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Cosmos seedlings

Bex2012Bex2012 Posts: 45

So last wednesday evening I sowed some cosmos seedlings in a windowsill propagator... Checking them this evening some of them are already at least 2.5" tall and touching the 'roof' of the propagator.

What should I do with them? There are still some cosmos seeds to germinate in there,  so should I pot on the germinated ones already? Or should I lift them & plant them deeper so they don't flop? I'm growing them in modular cells.



  • Take the lid off the propagator and when they get to 3 or 4 inches tall then pot them on. Be sure to keep the compost damp though when you take the lid off. I usually find some of the seeds are slower to germinate. But when you take the bigger ones out to pot them on you may find you can put the lid back on the propagator to help the smaller seedlings catch up.

  • chickychicky Posts: 10,325

    Hi Bex - this has happened to me before with Cosmos - they go a bit wild!  So I now wait til March to sow, don't give them any heat (just a light windowsill) and prick them out, with quite a lot of the stem below the compost.

    if you want to attempt to rescue the ones you have now, i would try planting them up individually, but you will need to plant them deeply to stop them keeling over.  And keep them off the heatimage

  • Thank you! I was really shocked at the size of them, they aren't even in a heated propagator, just a bog standard windowsill one from Wilkos, AND they aren't even on a windowsill, just my dining table in a mostly unheated conservatory!

    looks like some potting on is on the cards for this weekend then...

  • punkdocpunkdoc Posts: 13,244

    I think that you have sown too early and with not enough light. If I were you I would start again in a few weeks time and start them off on a windowsill. They need lots of light.

    There are ashtrays of emulsion,
    for the fag ends of the aristocracy.

    S.Yorkshire/Derbyshire border
  • Hostafan1Hostafan1 Posts: 33,723

    let them " chill"


  • Wow, lots of advice! I'll pot on the bigger ones to see if I can save any of them, but I'll also start off a new tray - so really slow, steady, and with lots of light is what I'm after? Maybe a bit of cold?

  • LynLyn Posts: 21,373

    Pot them on deeper in separate pots, pick out the tops, pick any flower buds off or they won't do anything at all, then grow another lot at the end of March, without a propagator, Last year I set seeds at the end of May, they lasted well through Autumn.

    You can't plant them out till end of May at least, last year it was first week in June, imagine how big they will be by then.



    Gardening on the wild, windy west side of Dartmoor. 

  • End of March for Cosmos, would that advice be good for up here in Scotland?

  • punkdocpunkdoc Posts: 13,244

    As they cannot go out until after the last frost, you could easily wait til April to sow, especially in Scotland.

    There are ashtrays of emulsion,
    for the fag ends of the aristocracy.

    S.Yorkshire/Derbyshire border
  • Pauly2Pauly2 Posts: 12

    Great question Bex2012, I was wondering what to do with my cosmos. Thanks.

    Lots of info to take in.

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