Ok, Sharon here in Upstate SC. I am relatively new to dahlia growing - at least the digging up and storing part. previously they have overwintered in the ground just fine for me.

This year however, I dug up ~ 15 plants as I want to rework the bed, since I now have a tiller.

I let them air dry on a covered porch, then carefully put each type in an open plastic bag with label and took them to the basement.

When I checked on them after a couple of weeks, several had a fuzzy white mold. I moved those to open shelving on my outside porch and sprayed each with a bleach solution. Now even more of those left in the basement have the fuzz.

We are in the start of our rainy season here. It is probably only going to get worse in terms of dampness.

Is all lost? Do I toss them all, or are there desperate measures to be taken?

If they can be treated, I have an unheated room they would probably do better in than my basement. They did however, do just fince there last winter.

Did the ones you sprayed with bleach solution have a recurrence of the mold? Seems like the best bet would be to dunk the rest in a bleach solution, let them dry thoroughly and then store them in sawdust or vermiculite or sand or something along those lines. And if you have paper bags, I'd use them instead of plastic. But I'm hardly an expert. That just seems like a reasonable thing to do. Hopefully, someone more knowledgeable than me will wander by.

..Sharon, good to see you. We have great people with knowledge here and they will be along also.

I am hardly an expert either but I even went out after a very wet week of rain and saw white fuzzy mold all over my hostas, the whole entire bed was covered, but after they aired out all was fine. No damage at all!

@pirl will be along shortly and maybe she will have better advice, but I would agree with woofie, dry them out and put them in a better place.

I'd spray them with bleach and put them somewhere warm to allow the bleach to dry for a few hours. You could do a test with just one and put it in a plastic bag, add peat moss/sawdust/perlite or vermiculite, and see how it looks 24 hours later. If it looks good, without any mold growth, repeat the process with the others. Please give each one a separate bag so any problem you face won't transfer to the other dahlias.

My reason for not using paper bags is that you still want to give them a spritz of water and I'd hate to see the paper bags deteriorate.

Use new, dry, plastic grocery bags, not the old ones where they had been, which could contain mold spores - dispose of them.

A spritz of water once a month is the standard recommendation. If they shrivel it's difficult to revive them. Sometimes it can be done but why take the chance when you've gone through the work of digging, rinsing, draining, packing and storing?

You are so right about that. Do you mean like one squirt from a spray bottle??

Hmm, I've never "watered" my dahlias stored over the winter. How interesting.

One spritz is all it takes!

The year I didn't do it I lost every dahlia. More than a spritz can lead to rot - been there, done that.

what solution of bleach should I make up to kill the white fuzzy mold?

A 10% solution should do it - one cup of bleach to nine cups of water. You can increase or decrease the volume as needed.

Please let us know how it works for you. Making sure they are dry before you store them (after the bleaching process) is important. You might want to lay down an old towel to absorb any excess of the solution.

The tubers are fine, probably, so don't worry.

Storage mold comes from humidity and poor air circulation. You need to dry the tubers adequately, maybe put them on a tray in the living room for a few days. When they have dried adequately store them in dry peat in trays or even in plastic bags. It is the dry medium that is important.

You could also use the saran wrap method which takes some work. The bleach solutions suggested above would help, but you need to dry the tubers. Even if they get a bit dessicated you can grow them back even from pretty shrivelled. I have a very long growing season so I can afford the time, but it is time lost. However this sets them well back, and you are better to keep them plump by the occasional spray and them back in the peat ( perlite or vermiculite).

If you want you can pot the tubers up in pots with a mix of new compost. Don't water the mix in the pots with the tubers. The mix will be damp enough, and it does not matter if it is a bit dry. Store them in the pots outside under cover where it will not rain on them, a car port or similar, or inside in an unheated place.

Mainly don't worry, dahlias are as tough as potatoes.

Thanks to all for both the advice, and for the reassurance. Thank goddess they are prettier than potatos, for sure!

ok. the tubers have all been checked, the bad/soft ones discarded, and the rest spritzed with a bleach solution. Left them to dry on towels on my kitchen counter and have turned them. so far, so good.

since this is a major lesson learned for me, I might as well expand my knowledge some more.

what exactly is the purpose of packing them in peat? is it to keep them from drying out too much? I have a lot of shredded white paper. would that work as well?

Dampen the paper and pack them up but leave the bag untied. People use sand, sawdust, peat, shredded straw and other mediums.

The purpose is to magically discern the humidity they need so they don't dry out.

Keep them above freezing but less than 50 degrees. You have my best wishes and you've done a great job.

I'm trying shredded paper for the first time this year, so wish us both luck!

I do wish you luck and wish the same for myself! Shredded paper has always been popular and it's easily disposed of when the dahlias are ready to be planted outside.

Hi I just joined, so if I spary the bleach mixture on my dialhias and let them dry again they should be good or OK to plant next spring? Please help. My mother in law grew these flowers til the day she passed away. My father in law gave me some of hers to grow. I planted them last spring and they grew. I dug them up last fall,when I went to plant them this spring they were covered in white fuzzy's. So I still have them in a cool dry place. Please help. Thanks

Hi GrandmaTheresa,
I'm not sure where you are located, but it sounds like the Northern Hemisphere. Are there any sprouts on the dahlia tubers? If so, just plant them, and they will likely grow!

Hi,
Although these notes are several years old, I have also had the problem of white fuzzy mold on my stored dahlias this fall. I first stored them cleaned and in vermiculite, but found they were drying out as the location was too warm. I moved them to the unheated garage covered in moist peat and just checked on them and noticed the fuzzy stuff. I'm assuming from the posts written previously that the peat moss was too damp. I will now try the sprayed bleach solution for each one and dry completely for a couple days, then re-store them in fresh new dry peat moss in new cardboard boxes. I live on the Pacific Coast so winters are very mild. Zone 8b. Does anyone have any more info on this subject to add that might help me before I start the process? I have over 200 tubers so it is very time consuming!