If you grow perennials that include either the purple coneflower (Echinacea purpurea or Rudbeckia purpurea) or the yellow coneflower (Ratibida pinnata), then you'd probably like to keep the plants blooming as long as possible and also keep them looking neat and tidy. These two plants respond well to pruning early in the growing season to promote bushiness and extend flowering, and they can be trimmed later in the growing season and when fall arrives. Both coneflowers are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9.
Trimming for Bushy Plants
A coneflower plant is usually 2 to 5 feet tall and tends to have a narrow growth habit of 1 1/2 to 2 feet wide. It starts putting out new stems in spring, when weather warms, and doesn't bloom for many weeks, usually opening flowers from midsummer through early fall.
Promote a more bushy, compact growth habit in coneflower plants by trimming back each stem by one-half in late spring; doing so prompts branching of the stems and growth of new stems from each plant's base. Trimming this way early also allows the plants enough time to set flower buds, although their blooms may begin to appear a bit later than normal, usually in September.
You also can extend your coneflower bed's blooming period by cutting back some but not all of your plants in spring, leaving the others not pruned. The latter should bloom at the normal time, starting in midsummer, while the pruned group's flowering will be delayed until early fall.
When trimming, use sharp shears, and clean its blades by wiping them with rubbing alcohol before you begin trimming and after each cut. This sterilization helps prevent the spread of plant diseases.
Deadheading for Tidiness
When flowers fade on a coneflower plant, removing the spent blooms -- called deadheading -- helps improve the plant's appearance. Use your fingertips to pinch off flower stems just ahead of the point where a leaf originates on the stem behind the flower, or cut at that point with sterilized shears. The plant may produce new buds after it has been deadheaded, although the second bloom period is usually reduced.
If you want your coneflower planting to expand, allow some self-seeding by leaving a few flowers on the plants to form seeds, which eventually will drop to the ground and produce new plants the next growing season.
Cleaning Up in Fall
Like all herbaceous perennials, coneflowers eventually die back to the ground when winter arrives, leaving dry stems and foliage. You can leave the plants in place during winter, but cutting back their dry upper parts with sterilized tools helps improve the appearance of the flowerbed while getting rid of any remaining insects and their eggs. Remove and dispose of all cuttings when you do fall cleanup. If winter temperatures drop below freezing where you live, then wait until the first frost to cut back the plants to prevent new growth that is easily damaged by cold.