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Tomato Seedlings + Cold Nights

Good Morning!
My tomato seedlings that I sowed on the 20th have put on good growth and are ready to be lifted out of my heated propagator and potted on into small pots. However I was thinking with our cold nights will they be okay sat on the GH shelves?
I do have bubblewrap protection and a heater that is set to come on if the temp drops below 4c ... however I don't completely trust this heater. Will the seedlings that I potted on be okay overnight sat on the greenhouse staging as looking at the weather ahead the temp drops to 1c each night, or am I best lowering the heat in the Propagator and popping them back in? I just wondered what you folks would do image 


  • chickychicky SurreyPosts: 9,702

    I find that tomato seedlings really suffer if they get hit by frost.  Mine normally go out into an unheated GH in April, and I spend the evenings covering them with fleece and the mornings uncovering them if cold is forecast.  They are with all my other (mostly flower) seedlings - but are always the first to show signs of stress .....they turn a sort of purpley blue and stop growingimage. Don't normally recover either, so have had to resort to GC replacements.  So.....I would keep them somewhere you are confident will be frost free.

    We did not inherit the earth from our grandparents.  We’re borrowing it from our children.
  • emma louemma lou Posts: 159

    Thanks. These are indoor seedlings and could be a light issue. I have just repotted them into deeper trays and will try leaving them in sunlight during the day and see what happens. I could not split them as they are so spindly and was hard just trying to repot them into 3s from their original seedling trays. A couple more weeks should make them stronger. They are just at a vulnerable time I think and should strengthen up with more sunshine and the repotting. I so desperately need a greenhouse but even at the moment without a heater they wouldn't survive long in there either!

  • FairygirlFairygirl west central ScotlandPosts: 36,891

    It's why I don't sow until well into March. I remember Italophile saying they need a minimum of 10 degrees overnight. You'd need your greenhouse reliably and consistently warm NG. It's fluctuating temps which do the damage. 

    We only get a short spell of that in summer which is why I have to have them undercover the whole time. image

    It's a place where beautiful isn't enough of a word....

  • To be fair I didn't expect them to be ready for another week or so lol I could always set the Propagator to 10c overnight :/ 

  • ItalophileItalophile Posts: 1,730

    If the seedlings are ready to be potted up, don't put them back into the propagator. If they're already lanky, they will only become more so without bright, consistent light. Pot them up if they're ready, put them into a low-sided crate - the sort you get from a greengrocer or garden centre with plants in - and wrap the whole crate in bubble wrap. Put the crate in a protected, sunny spot. The bubble wrap will help to insulate against the cold and you'll be surprised how much warmth it will trap from the sunlight. Take the crate inside at night.

  • mac12mac12 Posts: 50

    I have  a cold frame in my greenhouse for cucumbers that I put seedlings in, the extra glass is just enough to keep things warm when its cold outside. You have to be careful they don't get to hot sometimes during sunny days.

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