Every summer our red monarda plants develop what looks like powdery mildew on...

Asked June 17, 2014, 1:55 PM EDT

Every summer our red monarda plants develop what looks like powdery mildew on their leaves. The plants are otherwise healthy looking and seem to thrive, but for these "mildewy" leaves. Is this anything to be worried about, and is there a remedy? The accompanying photo shows the state of things as of 6/16/2014. Once again, many thanks for your assistance

Montgomery County Maryland

1 Response

Looks like the foliage on the monarda was subject to powdery mildew, a fungal disease. This can be common on bee balms. Symptoms are most severe on over-crowded plants and those growing in partial shade. To reduce the severity select a site that receives at least six hours of direct sun each day and space plants 2 to 2½ feet apart. Move plants growing in partial shade to a sunny location. Divide bee balms every two to three years to prevent overcrowding. Remove and destroy disease-infested plant debris in fall.
The best way for home gardeners to avoid powdery mildew is to select and plant mildew resistant varieties. Varieties that possess good to excellent resistance to powdery mildew include ‘Marshall’s Delight’ (bright pink flowers), ‘Jacob Cline’ (deep red flowers), Grand Marshall™ (fuschia-purple flowers) and ‘Raspberry Wine’ (wine red flowers).
mh