I store various ones in each of those three methods. Some I leave in our free draining ground but build bracken mounds over them, others stay in their pots and the ones I am going to move anyway come out and are stored without soil, wit the pots, in our shed. The one downside to storing out of soil is also an advantage. You can damage the tubers as you dig them up but you can see any tubers that are rotting and remove them, which you can't with dahlias left in soil. Soil insulated them a little better so they can take more cold and it just means if you lift them you have to make sure the tubers are kept above freezing.
The issue nobody has mentioned, is that if you leave them in the ground, the new shoots are very susceptible to mollusc damage. I find this is much less, if I dig them up, plant into pots in the Spring and not plant out until they are substantial plants.
How can you lie there and think of England When you don't even know who's in the team
Mine are lifted, then put into large fish cases and covered in straw I make sure it is all a bit damp and then they are moved into the room our furnace is in.
We do get slugs here but not as badly as many people so my dahlias outgrow them rapidly. They don't show any shoots until early May but then they grow like crazy and will be 2 feet tall by the end of May. I think the molluscs prefer more moisture. Snails used to be more of a problem than slugs but we've not had so many over the last few years. I've no idea why, maybe they don't like the cold dry springs and hot dry summers we've been having.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
I lift the ones in pots and store them in newspaper in the outhouse. Then in the spring when I start them off in other pots I have great fun wondering what variety they are as I forget that I wrote that on the now discarded newspaper. The ones in the ground are left as we have dry sandy soil and mild winters. And as we have no rain, ever, (or so it seems) we are not particularly troubled by slugs.
A solution to the conundrum @Copperdog may be to leave your Dahlias in their pots over winter and in February (if you can) sow some Dahlia seed. I do this every year. At the end of each season I give most of the Dahlias corms away and leave one or two which I want to keep in the ground ( Called Bishops something or other).
'The power of accurate observation .... is commonly called cynicism by those that have not got it.
I have done cleaning the tubers, keeping in pots without watering, and leaving in the open ground. I have also grown cuttings from spring regrowth. All seem to work. Wet winters kill rather than cold.
End of August is a bit early, or are you just thinking ahead. First frost is the time to part with dahlias.
location: Surrey Hills, England, ex-woodland acidic sand. "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
The issue nobody has mentioned, is that if you leave them in the ground, the new shoots are very susceptible to mollusc damage. I find this is much less, if I dig them up, plant into pots in the Spring and not plant out until they are substantial plants.
I suspect most people who think they lost their dahlias to frost, actually lost them to slugs. Same for Salvia Amistad.
I have been either overwintering them in their pots, or cramming them into a plastic box with plenty of compost left around them. (And a bit tipped over them for good measure). They seem to wake up and start to shoot some time in March IIRC.
"What is hateful to you, do not do to your neighbour".
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The one downside to storing out of soil is also an advantage. You can damage the tubers as you dig them up but you can see any tubers that are rotting and remove them, which you can't with dahlias left in soil. Soil insulated them a little better so they can take more cold and it just means if you lift them you have to make sure the tubers are kept above freezing.
I find this is much less, if I dig them up, plant into pots in the Spring and not plant out until they are substantial plants.
When you don't even know who's in the team
S.Yorkshire/Derbyshire border
The ones in the ground are left as we have dry sandy soil and mild winters. And as we have no rain, ever, (or so it seems) we are not particularly troubled by slugs.
'The power of accurate observation .... is commonly called cynicism by those that have not got it.
George Bernard Shaw'
End of August is a bit early, or are you just thinking ahead. First frost is the time to part with dahlias.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
I have been either overwintering them in their pots, or cramming them into a plastic box with plenty of compost left around them. (And a bit tipped over them for good measure). They seem to wake up and start to shoot some time in March IIRC.