Troubleshooting
New England Aster 'Purple Dome' problems — and how to fix them
New England Aster 'Purple Dome' (Symphyotrichum novae-angliae) 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
'Purple Dome' has improved resistance but can still be affected in humid, still conditions; ensure good spacing and water at the base.
Stem splitting
Rapid growth after rain or irrigation can cause stems to split; cut plants back by one-third in late spring (Chelsea chop) to encourage bushier growth.
Aphids
Colonies of greenfly on shoot tips in spring; treat with insecticidal soap or introduce natural predators such as ladybirds.
Clump die-out at centre
After 3-4 years, divide clumps in spring, discarding the woody central portion and replanting vigorous outer sections.
Prevent new england aster 'purple dome' problems before they start
Most new england aster 'purple dome' issues are care-mismatch, not bad luck. Dial in the basics:
New England Aster 'Purple Dome' problems — FAQ
Why is my new england aster 'purple dome' powdery mildew?
'Purple Dome' has improved resistance but can still be affected in humid, still conditions; ensure good spacing and water at the base.
Why is my new england aster 'purple dome' stem splitting?
Rapid growth after rain or irrigation can cause stems to split; cut plants back by one-third in late spring (Chelsea chop) to encourage bushier growth.
Why is my new england aster 'purple dome' aphids?
Colonies of greenfly on shoot tips in spring; treat with insecticidal soap or introduce natural predators such as ladybirds.
Why is my new england aster 'purple dome' clump die-out at centre?
After 3-4 years, divide clumps in spring, discarding the woody central portion and replanting vigorous outer sections.