Hi! ruanich1975, and twinkiedooter
Something in a similar vein...
I don't have the experience with Dahlia's like you do td, but I do with Bulbs like tulips, daffodils, even rhizome's like Irises.
I've wintered them by placing them in shallow 2 to 3" terracotta dishes 'bout quarter to half full of soil,
- Place the bulbs or rhizomes in a pattern.
- Place that whitish with caramel streak river rock ('bout half to one inch size) around them or any rock you like.
- The rocks hold the plant in place and their decorative.
- Follow usual watering habits.
Sometimes it turns out so nice, I'll leave 'em like that for a while.
Eventually though they should be re-placed into Mother Earth, as it will rejuvenate them.
K