To divide dahlia tubers, use a gardening knife to cut the tubers into sections that each have a shoot stub. After cutting, dry the tubers pieces before storing. Divide the dahlia tubers during the spring season, and cut only those that have the shoot stubs.
Divide those dahlia tubers that were dug during the fall season after the first frost. After digging, store the tubers in a cool and dry place at 32 degrees Fahrenheit and above during the winter season. Use moist peat to store the tubers. Divide the tubers only after the last average frost date for the locality is announced during the spring season.
Begin dividing by applying rubbing alcohol over a gardening knife. To do this, soak a rag in the alcohol, and wipe the sharp device with it. When dividing, slice via the stem so that all the cut pieces have a minimum of one eye or shoot stub.
Eyes on the dahlia tubers, which are located on the stem's base, appear as white or pink-colored dots. These are the points from which newer stems come out the subsequent year. If the eyes are not visible on the tubers, keep them in a moist and warm area so that they sprout.
After dividing, apply sulfur dust on the tubers' sliced ends, allow them to dry at 50 degrees Fahrenheit in a dry and dark area, and store. Alternatively, plant the cut pieces at a depth of 6 to 8 inches in fertile soil with adequate sunlight.