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dahlias in containers - compost advice

REMF33REMF33 Posts: 731
in Garden design
Apologies if this has already been addressed. I have rather more dahlias than I intended to have (bought some for mother's 92nd birthday, but can't visit now, obviously, so just rebought what I had got her to send directly to her, and I have what I bought for her.) I want to put them in containers, as limited space in the ground is already ear-marked. I have googled how to grow them but there seems to be inconsistent advice regarding the growing medium. 
Any advice?
I am currently soaking two tubers in water.

Posts

  • JennyJJennyJ Posts: 10,576
    Are you planning to lift them and store indoors for the winter, or keep them permanently in the container? If the latter, something with "body" like John Innes No.2 or 3 compost. Otherwise I don't think it much matters. Dahlias are hungry plants so they'll probably need feeding after the first month or two anyway. Or you could mix in some slow-release fertiliser granules.
    Doncaster, South Yorkshire. Soil type: sandy, well-drained
  • REMF33REMF33 Posts: 731
    I left last years' in (but put jackets round the pots. No sign of life though yet...)

    Great. Thank you! I have generic 'Multi-Purpose Compost with John Innes'  (Wickes' finest ;) All I ccould get once lockdown and garden stuff panic buying began.) I also have some slow release stuff, thankfully. 

    I shall put a couple out this afternoon.

    Thank you for replying so quickly.
  • Pete.8Pete.8 Posts: 11,340
    I had 2 big pots, some spare Arabian Night dahlia tubers and a spare bag of MPC with JI.
    I planted the tubers in the pots 3 years ago and though there's no sign of them yet, they have performed well over the previous 2 years. I've also just left the pots to overwinter in the garden.
    I do feed them about once every 2 weeks with tomato feed and they do need a lot of water in the summer.

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • REMF33REMF33 Posts: 731
    I had two in containers last year. (But couldn't remember how I planted them up. I have a vague memory of possibly using grit.) Two were gorgeous. One never flowered. I may not have looked after them sufficiently well. More time to lavish attention this summer, I suspect. 12 inch pots? Or is that overkill?

    [I imagine my mother, who is/was an expert gardener (but now chair bound and has a terrible memory) but who has never grown dahlias, has just had them shoved in pots. She says they are coming up (in her sitting room) already. It took about ten conversations for it to sink in that I had sent them to her, and that they were not a free gift from J Parker... Of course it might not be warm enough to grrow them where she is and that's why she hasn't.]
  • Red mapleRed maple Posts: 1,138
    I grew two tubers in pots last year and planted in a general all purpose compost, giving them an all purpose feed (the pellet kind). They did really well. I lifted them to overwinter in the garage and will be repotting them again soon once all risk of frost has gone. Hope that helps.
  • REMF33REMF33 Posts: 731
    It does. Thank you, Red maple.
  • Dirty HarryDirty Harry Posts: 1,048
    MPC and plenty of tomato food once they get flowering.
  • REMF33REMF33 Posts: 731
    Sarah Raven (I watched a video...;) ) puts hers in a polytunnel on heated capillary matting :o I am afraid Hotel Dahlia in these parts is only one star, so they might get a fleecy jacket. I could bring them into the unheated glass-roofed lean to down the side of the house, but it's getting a bit crowded in there.
    Ms Raven put hers in quite small pots. I imagine she was going to plant them out later. I suppose I could do that, then pot them on... although I am a bit short of pots of that size. Maybe I can do some potting on. Generally a bit worried about the pot situation. I have quite a few very big ones, but then there's the compost situation too...
    I potted up a Darling Harbour and a Kelsie Annie Joy. The rest really need to wait for the tulip pots to become vacant which maybe some time... unless I go down the Sarah Raven route and put them in smaller pots indoors. Hmm...
    It was 20 degrees here today. It's hard to imagine that we will get a frost. But you never know.
    I am wondering if the ones that were outside in jackets all winter will have survived. Should I poke around to see if there is any sign of life?
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