Troubleshooting
Aster 'Alma Potschke' problems — and how to fix them
Aster 'Alma Potschke' (Symphyotrichum novae-angliae 'Andenken an Alma Pötschke') 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
Almost universal on New England asters in warm dry spells; choose open, sunny sites and consider mildew-resistant selections or preventative sulphur sprays.
Leaf spot (Septoria)
Brown spots with darker borders on lower leaves; remove affected foliage and improve airflow.
Aphids
Mainly on young shoot tips in spring; treat with insecticidal soap or a strong water jet.
Flopping stems
Tall cultivar prone to lodging; Chelsea chop (cut back by half in late May/early June) reduces final height and eliminates the need for staking.
Crown congestion
Woody unproductive centres develop after 2-3 years; divide every 2-3 years in spring, discarding the old centre.
Prevent aster 'alma potschke' problems before they start
Most aster 'alma potschke' issues are care-mismatch, not bad luck. Dial in the basics:
Aster 'Alma Potschke' problems — FAQ
Why is my aster 'alma potschke' powdery mildew?
Almost universal on New England asters in warm dry spells; choose open, sunny sites and consider mildew-resistant selections or preventative sulphur sprays.
Why is my aster 'alma potschke' leaf spot (septoria)?
Brown spots with darker borders on lower leaves; remove affected foliage and improve airflow.
Why is my aster 'alma potschke' aphids?
Mainly on young shoot tips in spring; treat with insecticidal soap or a strong water jet.
Why is my aster 'alma potschke' flopping stems?
Tall cultivar prone to lodging; Chelsea chop (cut back by half in late May/early June) reduces final height and eliminates the need for staking.
Why is my aster 'alma potschke' crown congestion?
Woody unproductive centres develop after 2-3 years; divide every 2-3 years in spring, discarding the old centre.