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Dahlia - getting very big - when can it go outside?

I bought this dahlia as a tuber back in Feb I think. She's doing super well, very happy on my sunny windowsill and growing by the day. As she's taking up sooo much room and I could do with the windowsill space, I was wondering when she could go outside...

I have never had a dahlia before but I understand from google they love the heat and can be quite delicate. The plant is quite tall, so I can't fit her in a coldframe. Would she do OK in this pot in a sunny spot? (I don't have much room in the ground apart from a planter currently full of loomy soil... 

Any advice? 

Thank you!


  • FireFire Posts: 17,116
    edited April 2022
    Hi, what are your night temps doing in Norwich and what are the forecasts for the next two weeks? In London it looks like we have past our last frost dates so dahlias can go out / be hardened off down here as long as we keep a hawk eye on the night temps and take in or fleece if it dips down towards 3 or 4oC.
  • Night temps in Norwich according to BBC weather are between 6 and 7 for the next couple of weeks, with mostly moderate weather (amazingly). 

    OK - what does fleece it mean??? Put fleece on it to protect it from the cold? How would you do that? Just around the root? 

  • FireFire Posts: 17,116
    Horticultural fleece can be used to keep tender plants warm, if you don't have inside space or a greenhouse.  You would wrap the whole plant in the fleece and tie it with wire or string. I should think you wouldn't need it, though, for your dahlia.

  • FireFire Posts: 17,116
    edited April 2022
    GW suggest hardening off dahlias for a week before leaving them outside for the summer. This means leaving the plants outside during the day and bringing them inside at night so they can get used to the very different conditions of the garden and can cope with the big temp drops through the day and might. It helps to stop them going into shock - potentially going into stasis for ages or potentially turning up their toes.

    Keep them well watered.

  • PlantmindedPlantminded Posts: 2,259
    edited April 2022
    I have six plants just a bit smaller than yours and have been putting them out on some sheltered steps next to my house for a few hours each afternoon to get them acclimatised, bringing them back indoors overnight.  It may be safer for you to do this over the next couple of weeks with your dahlia rather than risking rain, wind or frost damaging it overnight while it's still a bit tender.  Then find a permanent home for your plant in early May. (I'm waiting for my tulips to fade before moving in with the dahlias!)
    Wirral. Sandy, free draining soil.
  • Makes sense, thanks!
  • FairygirlFairygirl Posts: 52,034
    Don't forget that frosts can occur at +3 degrees, hence the warning on car dashboards, but it isn't the only problem with putting plants outside when they've been grown indoors. Rough, wet, windy weather does just as much damage. 
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • @Fairygirl
    OK, got it. So basically they're never safe in the UK???
    Seriously though, what do you do when you have plants in the ground and rough windy weather is on its way? 
  • FairygirlFairygirl Posts: 52,034
    It comes down to the plant, and where you site it.  :)
    Anything likely to get damaged by wind would need proper support, and that would go in early on. The amount of shelter in a garden is also important, as well as the plant choices. Putting something into an exposed site, when it's been indoors and has a lot of soft growth is always difficult. The same plant, given support, and the right site, will settle and be fine.
    Once plants are toughened up, and used to the local climate, it's easier for them  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • punkdocpunkdoc Posts: 13,691
    I think the problem was you started it too early.
    In most of the country they cannot go out till the end of May, so if you are growing them inside, there is no point starting them till mid April.
    How can you lie there and think of England
    When you don't even know who's in the team

    S.Yorkshire/Derbyshire border
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