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Why frost-blacken dahlias?

RedSquirrel19RedSquirrel19 Posts: 21
in Problem solving
Please could someone tell me the biological reason for the advice to lift dahlias after they've been blackened by a first frost?

Mainly because I'm curious, but also would like to lift & store some from a container - so can plant bulbs - and there's not been a frost yet; does it matter? Thanks

Posts

  • Hostafan1Hostafan1 Posts: 34,889
    the first frost triggers them into a plant type of hiberantion.
    If you lift them earlier, and move them into a warm greenhouse, they'll just keep growing. 
    Devon.
  • RedSquirrel19RedSquirrel19 Posts: 21
    Thank you. What if you lift before frost and put in cold place (eg outdoor shed), rather than warm greenhouse; still risky?
  • DovefromaboveDovefromabove Posts: 88,147
    edited November 2021
    In your situation I'd lift them and pop them into a suitable sized plastic pot and leave them out until the frost has done it's job ... no need to repot properly, just lift them out of one pot and into another  :)

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • JennyJJennyJ Posts: 10,576
    They also carry on flowering until they get frosted (if you keep up the deadheading), so it's a shame to cut them down before then.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • FairygirlFairygirl Posts: 55,117
    If you have to lift them [because you're altering a bed or need the space for other plants or similar] - there's nothing to stop you as such, but they're best left in situ for the reasons described.  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • FireFire Posts: 19,096
    Also, if they carry on growing, the tubers will continue to get larger for next year.
  • ButtercupdaysButtercupdays Posts: 4,546
    Mine have had their first frost already! It was shortlived though, but their leaves are a bit black and crispy.
    At 11.30pm on Thursday I had to go out to collect daughter's partner from work and the windscreen was covered in thick rime, needed scraping.  When I took the bin bags out before nine on Friday, everything was wet and clammy. High pressure gave way to low :)
  • bertrand-mabelbertrand-mabel Posts: 2,697
    Well! After so many years in my childhood working with my father lifting and storing them I did the same when we moved into our home.
    Disaster and very upsetting.
    What do I do now?
    Leave them in the ground. They come back each year and more come back.
    Maybe not as robust as they could do but they still flower.
  • UffUff Posts: 3,199
    JennyJ said:
    They also carry on flowering until they get frosted (if you keep up the deadheading), so it's a shame to cut them down before then.
    I agree with you JennyJ. Winter seems a long season so to keep them as long as possible if they are still flowering still brings welcome colour. 
    SW SCOTLAND but born in Derbyshire
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