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Moving seedlings to an unheated greenhouse

I have seedlings on a sunny windowsill that are approximately 2"-3" tall, a mixture of dahlia, cosmos, chilli. I also have an unheated greenhouse. When should I move the seedlings to the greenhouse? (I live in the south east)


  • AnniDAnniD Posts: 11,158
    Do you have any fleece that you can use for protection overnight? 
    If not, you could keep them in the greenhouse during the day and bring them back in overnight until things warm up a bit.
  • I do have some fleece that I could use. Do you know what night time temperature I should be wary of until I stop using the fleece?
  • Mary370Mary370 Posts: 2,003
    Usually when temps reach  double figures.....
  • AnniDAnniD Posts: 11,158
    If it heads anywhere near freezing definitely use it. I err on the side of caution and if it's around 3 degrees or less overnight, that's when l use it.
    You may find a maximum/ minimum thermometer useful, and l also have a  gizmo in the lounge that has a warning light if the temperature in the greenhouse drops to 2 degrees C or below. 
    I daresay there's an app somewhere as well  :)
  • ObelixxObelixx Posts: 28,804
    Chilli seedlings won't be happy going below 10C.  A more mature plant could cope a bit cooler but not babies which will be checked or killed off.

    Dahlias and cosmos are hardier but seedlings won't be happy below 5 to 10C I shouldn't think.
    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • REMF33REMF33 Posts: 641
    Does this advise apply to all seedlings? I am finding that my greenhouse is sometimes actually colder than outside, at the moment, at night. (Thermometers are stationed in various places!) I have quite a few hardy annuals (as well as HHA and stupidly big tomatoes sown too early because I am new to greenhouse gardening and thought I would be able to put things in there before I'd normally put them outside...) and was wondering if they, at least, could go in it as I am running out of room indoors. I can gain an extra degree of two, I suppose, by putting them in an unheated propagator inside the greenhouse.
    The night time temperatures always seem to be colder than the ones the Met Office/BBC suggest for my area when I type in my post code so it's hard to predict. I am in SE London.
  • AnniDAnniD Posts: 11,158
    @REMF33 ,C an't say about the tomatoes, but the others should be okay. I'm in the South West and have HHAs in the greenhouse having just pricked them out. I do add fleece over them if the temperature drops to around freezing at this time of year. It doesn't hurt to err on the side of caution as long as you take it off in the morning. Temperatures can rocket in a greenhouse even at this time of year.
  • philippasmith2philippasmith2 Posts: 2,639
    Coastal SW UK here and I currently have the following seedlings/small plants in the unheated GH..........Peas, Beans, Cucumbers, Tomatoes, Peppers, Courgette and Basil.
    I always fleece at the moment whatever the forecast.  Even those seedlings which have only recently germinated ( in a heated propagator ) benefit from the light ( and sun if we are lucky ) as the only place for my propagator is by a North facing window.
    The cool night temps may well set back growth somewhat but they will soon catch up as the days lengthen. 
    It really does depend on your location as to whether you go for heat or light with seedlings. 
  • REMF33REMF33 Posts: 641
    edited April 2022
    I have grow lights. It's more a question of room. Hmm. I suppose it's early enough that if I lose some, I can sow more. I might just experiment with a few. I did put some beetroot in there as they are so etiolated they may need ditching. (I only have so many grow lights...) Too cold in mine for med veg and half hardies, I think.
    I am going to have to try and off load lots of tomato plants this weekend if I am well enough. (Day 6 Covid and still very weak... but itching to do some gardening, albeit of the sitting down variety.)
  • Nanny BeachNanny Beach Posts: 8,343
    Also in the SE. You say "unheated" green house,if you're lucky it might be frost free. I wouldn't put a 2 inch tall seedling in a green house. My top green house,is double glazed with thick bubble wrap, more goes over the plants at night, plus a tubular heater. That counts as a cold green house. I use it for overwintering. Seedling your size have just come from the kitchen window sill,into the conservatory, now need potting on. Another month they will go into a small lean-to green house.
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