Dahlias come in a wide variety of bloom, search for pictures (images) on the net and enjoy
I had a reader write to ask this question since they are not going to be able to make the garden club meeting tonight.
The answer is yes. You can overwinter in the soil or out, BUT that depends on the type of dahlia you have and to some extent your micro-climate and flower beds characteristics.
Great, so what has that told you? It is a definite maybe. If your dahlias have been living successfully outside for years, your good.
If you just moved to your home or bought tubers without knowing their hardiness, an ounce of prevention may be necessary. I am not aware of anyone hurting their dahlias by removing them from the soil, just do it properly.
So,.... what is properly. For those who do this every year, feel free to add your own details but generally speaking:
wait until a good frost has killed the top of the plant
cut the tops back to about 5" from the tuber
gently remove the clumps from the ground so the "necks" are not broken
Wash the soil off, discard those damaged or showing disease
You might also discard any thin or immature tubers as they will probably not survive the drying and storage. However, I like to give everyone a chance so....
Let them dry about a week in light shade, not bright sunlight. Better if you keep them off the ground or not touching each other.
You can divide now or wait until spring but be sure a stem is attached to each division. This is where new shoots will come out.
After drying, layer the tubers so they are not touching in vermiculite, sphagnum moss, sawdust or even recycled "peanuts". Just don't close them up in a plastic bag. They need air to avoid rotting.
They then need to be stored in a cool, dark space no warmer than 45 degrees (F) If you do not have a protected cellar or crawl space, maybe an old refrigerator?
Watch out for rodents. I am not sure if dahlia roots are delectable to overwintering mice, etc., so taking an extra ounce of prevention may be good. Maybe hanging them in an onion bag? Check on them periodically.