Ed. — Archived from the Sunday, June 23, print edition.
VIRGINIA BEACH — All Virginia Beach gardeners know the challenges of keeping plants healthy during the long, hot summer. Insects attack and dry, hot weather often take their toll for a time. Then, the drought is followed by excessive rain and high humidity, which creates the perfect conditions for diseases to spread.
Zinnias always seemed to me to be one of the few very hardy plants that thrive through the worst of what our summers offer. I was startled, then, to notice some pretty sick looking zinnias this spring.
The grey or brown spots on the leaves of some zinnias, which I saw displayed in nurseries, are usually signs of a fungal disease. North Carolina State Extension identifies powdery mildew and leaf spots as the most common two diseases in zinnias, and they are most likely to attack zinnias grown in shady, moist areas. Excessive rainfall or overhead watering can also encourage an outbreak.
That makes sense. I was shopping for zinnias during a cool, rainy period in the late spring, and the plants’ leaves were very wet. These poor, soaked, sun-starved zinnias were showing symptoms of alternaria blight, a fungus that causes circular or irregular spots on the leaves.
The affected leaves usually turn brown and die, and the unsightly spots can appear on the stems and blossoms, too. Sometimes, cankers appear on the stems, and this can result in root rot. The affected plant often dies, but the disease can remain in the soil and plant material for two years.
Still, I wanted those zinnias very badly. I hadn’t had too much luck getting my own seeds to germinate, and I was impatient to get some zinnias established because it was getting late in the spring.
So I bought the plants, brought them home and treated them with a mixture of baking soda, soap and water. I’ve used this DIY anti-fungal for years, particularly on sweet basil, which seems extremely prone to fungi.
Virginia Beach Master Gardener Michael Horstman, however, recommends potassium carbonate, which can be ordered online, rather than baking soda.
While baking soda works, gardeners risk a salt build-up in the soil with repeated use over a long period of time. Besides, the potassium is also good for the plants, Horstman said.
Whichever you prefer, mix about one teaspoon in a quart of water, add a splash of a mild liquid soap and, if you want, a drop of cooking oil. Remove the affected leaves and spray this on the remaining leaves as a preventative measure.
Repeat this often, particularly after a rain. Be careful to remove any plant debris so that the soil doesn’t become affected, and sanitize any gardening tools that have been used on the affected plants.
And don’t forget to wear gloves and wash them well before you handle other plants.
North Carolina State Extension also suggests planting zinnia cultivars from the Profusion Series, a disease-resistant cross between zinnia angustifolia and zinnia elegans. These zinnias come in a variety of colors, and they’re long-blooming, drought tolerant and don’t require deadheading.
You can also use a commercial anti-fungal such as Neem Oil, but I usually first look for ways to do things with common kitchen items that I already have on hand. It saves money, and I’m also spared the time and frustration of shopping for emergency supplies to combat problems such as disease and insects.
I’m pleased to say my zinnias now appear happy and disease-free, but now I have an even worse problem.
As I wrote this, I saw my first Japanese Beetle of the season on my evening primrose. It’s time to mix up a spray bottle with about four tablespoons of dish detergent in a quart of water. This is the easiest, quickest, cheapest pesticide that I know.
And, like the baking soda mixture, it usually works.
The author is a contributor to The Independent News. Her journalism has also appeared in The Virginian-Pilot.
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