What’s wrong with my dogwoods? And what about my tomatoes?

GARDEN Q&A

My dogwood trees look terrible — discolored and droopy. One looks okay. A few brown spots, but it doesn’t seem like that accounts for how miserable it looks.

The fungal disease of powdery mildew begins subtly with a white haze on sprouting leaves, but progresses to white, purplish-red to brown distorted foliage and some leaf drop. We’ve been swamped with questions about it this spring, suggesting weather conditions were ideal. (Related powdery mildew diseases also are infecting plants such as crepe myrtle and monarda at high levels.)

Powdery mildew is not new and rarely kills dogwoods; it weakens them and looks unsightly, but now we are dealing with a new imported, more infectious version. Thanks to DNA diversity in our native dogwoods, their susceptibility to powdery mildew varies. You’re seeing a range of resistance even in your home landscape.

Pruning for better air circulation can help. It’s too late this year for a fungicide spray. Water your dogwoods during droughts (especially in the fall!) In the future, plant only powdery mildew resistant varieties. There are good ones available. This is a native tree adapted to Maryland and well worth planting. Search ‘powdery mildew’ on the Home and Garden Information Center website for tips and a list of powdery mildew resistant varieties.

In the past, my tomatoes grew well in pots on a sunny deck. This year, the lower and middle leaves are turning yellow and some have brown spots. I water carefully and fertilize all plants. I would greatly appreciate a diagnosis and treatment. Could this be fungal? Septoria?

Some symptoms could be caused by extreme spring weather and transplant shock; also, older leaves naturally decline.

But by this time in the growing season, the brown spots are probably early blight fungus or septoria, which require similar approaches. They are encouraged by warm, wet, humid weather.

Cut off shoots with yellowing leaves and disease symptoms. This improves air circulation around leaves and slows the spread of the disease.

In your pots next year, use fresh soil free of overwintering fungal spores. In-the-ground gardens need different approaches. On the Home and Garden Information Center website, search ‘tomatoes’ and click on Problems. And be sure to read our recent blogpost about tomatoes, which features excellent photos — including mysterious symptoms you wonder about.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.