Forsythia Leaf Curl and Drop: Moisture Stress, Not Fungus

Symptom Pattern

Dwarf forsythia: leaf curl → yellow → brown, progressing bottom to top over weeks. Insecticide ineffective. No leaf spots reported.

Expert Lean: Moisture Stress

• Too Dry: Summer heat + insufficient watering (shallow roots).
• Too Wet: Poor drainage + frequent rain = root suffocation.
• Bark Damage: Check base for mower/trimmer injury or rodent chewing.

Immediate Actions

1. Soil Check: Dig 6" down—should be moist, not soggy or powder-dry.
2. Deep Water: Slow soak 1×/week if dry; improve drainage if wet.
3. Base Inspection: Clear mulch; look for constricted bark, holes, chewing.
4. Wait & Watch: Forsythia is tough. New growth often emerges from crown if roots alive.

When to Suspect Disease

If leaves show distinct spots, lesions, or powdery coating → fungal. Then: rake leaves, improve air flow, consider fungicide (chlorothalonil) next spring.

Most "dying" forsythias are just thirsty or drowned. Check the soil first.