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harden off before move to greenhouse?

I am growing various herbs/plants from seed (basil, oregano, pepper, aubergine, tomato) on my windowsill.  I want to move them to the greenhouse as soon as I can.

Do I need to do the 'harden off' step when I am moving into greenhouse or is this only needed when moving them to the garden outside with no protection?


  • Dave MorganDave Morgan Posts: 3,123

    They'll probably be warmer in the GH than on your kitchen windowsill, especially with all the warm weather we're having, so there's no need to harden off.

  • mamehamameha Posts: 40

    Do you think I can put them out overnight in the GH now, no problem with frost etc? (i am down south).

  • PalaisglidePalaisglide Posts: 3,414

    Keep your greenhouse well ventilated during the day and closed up at night. If there is a cold spell warning some fleece draped over the trays will be enough. Once seed is set the need is for light a greenhouse is far better for all round light than a window sill. I often put trays on the floor of the greenhouse at night it will be a few degrees warmer down there, lift them back on the staging during the day.

    Here in the NE, we have had hot days and some cold nights, greenhouse management is a constant job, too hot kills them too cold kills them, sowing little and often is how we do it and a frost guard plus cool air fan helps.

    Hope this helps,


  • mamehamameha Posts: 40

    My GH has an automatic vent (god knows how it works, magic!) so it opens during the day and closes when cold.

    I don't have any power source or fan/heater etc in there, will just rely on the suns power.  

    I will move them all out the GH and reuse the windowsill and seeding trays to do a second sow.  Thanks for advice.

  • PalaisglidePalaisglide Posts: 3,414

    Greenhouse automatic vents work by an expanding gas or viscous oil being heated and pushing a piston up a tube connected to the vent thus pushing it open. As it cools the piston drops back closing the vent. Think of your thermometer rising and falling, stick a rod on the end and you could open anything. Without power then you need to keep a check, my way is open the door and vents early morning, better a bit cool than overheating.

    Your greenhouse should now be warm enough to set most seeds. Put a clear cover over the tray or plastic bag over a pot, as I said above light is more important than heat.


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