Gardening with Galligan: Backbones of the summer garden

CAROL GALLIGAN PHOTO | A healthy stand of rudbeckia in full sun. The pink in the background is ordinary garden phlox.

Last week I said I would spend some time on the powdery mildew that affects phlox, one of the mainstays or backbones of the summer garden.

To begin with, it certainly renders the plants unsightly, causes them to lose leaves, droop and be covered with what looks like spots of baby powder. Interestingly enough, the disease doesn’t seem to damage the plant over the long haul; the following year they come back in full strength. But looking at them as the summer wanes is indeed unpleasant.

Powdery mildew is a fungus and is easy to diagnose since the symptoms are looking straight at you. One of my nieces once telephoned, close to tears, asking what was happening to her favorite potted plant. “It looks like someone sprinkled baby powder on it!” Yes, it does. The infected areas are filled with powdery white spots on both leaves and stems. The lower leaves are usually the most affected. As time goes on, the spots get larger and the mildew spreads.

The fungus thrives in environments of warm temperatures and high humidity — in other words, here. You can spray with an anti-fungal mixture, cutting off the diseased material, bagging it and disposing of it in the household garbage; dont’ toss it into the woods. If it has struck one of your houseplants, however, simply carry the plant to the sink and wash the mildew off the leaves. Then dry them and spray with an anti-fungicide. Aunt to the rescue!

We might pause to think about plant diseases. If someone asks you, what are the black spots on your roses, the answer is that’s Black spot or “Diplocarpon rosae” disease. What are those strange looking streaks of rust? That’s rust fungus. The second thing I think about in relation to plant diseases, is that there are fortunes to be made out there if someone would only get their act together. A systemic cure for Black spot in roses is worth millions. In a conversation with an epidemiologist friend, I once commented on this and he became very interested and excited for about a week; then the Center for Disease Control issued some interesting and complex finding and Black spot could not compete.

And now on to another mainstay of the summer garden, rudbeckia, popularly known as black-eyed Susan, a stalwart, easy to get along with, undemanding, cheerful, pretty friend. A member of the family Asteraceae, they are natives of North America, perennial and herbaceous. They come in all shades of yellow and orange. They are also often referred to as “cone heads” because of the inclination of the bloom to point downward as the plant opens. Rudbeckia species are used as food plants by caterpillars of some butterfly species including Lepidoptera, and some of the fancier moths.

The plant was named by Carolus Linnaeus to honor his teacher at Uppsala University in Sweden, Professor Olof Rudbeck the Younger, 1660-1740, as well as his father, Professor Olof Rudbeck (you guessed it!) the Elder, 1630-1702. We should put them on our list of plantsmen to learn more about when the fall is upon us. Actually, now and again in the past week, in the late evening one can feel just a hint of fall in the air.