Perennial flowers often become crowded after two or three years. Crowding may inhibit blooming or cause the plants to die off completely. Splitting the flowers apart into multiple plants, also called dividing, allows you to replant them at a healthier spacing. Splitting also gives you access to free plants, which you can then use to extend your garden bed or to replace older plants that are no longer in their peak of health. Split spring and summer flowering plants in the fall and fall flowers in the spring, advises Clemson Cooperative Extension.
Water the flower bed thoroughly the day before dividing so that the soil is easier to dig in. Moisten the soil to at least a 6-inch depth.
Dig around the plant that is to be divided with a trowel. Dig down slightly deeper than the roots and then slide the trowel under the plant and lift it from the ground.
Inspect the root system of the plant. Fibrous-rooted plants have a tangle of small roots. Thick-rooted plants have single or multiple rhizomes or large-diameter roots.
Work your fingers into the root mass of fibrous-rooted flowers, teasing the plants apart. Alternately, set the plant on the ground and insert two spading forks, back-to-back, into the center of the plant mass. Pull the forks apart, separating the plant into two.
Cut apart thick-rooted flowers with a clean, sharp knife. Cut the roots so there is at least two buds or leaves on each root section, cutting the sections down to 2 to 4 inches long.
Discard any rotted or dead plant matter. Separate or cut out rotted areas of the plants before replanting them if only a portion of each division shows signs of disease or death.