Overnight temperature

I was asked earlier what would be the lowest temperature to leave seedlings/young plants out overnight for hardening off. I hadn't got a clue! I've always gone on my own judgement and weather estimation, taking into consideration late frosts for instance.

Any ideas please?

 

I wouldn't leave any young seedlings out until we get around 10C.

But a lot depends on what it is and how hard it is already.

 

I was thinking on the fact that grass germinates at 12C @pete, but grass is tougher than most plants.

 

Looking at current temperatures it'll be weeks before it even gets over 5C around these parts! I guess an unheated greenhouse may be a smidge warmer though?

 

I've got an unheated greenhouse nFrost and cover young plants below 8C with bubble wrap. I certainly wouldn't put them outside at that temperature. The person that asked me hasn't got a greenhouse and needs to move some outside as soon as possible because of lack of space.

 

Yes I'm itching for more space too. I read in GW magazine last month as a rule 5C and above is needed for germination so surely as a rule plants can survive also with 5C and above - but maybe not thrive haha.

The seedlings I want to put in the greenhouse are onions and leeks, so pretty hardy anyway.

 

Ah its March and we are running out of space ! I move my seedlings out of the house around the end of March to an unheated Greenhouse and shed . If the night temp threatens to go below 5°c I put a small heater on . I would not move them out side until it is touching around 10°c. A sheltered position really does help a lot.

 

I've never hardened anything off before the middle of May, and I've never put anything out permanently before the Spring Bank Holiday Week at the end of May/beginning of June.

 

Hmmm, I certainly wouldn't risk 5C that's almost frost temperature! Plants may survive at that but I don't think seedlings would.

I don't grow veg but I wonder if they are hardier than flowers?

Thanks Harry, you are agreeing with Pete, so I'll recommend 10C expressing caution at this temperature.

 

If that is possible , yes

 

As Anthony said its getting into May when you can get plants outside.

 

Ahh, but this person lives abroad which is why I was going for temperature.

 

That's a good idea then , when they reach around 10 should be OK
Tell them pete said that not me though....

 

I can't do that Harry because I'll then get my ears bashed by my other half.....who is also Pete!