Hi
If possible I would discuss this problem with your supplier. Who knows Dahlias better than them? I'm sure
that the weather as you describe it could have had some
effect. I am new to Dahlias (have had some problems but
not to your extent) Years ago when I dabbled at Exhibition
mums the old timers would sterilize their beds to kill off
any overwintered disease organisms. Don't recall the
chemical used. Wish I could be more help.

You should be in touch with the OR vendor for sure. They don't want to be selling diseased stock any more than you want to buy it. Established, reputable vendors will replace or refund your losses without any hassle, as long as you didn't kill them with overwatering or harsh weather, harsh chemicals etc.

If it's any comfort, I've had more trouble with tubers this year too, no matter where they originated. One plant will grow as predicted at 4 ft, another of the same one will bloom at only a foot tall or stay stunted and wimpy. Diseased plants, eyeless tubers, mislabelled tubers- I've had them all and it is very frustrating.

I would start with the vendor, if they balk, don't buy from them again; and then I'd look to a local dahlia society for some sound advice on how to proceed with your soil, or treat the soil/dahlias if they can ID some disease, if that is a possible problem. MN has some great growers. I'm sure someone would be happy to help and if you describe what happened in detail they may be able to
give you definitive advice.

Good luck. Sorry for your crummy year, but there's always next year's garden, or pots of dahlias on the deck/patio.

Here is a link that might be useful: MN Dahlia Society contact info

Funny you should report a rough year for dahlias also Poochella - I thought it was just me. My dahlias are usually a jungle by this time of the year, and now I've got gorgeous blooms on White Perfection, but everything else looks quite stunted. It could be almost an all white fall - bummer. Well I have 2 opening blossoms on Omega but where are Otto and Edison?

just a thought, white flies? this year has been particularly bad in my area, I have sprayed 4 times.
I do know that the symptoms described can be attributed to these tiny insects and the growth hormone regulators they inject into their host. I have, first hand, seen the dwarfing and yellows to death that white flies can cause.
FWIW

Thanks everyone- next year is always the one of hope- this fall I am going to add aged manure and peat to the soil and stock up on some pesticide -good advice on the white flies I seem to recall that they thrive in dry conditions(even though I hate spraying). Will also mulch to improve water retention- we had floods up here about two weeks ago (here in MN that is) and things bounced back. I think it was just such a hot nasty summer. chalk it up to that I guess!