Okay, I’ve lifted the dahlias and now I’m going to rinse them although that seems to divide people as to whether it’s a good idea and I haven’t actually done it yet. My real question is do I break them into individual tubers before I store them over the winter or do I leave them attached to each other in a large clump?
I used to rinse ours off too and just made sure to dry them off fairly quickly, though I’ve also left them covered in mud and they were fine too. It’s probably easier to keep them a bit muddier as I imagine it helps a little to stop them drying out, which is how I lost a lot of ours, getting too dry in the middle of winter.
It’s best to separate them in spring when you go to replant them to reduce rot getting into the cut over winter. Although many of ours broke or split apart when I dug them up and were fine too.
I have to say that in almost 45 years of gardening/growing dahlias, I’ve never lifted them. I’ve always left them in the ground and had no problems, other than a jealous neighbour at on point trying everything to get some of my tubers (he eventually got them when I moved out of that house). I’ve always made sure they were planted in light, sandy/gritty soil and they’ve coped with the worst of the weather. I think if I did lift them I’d just brush them off, introducing water to them seems counterintuitive and risks introducing bacteria that wasn’t already there in the healthy tubers.
In previous years I’ve left them and they’ve been perfectly happy. I’m only lifting them because they’re in the wrong place, right at the front of a border. Also I want to create new plants when they start sprouting. I’m not going to use water now. As you say, it seems counter intuitive