Zinnias falling over with powdery mildew

10 years ago

This was my first year growing zinnias. I grew some from seed and also purchased tiny plants early spring. My potted zinnias have been healthy and successful but those planted in the ground have had their ups and downs. First they were attacked by slugs, but the plants that survived the attack grew huge and full, with large showy flowers. However, those same plants are now falling over and recently started showing signs of powdery mildew. Should I have trimmed them back mid-season to keep them from getting so tall? They aren't leggy like a group of them that I didn't have in quite enough sun, the stems are thick and the leaves are large and full. Is there anything I can do for them now or is it too late?

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Comments (5)

zen_man
10 years ago
Hi pinksand,

Try spraying your zinnias frequently with GreenCure. GreenCure is safe and effective against a lot of foliage diseases, including Powdery Mildew.

Apparently your zinnias were falling over before the Powdery Mildew made a showing, so you might try staking at least some of them.

"Should I have trimmed them back mid-season to keep them from getting so tall? They aren't leggy... "

Actually, I like my zinnias tall, because I don't have to stoop over to pollinate or cross-pollinate them. (I am an amateur zinnia breeder).

If you could post some kind of picture of your zinnias, it would give us a better idea of what your zinnia problems are.

ZM
(not associated with any product or vendor mentioned or linked)
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ken_adrian Adrian MI cold Z5
10 years ago
hey zenn-ny ... you are way beyond amateur ...

anyway ... back in the day.. when i was a newbie.. at gardening.. i fert'd everything...

and lots of things fell over ...

how much fert did you use... is there any indication your soil is so deficient of nutrients.. that you needed such??? .. and what formula of fert ...

sometimes we complicate our lives.. by over thinking things ...

ken
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You're welcome. I'm not a flower seller, just a flower lover. I was answering the part about the plant growing deformed flowers. I've not done any research or investigation to see if my cut zinnias last longer if the plant does not have PM. Sorry if that was not clear from what I said. Since moving to AL, I haven't seen much PM, and so far none on zinnias. But if memory serves from when I used to live in OH, flowers cut from plants with PM weren't noticeably shorter-lived. That's as scientific as I can get on that. Good luck!
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NE, "3. Some plants don't like wet leaves and preferred to be watered under their leaves. The wet leaves can mildew." A common misconception about Powdery Mildew is that PM is promoted by wet leaves. That misconception is so widespread that it is now almost an urban myth. Many supposedly authoritative books say that wet foliage promotes Powdery Mildew. Wet foliage does promote many foliage diseases, but not Powdery Mildew. Apparently most garden writers refer to the works of other garden writers and this has become a glaring example of the hazards of "Group Think". The truth is that Powdery Mildew spores cannot germinate in water and that water prevents it. Powdery Mildew grows on dry leaves. Refer to the National Gardening Association's Q&A on Powdery Mildew on Zinnias in which they say, "Powdery mildew is unique among common plant diseases in that it doesn't require a wet leaf surface to spread. It can thus thrive during hot, dry weather, which is why you see it appearing in August. The general advice to inhibit the spread of fungal diseases is to avoid wetting leaf surfaces. In the case of powdery mildew, you can actually inhibit infection with frequent sprays of water." Considering all the books and other publications that are wrong on this subject, and how widespread this urban myth actually is, its going to take a lot of effort to correct this deeply rooted misconception about Powdery Mildew. I am giving it a shot here, but it's a shot in the dark. ZM
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Technically the spores can overwinter in the soil so using a mulch over the soil to prevent soil splash onto the plants is a common recommendation. The thing is the spores are also air born and if they land on a susceptible plant and conditions are right the plant gets infected no matter what. It is believed the PM actually travels via the air from southern states where it starts earlier and makes its way north. The only thing I can suggest is to get in the habit of using preventative sprays such as 1 tablespoon of baking soda and 1 ounce of canola or neem oil per gallon of water. The baking soda kills fungal spores and the oil reduces attachment sites on the plant surface for the spores to take hold. Be on the lookout during rainy periods and avoid overhead watering. Being in Washington state I suppose you have your work cut out for you when trying to avoid fungal pests.
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Donna
10 years ago
Just by way of discussion, I plant the tall zinnias every year. Some years, I pinch them back to make them bushy, other years I don't. The truth is, I see very little difference in them by this time of year. The one thing that seems to help them not fall over is to plant them in groups of 3 or 4 plants, spacing them about a foot apart. They seem to support one another further into the fall. And, you get more blooms close to each other at the same time.
My growing season is so long, though, that sometime in the next month or so, I will pull the plants altogether. They are starting to get fungus spots on the leaves and will eventually look too ratty to bear. Deadheading delays the end, but it will inevitably come before frost.
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pinksand
Original Author
10 years ago
I'm sorry it took me so long to get back! I took some photos of the zinnias but my personal computer died and I haven't been able to upload them :( I actually didn't fertilize them at all, just a layer of spring compost. Maybe that's where I went wrong? I haven't had my soil tested but they are in a new bed I formed this spring by lasagna gardening. The soil seems to be rich, easy to dig into, and full of earth worms. My other annuals planted at the same time are very healthy and lush.

I staked the zinnias that were laying on the ground. There are 5 of them spaced about 1' apart in a grouping, but some fell in the wrong direction. They're all still putting out beautiful large blooms, but the powdery mildew has turned the leaves into a nasty mess! It sound like I need to get some GreenCure! Thank you for the recommendation. I'll need to be more proactive next year, I'm still learning... I guess going through these experiences is a necessary evil in figuring out what works?!
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Deb
10 years ago
I'm wondering if some varieties of zinnia are more mildew-resistant than others. I planted Botanical Interests' Fireball Blend this year and have had no problems with mildew so far. I realize, of course, that we get much less rain than you do in Maryland. But we've just had almost a week of rain here, and I'm still not seeing mildew.

It's probably too late to do much about your mildew problem this year. But next year, you could try a solution of baking soda and water to control mildew as soon as it appears. The solution worked quite well on my zucchini's mildew.

Here is a link that might be useful: mildew control
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Zinnias falling over with powdery mildew

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zen_man

ken_adrian Adrian MI cold Z5

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Zinnias falling over with powdery mildew

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zen_man

ken_adrian Adrian MI cold Z5

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Donna

pinksandOriginal Author

Deb

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pinksand
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