Troubleshooting
Dahlia 'Penhill Dark Monarch' problems — and how to fix them
Dahlia 'Penhill Dark Monarch' (Dahlia 'Penhill Dark Monarch') 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.
Wind damage
Tall plants and large heads are vulnerable; stake firmly with a stout cane and secure with multiple ties.
Powdery mildew
Frequent on large-leafed varieties; improve airflow and treat preventatively from midsummer in humid conditions.
Aphids
Infest soft new growth and flower buds; treat with insecticidal soap and monitor weekly during summer.
Earwigs
Nibble petals on large blooms overnight; trap with straw-filled pots or corrugated cardboard rolls.
Tuber rot in storage
Dry lifted tubers for at least a week before storing in slightly moist compost or vermiculite at 5-10°C.
Prevent dahlia 'penhill dark monarch' problems before they start
Most dahlia 'penhill dark monarch' issues are care-mismatch, not bad luck. Dial in the basics:
Dahlia 'Penhill Dark Monarch' problems — FAQ
Why is my dahlia 'penhill dark monarch' wind damage?
Tall plants and large heads are vulnerable; stake firmly with a stout cane and secure with multiple ties.
Why is my dahlia 'penhill dark monarch' powdery mildew?
Frequent on large-leafed varieties; improve airflow and treat preventatively from midsummer in humid conditions.
Why is my dahlia 'penhill dark monarch' aphids?
Infest soft new growth and flower buds; treat with insecticidal soap and monitor weekly during summer.
Why is my dahlia 'penhill dark monarch' earwigs?
Nibble petals on large blooms overnight; trap with straw-filled pots or corrugated cardboard rolls.
Why is my dahlia 'penhill dark monarch' tuber rot in storage?
Dry lifted tubers for at least a week before storing in slightly moist compost or vermiculite at 5-10°C.