⚠ MinorWhite powdery coating on rosemary stems � uncommon, and usually a sign the plant needs more sun and airflow.
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Fungal
Powdery Mildew on Rosemary
Commonly affects: Salvia rosmarinus (Rosemary)
A white, powdery coating develops on stems and needle-like leaves, usually in humid, still conditions. Affected growth can look dusty grey-white and may weaken over time.
Potential Causes
- 1High humidity combined with poor air circulation, especially in overcrowded plantings
- 2Overhead watering keeping foliage damp
- 3Shady, still conditions with limited airflow � unusual for a plant that prefers dry, open, sunny spots
Solution Steps
- 1Move the plant to a sunnier, more open spot with better airflow if it isn't already in one.
- 2Water at the base only, avoiding wetting the foliage.
- 3Prune out dense, crowded growth to improve air circulation through the plant.
- 4Apply a potassium bicarbonate or sulphur-based spray at the first sign of white patches.
Prevention Tip
Rosemary rarely gets powdery mildew when grown in its preferred full sun with good airflow � if it appears, the growing spot itself is usually the underlying issue to fix.
