I've purchased Dahlia tubers for years to plant in my flower pots. Last year I left the tubers (thickened underground stems that send out roots) in the ground. They rotted. This year I'm digging them up and to save over the winter.
Digging up my dahlia tubers:
I waited until November and our first frost to dig up my dahlias.
I trimmed the plants back to three inches of stalk. They were really hard to dig out of my pots, so I loosened the dirt around the edges and worked my trowel underneath to lift the tubers out as carefully as possible.
I let the tubers dry on the surface for a day, and then transferred them to the picnic table to dry for another two days. By then, the soil was dry and easy to brush off. I was amazed how many new tubers were in each cluster.
I used scissors to clip off the feeder roots and secondary tubers coming off the main tubers. Check out Bren W's YouTube video.
I chose not to divide my tubers. Each pot gave me two tuber clusters.
Storing my dahlia tubers over winter:
I placed my cleaned tubers in paper bags for storage. I didn't have peat moss, but had a bag of potting mix.
The clean soil keeps the tubers moist so they won't dry out. The video below recommends periodic checking. If the soil gets too dry, give it a light mist with water. Don't get it overly wet or the tubers may rot.
They recommend a dark cool spot like a crawl space or root cellar that will not freeze. That leaves my cabin out. I chose my spare bathroom in the tub next to my geraniums.
The guides say to keep them at no higher than 50 degrees or the tubers may rot or sprout too early. We keep our condo heaters on low (10 degrees centigrade/50 degrees Fahrenheit) to prevent the pipes from freezing. Sounded perfect.
Here's a YouTube video by Longfield Gardens I used to learn what to do.
I'll let you know how it turns out. - Margy