Be it a tiny, pom-pom bloom or a flower large enough to rival a dinner plate, a simple, single flower or a ruffly, peony-type blossom, the dahlia is an attractive addition to the garden, and not as difficult to care for as you might think. Dividing dahlias is the easiest way to propagate new plants. Dividing dahlias every one to three years will also keep the plant healthy and vibrant, and will prevent the plant from outgrowing its boundaries.
Dig the clump of dahlias carefully, using a garden fork or a shovel. Dig 10 to 12 inches from middle of the clump to avoid damaging the tubers, then lift the clump from the soil. Rinse the dahlia tubers thoroughly with a garden hose and spray attachment.
Divide the dahlia tubers into smaller sections with a sharp knife or a linoleum knife. Each section of tubers must have an eye, as sections without at least one eye won't grow. The eye will be a small protuberance near the top of the dahlia tuber.
Place the tubers in a dry, shady area for two to three days, or until the surface of the tubers feels dry. Put the dry tubers in a paper sack with powdered fungicide, and shake the sack to cover the tubers. Always use the fungicide according to the manufacturer's recommendations.
Place the tubers in a plastic bag or a cardboard box filled with vermiculite, sand or peat moss, completely covering the tubers.
Store the tubers in a dark, cool, non-freezing location until the dahlias can be planted in spring. Temperatures should be about 40 degrees Fahrenheit. Check the tubers occasionally and discard any that have become soft or dried up.