Dahlias provide annual charm and interest in fall gardens when their bright shows of firework-like blooms light up the otherwise dulling landscape. Dividing their tuberous roots allows you to enjoy even more dahlia blooms next season, and promotes the health of the mother tuber as well.
Dig the tubers carefully with a spade in late fall, after the blooms have all died back. Take care to dig a wide circle around the plant, as new tubers spread away from the mother root.
Cut the foliage back to a few inches of growth at the crown of the tubers and rinse the tuber with water. Once dry, store in containers on a bed of peat moss with a blanket of the same material covering all but the stem.
Divide tubers in the spring before planting. Tubers are joined with several, bulbous roots to one crown. Cut between the bulbs leaving an eye or bud section of the crown intact to each bulb.
Use a clean, sharp knife and sanitize by dipping the blade into a bleach solution and rinsing between cuts to avoid spreading disease.
Store any tubers without identifiable eyes in the peat moss for up to an additional 2 weeks. Eye buds should be obvious at that point, allowing you to re-plant with the assurance that the tuber can bloom.