as the garden is all in bits as I am trying to work out a new design. Will have to grow in containers for now.

[hubballi]

I have had it with this hot period. Ruined a few crops (cabbage, Radish,spicy salad) and everything dries out within a short time after watering. Despite having the door, window open as well as white sacking for shading it's at 37oC and we are only in April. Whatever it will be like in high summer I dread to think.

Thanks for the advice of putting it south facing here 

[mumofstig]

We are all in the same boat with seedlings, you could have moved them to a shady spot in the garden during the day, and back into the g/house at night.
To have these temperatures in March is, you must admit, very unusual!

When it is this hot in the summer, the crops inside the g/house are usually the ones that love the warmth

So please blame the unseasonal weather, and not the people who offered you advice.