Questions about my Dahlia tubers!

wakeshinewakeshine Posts: 950





Hi everybody!

I am new to gardening and got carried away. I have a lot of flowers growing at the moment. I did not even realised Dahlias weren't perennial. When I saw them on sale in March I bought several bags, as they were quite cheap in Morrisons and Home Bargains! I thought it would be a simple case of putting them in the ground, but it has been too cold. Then I learned that it's best to grow Dahlia tubers inside. So I had a total of 25 tubers and potted them into medium and large size pots. Only a couple of them haven't started shooting yet. Various questions:

Do you think they will come up? Are they just still asleep? Is there a chance I could have put the tuber upside down?

Also, here are some photos of the pots in my growhouse. Another question - is the first one dying or dead? It had proper leaves at one point. I put it outside as I was running out of space inside, and I am wondering if the cold has killed him?

Another question - I was wondering why all the shoots are at thw side of the pots. Should I have used shallow but wide pots instead? Do tubers grow roots down aswell or is all from the top such that I could have put them in a shallow tray and not wasted so much compost? It was a lot of work potting them all into individual pots and a lot of guesswork as to which way to lay them down. Please let me know your thoughts and advice so I can learn for next time what to do. Advice I read online was all different! The next job is putting them in the soil. I may have questions about that too!!

Thank you in advance image



  • JerryBoneJerryBone Posts: 91


    The first picture is definitely damaged by the cold, however it should hopefully come back to health if it hasn't been damaged too badly.

    Some Dahlias may take longer than others to come up, I guess patience will tell.

    Its better to use more soil than just a shallow trey, as they may need to be protected for a little while from the frost depending on where you are located.

    You seem to be doing great, the key to gardening is trial and error, things that work for one person, may not work for others.

  • Dave MorganDave Morgan Posts: 3,123

    From looking at the picture's the top dahlia shoot has died, the ones in your second picture look fine. I'd hazard a guess you've planted them on their side. Dahlias like a roomy pot, 12 inch pots are the usual for more mature tubers, which can be large, but smaller pots are OK, just as long as you can bury the tubers with compost. Some of what bought mightt have withered or failed, dahlia tubers need to be firm to grow well. Soaking newly bought tubers can help with this. Sometimes what you buy will be duff. If you use the search box and search dahlia planting, there's a short tutorial there on correct planting. It should give you an idea if you've gone wrong, not that it matters. You must have done something right to get growth so don't be disappointed. There is a lot more to tell, but watch the video see if you've gone wrong as that may be the root of your problems.

  • Rosemary51Rosemary51 Posts: 7

    I grow loads of dahlias and the top one looks to me as if it mights have been eaten by slugs.  They love dahlias.  The others look fine and just need growing on and hardening off over the next couple of weeks and then planted in a sunny position in the garden.  Slugs will eat them if you don't protect them.  I make a collar out of old cereal packets cut in strips and covered in copper tape and put these round each one.  I find this helps a lot.  Once they have got going they seem to be able to cope with the odd nibble.  Hope this helps.

  • wakeshinewakeshine Posts: 950






    Thank you everyone! Jerrybone thanks for the encouragement too! So far almost everything I have planted seems to be growing. I have several rose projects too which I will make separate threads for my questions.

    Dave Morgan, I got so confused watching videos and reading articles. Can you recommend the correct one? In one video the lady said lay them in a shallow tray but this didn't seem right. In another they were planted in big pots and it said only put soil half way (why?). In an article on web it said don't put tuber sideways, put it vertical. So I put them sideways as this what the majority of articles seemed to say. Will the fact that they are growing very tightly to the side of the pots restrict it in anyway? Do I need to rush now to put them in the ground so they have more space?

    Also with tubers - each one was a group of several. I planted them together. Is this one plant? Will shoots come out of all tubers? Was I supposed to separate them? Photos of what I did above! Please comment, I would be most grateful to know if I did the right thing.

    Rosemary, was the collar put all round the bottom of the plant? Does it have to have copper tape? Do the slugs eat the whole dahlia? Come to think of it I have seem some silvery lines on the patio which could be slugs. I have some pellets, shall I put those around? I have moved my dahlias back to the growhouse now, except for three heavy pots sitting on patio which won't fit in the growhouse. I better bring them in. !!


  • LynLyn DevonPosts: 15,245

    In your picture on the newspaper, where you see the tubers all hanging from a central point, that is the top, you should see a little bit of stalk at the top. This goes just below the compost level, it will only shoot out from around there, it's no good planting just a bulbous bit, it won't grow.

    so you can now see why you need a fairly big  pot, because those tubers should hang downwards, they need to be covered in compost. Those thin fibre type  threads are the roots, so these go downwards.

    dont plant them out until they have grown into big plants, which should be around the end of May, they stand a better chance of not getting slug chewed. I have never used copper tape, but do use a very few slug pellets when first planted out.


    Gardening on the wild, windy west side of Dartmoor. 

  • Rosemary51Rosemary51 Posts: 7

    Plant the plants out and put the copper ring round the base on the soil.  The copper repels the slugs.  They don't like it.  Copper tape is readily available at garden centres.  I do not use slug pellets as I have toads and hedgehogs in my garden.  You will know if you have slugs as there will be slime on the leaves and the shoots will be eaten.

  • RainbowfishRainbowfish Posts: 276

    I am trying a few dahlias this year too. Mine look very much the same. I was hoping they wouldn't start shooting for another couple of weeks. I have them in the shed & chocolate cosmos on my windowslil with chillies & cucumbers.

    They are perennials. You can dig them up to overwinter them in a frost free place.

    I was going to try my Mum's method of forgetting about them. Frost kills the leaves & stems every winter but apparently her garden is mild enough that even in the really cold winters a few year back, they still came back up in the spring bigger & better.

  • wakeshinewakeshine Posts: 950

    Thanks Rosemary I will try that. I have put the pots on a table outside for now so the slugs can't get to them. I might try the copper ring, thanks. Will slug pellets work also? I can scatter some around the plant when I've put them in the ground?

    Rainbowfish, isn't the shed too dark for them? Are they growing yet? That's cool if they are, next year I can try the shed too. My mum planted a dahlia last year too, and also didn't dig it up over winter because she forgot exactly where it was. We looked today and it looks like it might be coming up as I saw a shoot and it's not one I planted. I didn't see it last year but if it comes I will ask her if it's bigger! I think I got some Unwins, Pom Poms, Fireworks and Crazy Love. Good love with yours and Chocolate Cosmos!

  • Dave MorganDave Morgan Posts: 3,123

    Wakeshine, Lyn has given you a good guide on which way up they should be planted, fat bits(tubers) down, hollw stalk at the top, where they all join is called the neck and that's where they sprout from. They should hang down in a bunch if you hold the neck. You only want those attached to the neck anything else discard. The method of laying in a tray is only used when propagating early growth for cuttings. Planting vertically is normal when you're just growing them to put in the garden.

  • LynLyn DevonPosts: 15,245

    At this time of the month they should be about 6 to 8" inches tall,and nice and bushy,  ready to go out at the end of the month. By then they will be thick and strong enough to survive a bit of slug chewing if you don't want to use pellets.

    if you do, you only need to put down about four pellets. Hedgehogs don't like slugs anyway, and nothing will eat a dead one.

    If you've left dahlias in the ground, they will only just, if at all starting to shoot now. Well, mine are hardly showing yet.image

    Gardening on the wild, windy west side of Dartmoor. 

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