Troubleshooting
Aster 'Purple Dome' problems — and how to fix them
Aster 'Purple Dome' (Symphyotrichum novae-angliae 'Purple Dome') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Powdery mildew
More resistant than most New England asters but not immune; ensure an open, sunny position with good airflow.
Root rot
Caused by heavy, waterlogged soil particularly in winter; improve drainage before planting.
Aphids
Appear on new shoot tips in spring; use insecticidal soap or encourage natural predators such as ladybirds.
Crown die-back
Older crowns become woody and unproductive; divide every 2-3 years in spring to rejuvenate.
Rust
Orange pustules on leaf undersides in humid conditions; remove affected leaves and avoid overhead watering.
Prevent aster 'purple dome' problems before they start
Most aster 'purple dome' issues are care-mismatch, not bad luck. Dial in the basics:
Aster 'Purple Dome' problems — FAQ
Why is my aster 'purple dome' powdery mildew?
More resistant than most New England asters but not immune; ensure an open, sunny position with good airflow.
Why is my aster 'purple dome' root rot?
Caused by heavy, waterlogged soil particularly in winter; improve drainage before planting.
Why is my aster 'purple dome' aphids?
Appear on new shoot tips in spring; use insecticidal soap or encourage natural predators such as ladybirds.
Why is my aster 'purple dome' crown die-back?
Older crowns become woody and unproductive; divide every 2-3 years in spring to rejuvenate.
Why is my aster 'purple dome' rust?
Orange pustules on leaf undersides in humid conditions; remove affected leaves and avoid overhead watering.