What am I doing wrong? Dahlia advice needed please!

I'm a new gardener and am trying to grow dahlias, my favourite flowers, for the first time. All of the dahlias that I've purchased as young plants are absolutely beautiful (though not very tall) and I'm thrilled with them.

My problem is that every single one I've tried to grow from a bulb is an absolute disaster! I've tried four lots of bulbs, all bought from different places. I started the first three in a nice warm sunny spot on the kitchen windowsill and the fourth in my new pop-up greenhouse.

The first rotted away really quickly, the second I barely watered and checked all the time to make sure they weren't too wet, but they fell apart too. The third I haven't really watered (a little bit of mist!), have been keeping them warm and giving them plenty of light, but, again, no real signs of life except a few tiny roots starting to shoot out over the last few days... and that's after weeks and weeks of encouragement. I planted them with a bit of Rootgrow so I don't know if that's helped. The fourth I haven't watered at all and had no growth whatsoever (but it still looks like its falling apart).

I'm so frustrated. Could anyone please give me some advice? Thank you!

 

They sound too wet. Mine were started in a greenhouse on a heated mat or in direct sunlight just chucked in old compost or left on a tray. I didn't water at all til I saw shoots as there was moisture in the compost anyway. Sorry to hear about your disappointment, if you're local to Coventry I have a dahlia or two you can have.

 

@BrandNewGardener , I tend to kill all tubers and bulbs, so your not alone....even Dafs come up blind. Give me some seeds any day, they seemed to always work, I have grown some lovely Dahlias from seed , and they have bloomed non-stop all summer . These are last years

 

I'm new to gardening, I just put mine in the garden they come up and flower every year even though I planted them north facing ,

I agree with John there too hot, cant you plant them outside ?

 

@CharlieBot Thank you so much, that's such a lovely offer! I'm too far away, sadly. I used to live in Coventry though. I will persevere then and will hold off watering for now!

Thank you, @JWK . Fingers crossed there's hope for at least one of them. I'll definitely experiment planting some straight into beds once the threat of frosts are over next year and see if they do better.

Wow @Upsydaisy , they are stunning! Haha, I'm almost glad it's not just me (sorry!). I've tried growing things from seeds and they seem to be doing really well so I think I'll have to give that a go too.

@martin-f I'll try that instead. The poor plants, I thought I was giving them a boost by keeping them warm. I've only got one left that I think still has even any slight sign of life so I could put that in a bed, but it would get quite wet next to the other plants so should I wait until it's starting to sprout before I move it to stop it rotting?

Thanks again, I really appreciate all of the advice!

 

Hi BrandNewGardener. I am not sure what your problem is, but as Dahlias come from Mexico and Costa Rica, I would be surprised if it was too hot for them.

Overwatering is often the reason why tubers and rhizomes rot. The purpose of watering is that the water is sucked up through the roots and provided to the leaves to replace the water lost by transpiration. However until a plant has roots and leaves it can't use any water at all. So its quite acceptable to not water it until it has some decent leaves. I like to use a moisture meter for many plants, as the surface of the compost can dry out, but a couple of inches down it still can be very wet.

The recommended way of starting Dahlias off is to lay them on a tray of slightly damp compost, only half covered, and to leave the woody crown at the top completely uncovered. Its the woody crown that rots first rather than the tubers themselves. Once the leaves appear, you can repot it normally and start watering.

 

Sorry Peter what I was meaning was they need to be a certain temperature to sprout, keeping them indoors at more/less a constant temperature could cause a sprouting issue,

They don't appear to be a plant that needs any encouragement to grow, mine get hardly any water or sun and the come up every year and flower lovely.

 

Hi Martin. As I said I don't really know. I have always left them in the sun spread out on top of a tray of compost, having spoken to members of the National Dahlia Society who usually have a stand at the Harrogate Flower Show.

As far as overwatering is concerned, I have a lot of experience. I have killed many plants by overwatering them over the winter, and by trying to get tubers and rhizomes back into growth in the spring. It has taken me a long time to work this one out.

Tubers planted in the garden are rather less susceptible to overwatering as excess water can drain away, whereas compost in a pot tends to retain moisture and can get very wet.

 

Thank you for the information Peter, I'm one for over watering if it lives in the back garden its got to like water,

Reading around, various growers bring them on in the greenhouse/living room window etc with great success, maybe I was lucky , I bought them from the pond shop I remember putting them in thinking what a strange looking seed .

 

Not too hot for me either....agree with Peter.
wet cold conditions will cause dahlias to rot.
However, dahlias grown in full growth in the summer, enjoy plenty of water and sunshine. They are greedy for water, nutrients and sunshine. Currently have several dahlias in flower and those growing in pots are watered generously daily.

 

I am not too sure why the tubers are being started of inside now? fair enough in the Spring but it's June and unless @BrandNewGardener lives at the North Pole there is no risk of frost so much better IMO to have the tubers either planted outside in the ground or in pots.
I have grown Dahlias for god know how many years and over wintered the same tubers for anything up to 20 years. To me they are very very similar to Potatoes in that they will sprout all by themselves without any watering if given a bit of light come Spring when the weather warms up . Often if we have a warm end of March/beginning of April my tubers will have sprouted before I've gone anywhere near where I store them (top of wardrobe in spare room). The tubers usually holds enough moisture and fuel to get going with no help needed. Occasionally if the tubers are very wizened then I will soak them for 24 hours prior to planting. Certainly I do not plant deep which may be the cause of the problems. I plant with the top of the corms just visible and therefore the new growing points which are located near the old stem are above soil level.

 

I think Silu has summed it up.

I recently bought a Voodoo Lily (Sauromatum) - illustrated above, and that can grow and flower from the tuber without any soil, water or roots. The roots start to appear after the flower has died down.

 

I have just remembered - I read a book on Dahlias some time ago and posted a summary of what it said here. Dahlias - 10 things you didn't know

I am no expert, I simply repeated what the book said.

 

Thank you all so much for replying, this has all been really useful. I'm learning lots!

@PeterS thank you for that. Interesting stuff! I think I might have to put that book on my wish list to Santa.