Greenhouse question

[Nik]

Hi all,

I'm a fairly new greenhouse owner. It's at my allotment down the road. I'm starting to raise seedlings now, I usually start them on the windowsill and then keep them in a blowaway in the garden and zip them up at night or bring them inside if there's a frost alert. This year I want to put them all in the greenhouse, but I won't be able to bring them in if there's going to be a frost. So my question is, how cold does it need to be outside to kill seedlings inside a greenhouse - and is that really likely to happen between now and summer?

[rustylady]

How long is a piece of string Nik? None of us can predict the weather.

Also depends on what type of seedlings. Things like tomatoes, cucumbers, squash and chillies need much higher temperatures than brassicas or salad leaves.

[Beanz]

If you have an unheated greenhouse the temperature inside will not be much more than that outside after a cold night.


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[Bill HH]

My green house offers about 1 or 2 degrees c over the outside temp, and most of that is due to sheler from the wind, if its going to be cold I drape bubble wrap over things. There are two consequences of low temperature, frost will kill many things, but general low temperatures just above freezing will slow things down almost to a stop. I often think the plants that have gone through this stop start routine turn out poorer than ones you sow a month later that fly away.

[batman]

Chances are, in Cambridgeshire, you'll still have a few nights with frost until end of April or the first weeks of May. An unheated greenhouse doesn't really protect against frost in the air overnight, but keeps the soil a bit warmer (i.e. the soil doesn't freeze as quickly as outside).
This means that hardy seedlings, like brassicas, peas and broadbeans will be fine overnight in the GH, but anything that doesn't do frost (tomatoes, chilis, cucumbers, courgettes, french beans) should be indoors.

[binley100]

I've had toms in my greenhouse for weeks now. But... the gh has bubblewrap round the sides, the pots are sitting in black trays (which absorb heat) and I have fleece draped over them which is supported by plastic milk bottles filled with water .They heat up during the day and release the heat slowly through the night, a bit like hot water bottles.... So far so good .

[dod]

I had tomatoes and peppers in a greenhouse very early (beginning of April) a couple of years ago, I don't think there was quite a frost in there, but it was fairly close a few times. None of them died (I think some cucumbers did though), but they were desperately slow to get going. I suspect putting larger plants (grown indoors on a windowsill) out a bit later would make quite a difference. I tend to keep them inside much longer now, but don't have the distance issue you do.

[Newishgardener]

Surely to answer this question more information is required it depends on what seeds are being sown and the individual temp ranges of each seedling if it's peas and cabbages that have been started off I would assume they should be ok but if it's tomatoes or chillies and things like that then no lol I'm fairly new too so I am going by what I have read.


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[MartinRSharpe]

I put a cheap paraffin heater in the greenhouse and just light it up at night and turned off in the morning (when i remember). It has kept the temperatures at or above 10C for the last few weeks.

I got though about 2-3L of paraffin in a year.

Tender plants inside the greenhouse are also in the basic propagators which also gives them a little bit of extra protection.

[Nik]

I think I'll be patching up the blowaway then - it's full of holes! Cheers guys.

[Two_Sheds]

to answer this question ... it depends on what seeds are being sown and the individual temp ranges of each seedling

Quite right: different plants have different requirements. Up to now I've only been putting hardy seedlings in the gh (my last frost is late April). I'll be starting tender (half hardy) seeds soon, in the little heated prop. They'll be moved to the gh in a few weeks, which will be just about mid-April. I can grow everything well in that timeframe without the use of gh heating fuel