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Starting off Dahlia tubers

I am trying to start off dahlia tubers and have them sitting in trays on top of damp compost in an unheated greenhouse.

They've been there for a month and I thought they'd have shooted by now.

Can anybody tell me what I'm doing wrong ?

Any suggestions would be appreciated.




  • Alina WAlina W Posts: 1,445

    Try burying them slightly, so that the tubers are covered - they may not be re-hydrating enough.

  • Chloe2Chloe2 Posts: 5

    Hi Chris, I start mine off in March in terracotta pots in the garage. Planted quite deeply in damp compost. Usually they are fine for planting out in June.

  • Tee GeeTee Gee Posts: 32

    I am looking for clues

    You say you have them sitting in trays on top of damp compost in an unheated greenhouse.

    Are they new tubers or tubers you have saved through the winter?

    If new! then it might be too cold for them and it all depends on how damp is 'damp'!  If they are too damp this can make things cooler still, I have an expression to describe this and that is they want to be the damp side of dry if that makes sense!

    If they are saved tubers how did you keep them through the winter?

    They've been there for a month and I thought they'd have shooted by now.

    I would have thought so too!

    There are some pictures here on how I do it;

  • ive left mine on top of my kitchen cupboards in an old fruit tray. they have started to shoot. the trick i was told by my father in law. is to dry them out thoroughly and slow introduce them to warmer outside temp. or as i have done in your kitchen. damp soil and cold temps wont allow them to start. they may still even rot.

  • I pot mine up in the house and keep the compost just moist and I generally get enough shoots to take a few cuttings.  The ones I left in the greenhouse sadly turned to mush.  Give the tubers a squeeze and make sure they're still firm and if they are, pot them up and move them somewhere a bit warmer.


  • Chris 7Chris 7 Posts: 102

    Many thanks for all your help.

    Ive had to remove a few tubers which are rotten,  but the majority are fine.  I think that the shed (where I keep them) is currently too cold during the night.  I'll move them inside the house (My wife won't like it though !)


  • I have sown some dahlia seed and bought some nice plump firm tubers. I am going to sow more seed in a week or so (kitchen windowsill job) I may plant the tubers at the same time (do you always leave the top of the tuber poking out of the soil?). I may even try some cuttings aswell (going to have to be brave). 

  • SwissSueSwissSue Posts: 1,447

    What is the point of taking dahlia cuttings? The tubers that I dug up last year are so big that I can divide them into 3-4 clumps, each with at least one shoot. That alone gives me so many plants that I don't have room for them all. Not criticising, just wondering?

  • sotongeoffsotongeoff Posts: 9,802

    Some dahlia tubers aren't that big and will not divide and then some people are reluctant to do the chop-perhaps the cutting route is the safer option??

  • ObelixxObelixx Posts: 29,631

    If you're buying new, like me, and want to increase your stock rather than pay for lots of tubers, taking cuttings is an excellent option.   

    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
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