Flour Power
So can somebody explain why native prairie plants, adapted to this climate, get far more powdery mildew each summer than my non-natives? I just made a list of the natives in my garden—25 in all, including the spring woodland species—and what gets the worst—absolutely the worst—powdery mildew of all?
Photos: Ron Capek• The 4-foot tall, purple-flowering Verbena hastata, looks this summer as if I had just dumped a 5-pound bag of Pillsbury’s best bleached flour all over it.
• The slightly shorter Verbena stricta (dear to my heart because it thrived in the cow pastures of Kansas where I grew up) is getting ready to follow suit.
• Oenothera biennis, one of Nature’s wonders that I must, must, must have in my garden because its flowers unfold in seconds right before your eyes every summer night around 8:30, will soon be shockingly ugly, and the leaves of the Joe Pye weed will follow suit.
WHY?
Yes, it’s humid, but Chicago doesn’t have a monopoly on moisture. I learned that one hot, soggy August day when I boarded a plane at Midway and disembarked an hour later in an equally hot and soggy Kansas City.
So what’s going on here? Why aren’t my “exotic” plants also encased in mildew? Especially since the early part of the season was super wet? Yet even my phlox are still looking good.
Does anybody know?
— Carolyn Ulrich
Posted by Chicagoland Gardening Blog at 8/17/2009 2:02 PM 
Categories: Summer Garden Plants, Native Gardening
Categories: Summer Garden Plants, Native Gardening
Here in NC, we see this a lot on a certain species. It can affect one and not the other. Some varieties are resistant to this mildew. The mulch below the plant will hold the mildew until the next yr which increases the infection. Remove the affected mulch. An organic remedy is to spray each morning with this solution:
5% acidic apple cider vinegar in a gallon of water.
Spray the leaves each day until you no longer have a problem. Don't saturate the ground with it. The ph of your soil is important too.
I would test this on the leaf and make sure it's not going to cause an adverse reaction. I've not known it to.
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Sort of the same thing happening in my garden. Except the plants getting powdery mildew in the garden are the weeds. So far my annuals like Zinnias and sunflowers which always fall victim to this are clean.
Crossing fingers.
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I too have noticed a lot of powdery mildew on the natives this year. Wish I knew, too . . . And why do black-eyed Susans get so much leaf spot?
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Michelle; Roy Diblik told me this spring that this is common when too many are planted too close together. He says it gets into the soil and you have to either replace the soil or plant them elsewhere. What he does for his know maintenance gardens is mix them in with other perennials so the density does not allow the fungus to get out of hand.
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