Larry I almost exclusively overhead water, it seems to work better for me with all the different plants. Powdery mildew is not my nemesis with zinnias it's that other fungus, leaf spot. My Profusion zinnias had it in '14 but the flowering was well so PROFUSE it didn't matter. I had Giant Purple and Lilliput this year and they were disappointing, lanky, sprawling AND leafspot. The Lilliput reseeded and bloomed again in Sept and Oct and were beautiful, a little spotting before the frost took them.
Did you have any difficulties with either fungus?

Almost every year it seems I get some type of leaf spot, not sure which type but heck, maybe all three listed in this article below. I have never really tried to determine which type, just ugly spots that make the foliage look terrible. I usually water overhead also, not sure that makes a lot of difference.I have worked on trying to space the plants further apart, but I guess I am too lazy to get really accurate with it. This article recommends almost two feet of space, but mine are often much closer. Still the odd ones that pop up here and there that are way further apart still get leaf spot. Also the article states that commercial sprays are not effective against leaf spot, so I tend to just pull them when they look really bad, and let new seedling replace them throughout the year.
Of course this year I had a few Zinnias up till the middle of December.
Every year the zinnias start out with that pretty green foliage and I think well this year there will be no ugly foliage, but then it starts and will finally take over the entire plant.
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