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I built a large propagator to overwinter plants and use next year to harden off.

i occasionally open the lids if weather permits. 

Today I lifted a few things around in there and found a lot of mould beneath the pots and trays.

the lids are wooden frames with something a bit more substantial than fleece. More nylon I would say but not too thick. Has this happened because there is a lack of ventilation? everything is sitting on a good layer of grit. 

i gave it a good rake and left the plants out all day but they're back in now. Will the plants be okay and can I prevent this by more ventilation or moving everything around. I would have thought the materials I have used would have been ideal to let water through and help ventilation. Jings, crivvens, he'll ma boab.   far too many plants in there too loose.



  • Hi Heather, can you describe or take a photo of the mould?  Without knowing exactly what it is, it's difficult to advise.  Removing all of the plants and watering the gravel with diluted Jeyes Fluid might help if it's some form of fungus but probably not if it's an algae like Nostoc commune.


    A trowel in the hand is worth a thousand lost under a bush.
  • Too late, I raked it in through the grit. I will take all the plants out tomorrow again and give it a good raking and airing again. The soil in the pots was saturated.

    i should have said it was a cold frame and not propagator.

    i will google both your suggestions and see if I can locate something similar. Thanks

    not great at putting pictures up on the forum. image


  • LynLyn Posts: 21,346

    I think you have said it yourself 'pots are saturated' plants in coldframes this time of year should be almost dry, the more water in them, the more chance they will freeze solid.

    Could you put them somewhere else, greenhouse? Until they dry out.

    Gardening on the wild, windy west side of Dartmoor. 

  • Dave MorganDave Morgan Posts: 3,123

    heather, mould only grows when its too warm. Cool it down, kill the mould spores as Lyn has said and increase the ventilation.

  • bad ventilation and pots with  water in or leaks gives mould a good place to grow . empty any water filled pots and don't water to often (they don't need it ,the plants)

  • I cannot think of a time when I've ever had my cold frames totally closed.

    “I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh

  • Thank you everyone, there are three lids that cover one cold frame and I plan to re-cover two with polythene. Keep one with mesh for ventilation. We are very exposed here so the wind would cause damage if I was leaving the cold frames open. 

    i think the mould under the pots were from the slug pellets I put down before I put the pots in. image

    You learn something new every day. Especially from you guys on the forum. 

  • Can anyone help me with mould developing on the leaves of my Camellia cuttings in my new Propagator?  It is a Stewarts and cannot be heat controlled manually.

    The vents are fully open, but the lid condenses up still.

  • YviestevieYviestevie Posts: 6,959

    No expert rose but maybe try taking the lid off.  Ive taken quite a few cuttings for the first time this and have not covered them and so far they seem to have taken.  That said they are in a cold greenhouse.  Hopefully someone more qualified will come along and help.

    Hi from Kingswinford in the West Midlands
  • FairygirlFairygirl Posts: 50,236

    Mould usually develops where there isn't enough ventilation. Do you have the propagator inside the house as well? As Yvie says - if they're in a greenhouse or even indoors on a windowsill they shouldn't need any extra help. I definitely wouldn't have heat under them, just shelter from the cold weather.  image

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

    I live in west central Scotland - not where that photo is...
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