Powdery Mildew
A fungal disease that dusts leaves with a white, flour-like coating, spreading in warm, still, crowded air.
🔍 How to spot it
White or greyish powdery patches appear on the upper leaf surface and stems, as if the plant has been dusted with flour. It usually starts as small spots that spread and merge, and unlike dust it does not wipe cleanly away. Badly affected leaves yellow, distort and drop.
💥 The damage it does
The fungus coats the leaf and blocks light, weakening the plant and stunting growth over time. It rarely kills a healthy plant outright but disfigures it and saps vigour, and it spreads readily to neighbours in still, humid air.
🧴 How to treat it
Remove and bin the worst-affected leaves, and improve airflow around the plant at once. A spray of diluted potassium bicarbonate, or a milk-and-water solution, checks mild cases; sulphur-based fungicides handle stubborn ones. Avoid wetting the foliage when you water.
🛡️ How to prevent it
Space plants for good air movement, avoid overhead watering, and keep them out of warm, stagnant corners. Feed and water steadily so plants are not stressed, and grow mildew-resistant varieties outdoors where you can.
🌿 Plants that get powdery mildew
Common on many garden plants, herbs and some soft-leaved houseplants. These 120 profiled plants name it in their own troubleshooting notes:
Houseplants 20
Garden 92
Struggling to save a plant? The plant rescue guides walk through recovery step by step, and the problem solver works backwards from a symptom. This is general growing advice, not a diagnosis for a specific plant.