Controlling Powdery Mildew on Zinnias: Prevention and Treatment

The Problem

White film on zinnia leaves is powdery mildew. It weakens but rarely kills the plant. Since zinnia leaves are stripped for bouquets, it's often cosmetic.

Control Measures

• Spray Green Cure (potassium bicarbonate) weekly.
• Homemade alternative: 1 tbsp horticultural oil + 2 tbsp baking soda per gallon water, weekly.
• Key: Start spraying before symptoms appear, when plants are small.
• Water in morning only; deep, infrequent watering. Keep foliage dry.
• Remove and trash (not compost) infected plant debris at season's end.

Follow-Up: Echinacea Risk

Echinacea rarely gets powdery mildew, but not impossible. Protect with same sprays or accept the risk—gardening has no guarantees.