I am sorry to see this. It must be heart breaking to put all the effort and get this kind of a result. I am very new to growing them, so I am sure more experienced growers would chime in. May I suggest the following:

1. If you suspect any issues with the soil condition, try to grow some in containers with external soil source; apply phosporous (bonemeal or other sources) to ensure healthy flower growth.
2. If you suspect the quality of the planting material is the issue, try new sources next year.
3. Ensure adequate sunlight (this was one of my biggest learnings this year!) for the plants.
4. Watch out for bugs (I don't think that is your major issue here).

My 2 cents.

Dfever

Herbicide poisoning from contaminated compost or grass clippings(even some potting soil has done this!)is my guess. Dahlias are especially sensitive the commercial grass herbicides. Herbicide(not Roundup as it is ok) sprayed on weeds prior to planting dahlias is also a cause as it remains in the soil for a year or two. No cure is available except that tubers will probably grow well next year if not exposed to herbicides.

I definitely didn't spray herbicide...
But the tubers were purchased from Walmart, I'm sure you know what I'm talking about.

The potting soil was Bacto brand. These tubers I planted last year and they survived the winter, the soil didn't change at all except I added more on top of it .

The tubers that you bought are not likely to be bad. I still suspect herbicide damage from some source. Dahlias are easy to grow and even those bought at Wal Mart(grown in Holland) should do well. One of our dahlia club members used a local brand of potting soil and had similar results. They refunded her money and acknowledged the contamination. They also sold it to a Master Gardener club and they lost all their vegetable starts.

OK so assuming it is my potting soil, what should I do?

Should I wait for dormancy and dig them up?

Everyone's told me dahlias don't overwinter in the ground, but mine all came back, and we even had "Icemageddon 2014" down here.

Since you paid very little for the tubers at Wal-Mart, I would do as you did last year and if you want them, mulch them again. Buy new tubers from a real dahlia nursery next year. The varieties sold at Wal-Mart are not the best.

>>The varieties sold at Wal-Mart are not the best.

True that. Although I do confess that all of mine are Home Depot varieties and perform beautifully.

They're common, sure, but still very pretty. Just because it's common doesn't mean it can't be a great plant that's a joy in your garden.

I'd be more worried about Wal-Mart's cut-rate policies on goods. Ten to one the nursery isn't the best and it's more than likely they don't trim out virus-infected tubers.

The big chain stores like Lowes, Home Depot, Wal-Mart, Costco and many others buy Dutch grown dahlia clumps(note: not tubers but small clumps of tubers). There are several companies that sell them so it is unfair to lump them all together with negative comments. The Dutch have done an excellent job of selling healthy dahlias with little or no virus. Some people have gotten Dutch stock and said it was the best they ever had. The mis-labeling is my biggest complaint. And this even goes further in that they are now selling packages of several varieties with no indication as to the names of the varieties. It would be nice if some consumer watchdog would buy a bunch of Dutch grown dahlias and tell us what companies are better. Meanwhile, I bought one Dutch tuber clump this year and it was not the one named on the package.

" Ten to one the nursery isn't the best and it's more than likely they don't trim out virus-infected tubers."

Ted had recommended a 'dahlia nursery,' which specializes in dahlias and make it their business (literally) to sell good stock. The nursery down the road that sells whatever is in season most likely buys dutch varieties in a large batch, and starts them in pots to sell to you.

Here is a list of US dahlia nurseries, most of which are reputable... But buyer beware, as in all things.

Here is a link that might be useful: Dahlia Vendor Big List

Desirai, it sounds like you might be having a soil fungal problem, which might be compounded by keeping them in the ground where they are wet all winter.

If this has been happening two years in a row, I would find a fungicide that you can use as a drench, and water each plant thoroughly up to a foot around the stem as soon as you can... Personally, I'd do it again right after frost and in the spring to try to knock out the problem. That might be overkill, though.

Good luck!

>>The big chain stores like Lowes, Home Depot, Wal-Mart, Costco and many others buy Dutch grown dahlia clumps(note: not tubers but small clumps of tubers). There are several companies that sell them so it is unfair to lump them all together with negative comments.

I still don't trust Wal-Mart just on general principles. :)

But I take your point.

>>The mis-labeling is my biggest complaint. And this even goes further in that they are now selling packages of several varieties with no indication as to the names of the varieties.

Agreed. While packaging mistakes do happen, they shouldn't be common. So far, my Home Depot purchases have all contained the exact cultivar listed on the package. They've even contained more viable tubers than the package claimed in the case of higher volume packs--although the one or two tuber packs usually do contain exactly one or two tubers.

So far, I have no complaints. They're not going to be unusual dahlia, but for most of my beds, I'm not looking for anything particularly unusual. A central plant of moderate interest is what's called for to avoid yanking attention away from the rest of the design and diverting too much interest away from other, less flashy, species.

I grew some dahlias from seed this year that are pretty cute. although something made a snack of them.

This isn't my first time with dahlias, but it has been several years. I bought mine from a Dutch grower and shipped directly to me. Planting them and getting them to grow hasn't been an issue. My problem is now the buds are dying on one stalk while the next one is fine. I'm also seeing a flowering one suddenly fall down from what looks like the base of that stalk being either eaten or drying out (it's hard to tell).

Anyone have any clue to what's going on?

By the way, I live just south of Boston, Ma and we've had a recent spell of very cool nights followed by a week of hot weather.

Thanks

These are pictures of what I'm seeing today.

What looks to be dried out/bitten off.