Reviving 20-Year-Old Coneflowers in St. Louis

Established coneflowers (Echinacea) declining after two decades in St. Louis likely suffer from aster yellows (phytoplasma spread by leafhoppers) or excessive moisture from a wet summer.

Diagnosis Clues

• Aster yellows: Stunted, yellowed, deformed flowers; green petals; witches'-broom growth.
• Wet-season stress: Dull color, sparse petals, "cones only" – plants recover when soil dries.

Action Plan

1. Remove and destroy severely affected plants (aster yellows is incurable).
2. Thin clumps: divide every 3–4 years to rejuvenate.
3. Improve drainage: amend with grit/compost; avoid mulch against crowns.
4. Control leafhoppers: yellow sticky traps; neem oil if needed.
5. Black-eyed Susans (Rudbeckia) are not the cause—they coexist naturally.

With division and better drainage, coneflowers often bounce back vigorously.