Congrats on your new house!

Looks like the top clump with five tubers was planted this spring with a single mother tuber, while the other two massive clumps were not divided the previous year.

I would have recommended you NOT wash them, and store wrapped in newspaper in a loose plastic shopping bag until spring, when you could divide out small chunks or tubers with sprouts.

Since you obviously already washed them, I'd recommend you dividing the monster clumps 2-3 times to make sure mold doesn't destroy the whole clump. A good way of doing that is to pull apart the stalks, not worrying unduly about losing the odd tuber here and there. The idea is to make sure the inside can thoroughly dry and cure before packing away.

Hope this helps!

Thanks so much !! I was on The fence about washing them but what a mess!!! The previous owner told me she had NEVER split them, and I think they were 5 yrs In The house ...
I have them drying in the garage, and will take your advice and split the huge clumps.
The whole neighborhood will have dahlias next year :-)

I hope the stems pull apart for you. The future plants will come out of the old stalk closest to the individual tubers, and it might be tricky for you to divide them with a tool right now. If you google 'dividing dahlias,' there are tons of youtube videos and step-by step tutorials on how to do it, but if this is your first year growing dahlias, I would encourage you to tackle it in the spring when the sprouts are very clear.

Doing it now might be... frustrating... to say the least. Many old-timers that are given undivided clumps like that end up thanking the person for their gift, then run the clumps to the compost pile as quick as they can after the person is gone. It is simply not worth the time and effort for them.

Here's a first year clump...

Same clump pulled apart. Didn't need to use pruners on this clump, though often the stem or tubers are attached to two pieces and must be sacrificed.

I tried to do this to another clump today, and the dratted stems popped right out of the clump, leaving the same tight ball of intertwined tubers. I grabbed half with each hand, and sharply twisted the parts away from each other, with the same effect as the image here.

Granted, this is with one year clumps. I have not had the dubious pleasure of trying to divide a five year clump!