Planting dahlia tubers

Hippophae

Hi

I salvaged these dahlia tubers that were in the process of being thrown away. They are clearly still alive as they have growing shoots coming out of them.

Now I realise that it is not an ideal time to plant them now and that I can pretty much forget any expectation of getting any flowers from them this year.

A) Should I plant them now and what is the chance of them surviving until next spring if I leave them in the ground over winter?

Thanks for any help!

JennyJ

I would plant them and see what happens. Whether they survive winter in the ground depends on your soil and climate. If you have well-drained soil and a relatively mild climate, that increases their chances. Mine generally survive and come back bigger every year.

Hippophae

That’s good to hear JennyJ. The site where I would plant them is below a sunny fence so very sheltered and the soil has lots of stones in it so drainage is good too. Sounds like they would have every chance of success. I think I will plant them anyway and see what happens. Can’t really complain if they don’t make it as they were free after all. Appreciate your feedback.

2 point 4

@Hippophae That’s a lovely collection/bargain you have there.

Having an interest in dahlias, I was given approximately 30 tubers in the middle of September 2018 to rescue.  These were breeders’ samples, crosses, etc. which needed to be grown on.  I put each of them in 2 litre plant pots and sat back except for a weak potash feed weekly.  All came up and I allowed them to grow as normal but not flower.  Once the frost had taken the foliage, I stored the pots complete with tubers off the ground in my log store over winter, I.e  somewhere dry. This last spring, I knocked them out of their pots, set them going as normal and have had great fun seeing them flower since I had no idea what to expect.

So the moral of this story is, don’t give up on them!  You have at least a month head start on mine last year!

The only point I would be a bit nervous about is leaving them in the ground over winter. Bishop dahlias are notorious for being fickle and having a reputation for not being hardy enough to survive such treatment.

Hippophae

@2 point 4 thanks so much for sharing your experience. You know planting them up in containers also crossed my mind. I think I will take your advice and do this rather as I really want to give them the best chance possible. I have access to a shed so could move them in there over the winter. I take it once they have died down you leave them completely dry until ready to plant them out in the spring? Also would it be too early to plant them out in April or is May usually better? Last question, what type of soil should I use when planting them in the pots? Will standard multipurpose work or should I use loam based JI? A handful of perlite to enhance drainage?

Dirty Harry

I started quite a few tubers in pots this year with MPC and a few turned to mush, I thought I was being careful with watering.

My advice is include plenty of perlite in the mix, I will be next year when I start them off again.

Hippophae

Thanks Dirty Harry! I watched a video on YouTube presented by Sarah Raven and she recommends using a loam based potting soil for dahlia plants, but I think that’s more for if you intend to grow them in a container more permanently as the loam based soil will hold nutrients better?

I think I will go the mpc with plenty of perlite route though as makes more sense to me in this case.

Dirty Harry

I only have mine in pots so use MPC as it's a lot cheaper and lighter.

2 point 4

@Hippophae Like other posters have suggested, I also used MPC with a goodly amount of added grit.  Since I was going to overwinter them like the breeders do with their pot tubers, I.e. still in their pots, I wanted a medium which would dry out fairly readily and would not leave the tuber sitting in wet soil for an excessive period.

As you may not have as many as 30 to deal with, you could adopt my usual practise of overwintering dahlias.  Ordinarily, I store my tubers upside down in trays with some very dry MPC covering them and these are overwintered like this in my summer house (no greenhouse!).  Your shed will be ideal.  I will turn them the right way up in about March and only then, very lightly dampen the MPC to get them going.  I never plant dahlia tubers directly in the ground without starting them off first mostly because I always take cuttings.  They usually end up in their final positions at the end of April or during May dependent on whether in pots/in the ground and weather conditions.