Plastic greenhouse - when to open door?

elsmandino

Hi there.

A keen but very much an amateur gardener, here.

I have bought myself a 5-tier plastic greenhouse and have been using it to grow chilli and tomato plants for the last month or so.

Up to now, I have always left the door closed, with a tray of water at the bottom, for humidity purposes.

The only time I ever open the door is to water my plants at night.

However, I have been reading that this is not always a good idea as plants also need airflow and the temperature, on a sunny day, can actually get too much for plants.

Ultimately, when should I be leaving the door open?

Any pointers would be much appreciated

-taff

Whenever it's sunny and not too windy. They are both self fertile so just give them a light shake or taps when the flowers come.

Your greenhouse is not going to be tall enough for your tomatoes if they aren't hanging basket bush type. And depending on your chillies, it won't be tall enough for them either. Have you factored this in to where they will end up eventually?

twopenny

Both will grow outside but not so early esp chillies.
So temperature wise they don't need it very hot. Can you cobble together something to keep the door open in varying degrees, even a couple of stones?
Then go by the weather, predicted hot then a lot, cold then just ajar.
It's dependent on which part of the country too. Most places should stay mild from here on.

elsmandino

Thanks very much - really helpful.

So the message that is certainly to have at least some airflow in there, whenever a sunny day is forecast?  

My original thought was to buy a thermometer and try and work out how much the greenhouse increases the internal temperature from the outside - e.g. if it increases it by 10 degrees, say, I could add that on to the expected forecast and only open the door if the likely internal temperature is more than the plants could stand.

In reality, I think I am therefore complicating things.

-taff said:

Your greenhouse is not going to be tall enough for your tomatoes if they aren't hanging basket bush type. And depending on your chillies, it won't be tall enough for them either. Have you factored this in to where they will end up eventually?

As you say, there is not much room between the shelves.  I have a patio that I am hoping to keep everything on, once they get took big (should absorb lot of the sun's rays as well).

twopenny said:

Both will grow outside but not so early esp chillies.
So temperature wise they don't need it very hot. Can you cobble together something to keep the door open in varying degrees, even a couple of stones?
Then go by the weather, predicted hot then a lot, cold then just ajar.
It's dependent on which part of the country too. Most places should stay mild from here on.

Great idea - I think I shall see if I can somehow use something in my garden to keep the flap open to different degrees.

I am in the South East, so I usually get some of the warmer weather.

twopenny

Aw hot.
Good idea thermometer. Our local cheap diy store do large ones for a pound.

ArbitraryRandom

I don't think you can just flat say the green house adds x degrees to the forecast.

The forecast temp won't be for the whole day, it'll be the expected maximum at some point of the day (likely but perhaps not just after mid-day), so your greenhouse might never reach that temp - or your microclimate might mean it gets quite a lot hotter.

Ultimately we're talking plants that can (and in a few weeks will have to) live outside, so unless you want to go down the route of buying one of those little temp sensors that can sent a wifi/sms alert to your phone when they get too hot...?

Checking on/watering your plants a couple of times a day on hot days and opening/leaving the door open whenever the weather isn't forecast to be foul will be the easiest option, plus it will start to harden off your sprouts ready for when they need to leave the safety of the greenhouse

Nobbie1967

I’d leave it open all day and close up early evening. The plants will still benefit from a micro climate from being enclosed on three sides. If you leave it closed it will almost certainly get far too hot for the plants inside.