Powdery mildew is one of the most commonly found fungal problems affecting plants. This fungus typically appears as a white or grayish powder on the leaves and stems of affected plants. It affects a wide variety of deciduous plants. Beebalm and phlox have always been common to infection, but in recent years we’re seeing more and more cases of powdery mildew on peonies.
Powdery mildew. It happens.
Powdery mildew on peonies is generally seen in late June through September when temperatures are hot and the humidity is high. In summers with a lot of rainfall, powdery mildew can run rampant. The mildew thrives in shaded areas and areas with poor air circulation.
Even still, it can still be found in very open, sunny areas. Sometimes there’s just no way around it. Spores are spread by insects (such as aphids) and through the air. Even tiny vibrations from raindrops are to blame for spreading spores from leaf to leaf…and plant to plant.
High nighttime humidity creates a perfect environment to grow spores, and low daytime humidity makes for the perfect environment to disperse them.
There are multiple genres of fungi that cause powdery mildew to grow on peonies and other plants. Each one generally only affects one or two different plants – They will spread peony to peony or rose to rose. But….(there’s always a but!) there are few species of fungi out there that will cause powdery mildew on many different types of plants.
U-G-L-Y …You ain’t got no alibi!
Powdery mildew usually begins on the lower leaves. You may notice dry or discolored leaves long before you begin to see a flour-like coating on the topside of the leaf. The leaves may curl, dry out, or fall off.
The good news is that powdery mildew on peonies and other plants is more of an eyesore than a health problem. Really severe cases of this chalky fungus can weaken the immune system in plants, but in most cases, it does very little damage and does not require treatment.
Let nature do its thing.
Most professionals would agree that there is not much that needs to be done to combat powdery mildew. There are fungicides available, but they work as preventives. You need to spray before you find an infected leaf. Spraying after will help keep the mildew from spreading to other parts of the plant but will not kill what has already grown.
The easiest defense is to be sure that your peonies are properly spaced to increase air circulation. It’s also helpful to know that fungi survive the winter by clinging to leaves and other parts of infected plants. Cleaning up the fallen leaves can help lessen the chance of future occurrences.
In the video below Mike explains how he handles cases of powdery mildew on peonies and other plants in his landscape.
But, wait! What about dogwood?
Here is a video that talks about powdery mildew on dogwood:
I have been trying to find out more about the group that buys & sells from each other.
We bought your mist system.
What all do you offer?
See these pages, http://backyardgrowers.com/join and https://mikesbackyardnursery.com/2015/10/backyard-nursery-tools-of-the-trade-things-to-turn-you-into-a-successful-grower/
James R. Majewski says
There are two common myths about the peony. In one, the peony is believed to be named after Paeon, the Greek physician of the gods.
Kate O'Neill says
Thank you so much for this straightforward and concise take on powdery mildew on peonies! I am much relieved and love your down to earth manner and advice.
I have the white powdery substance on my peonies. Under the leaves when I cut them back are little bugs that are white….. and looks like many babies layer as well. Plus other little bugs that are white in colour with spots(a lot like a lady bug) but white and much smaller in size.
What is the best way to treat my peonies. I’m afraid the little bugs may be in the would surrounding the peonies where I had just cut them back.
I’d say that the bugs and the powdery mildew are not related. My approach almost always is to do nothing and let nature take it’s course. If these are a type of lady bug you certainly don’t want to kill them.
Mandy Evans says
Try need oil!!
I also have peonys with powdery mildew on the foliage. I should have treated it. I have cut the foliage off and stems off and bagged it up to go out with the trash. I am just wondering if the mildew would be in the last of the plant that is in the ground (roots) where I cut it off. Should I treat this?
I wouldn’t be concerned. Treating the plants next summer would be more important.
Thank you, Mike! I get powdery mildew almost every year in upstate NY on my lilacs. It’s ugly, but what are you going to do??
There are treatments but I usually just ignore it. https://en.wikipedia.org/wiki/Powdery_mildew
I notice and get that stuff on my peonies if I continue to water or if we get a lot of rain. Thank goodness only after it has finished blooming and only foliage left. When I see it- just cut it out and dispose of leaves – no composing!
Thanks Mike! You always give us peace of mind! ( gardeners tend to be a little neurotic!)
Linda Fairbanks says
This is the second year, maybe third, I have tried to get rid of the powdery mildew. My plants came from my parents place about 50 years ago, so I would like to save them. They are on the east side of my house, so they get full morning sun; they are watered in the early morning hours 3 days a week. Would it be beneficial to move them to where they can have more sun, and are they drought resistant even a little. Is the fungus in the soil. If I move them, how exactly do I take them and split them up and how deep do I plant them. It seems like Dad said that if I planted them to deep, they wouldn’t bloom.
More sun and air circulation will help, but they are prone to get powdery mildew.
David Magnusen says
I’ve had some luck spraying with Hydrogen Peroxide…
Jan Brownlee says
My peonies look like they are wilting – stems lying on the ground and they have what looks like powdery mildew on the leaves. What should I do? Are they dying? Help!!!
Not dying, just a lot of powdery mildew. I’d just cut them back and they should be fine in the spring. Don’t leave those powdery mildew stems laying there, dispose of them to help the situation for next year.
Nuella Luther says
I had a case of mildew on my fig tree two years ago, I made a mixture of Dawn and Water and washed the leave as best I could, If nothing else, I felt better. The tree is doing very well this year and has a lot of figs ripening now. I would love to start some plants from it but I need more information on that process.
Thanks for all the great information.
I don’t know much about figs, but I’d start here if I were you; https://mikesbackyardnursery.com/2015/01/easy-summertime-plant-propagation-techniques-can-home/
JL Sankot says
The powdery mildew doesn’t bother me, but I do have some type of fungus, or something, affecting my cucumbers. Brown spots on the leaves, which eventually turn fully brown and fall off. Had a ton of blossoms this year but, so far, only 4-5 cucumbers! Sorry to be off-topic, but this has really been bugging me.
I am having he same problem lots of vines but no cukes
I got a blight or something on my cucumbers, and it looked like they were done. However, I pinched all the affected leaves off, and they came right back.
i see you have replied to a couple of people already about cutting back the affected Peonies but I would like to know when to cut them back and how far back would you cut them?
During the growing season I would not cut them back too hard. I had peonies the landscape at the nursery and ever summer they got powdery mildew. I didn’t cut them back until late fall.
Mike, before researching this I cut my mildew peonies to just a little above ground level in the middle of August. Will they recover next spring?
More than likely they will.
Francis Sherman says
I forgot people grow Rose bushes also By grapes , bercause it hits the grapes after the Rose bush, then they know when to spray)
Francis Sherman says
I Added a link (pfaf Plants for a future )
I know for Growing grapes Bio Dynamics use Horse tail (plant) to stop Powdery mildew (which could affect harvest )
There are some interesting Fungacides like birch leaves
I know Tobacco was broufght up to prevent bugs
(I knosomething simlar is used called Neonictioidss (which causes bee’s to get Nerves systems to be disrupted )
PEople also use Tomatoe leaves for bugs(boiled with water ), and Rhubard leaves Simmered in water
On A grape breeders forum they try to breed plant that are resitent , Since Powdery Mildew IS not native to (Europe ) So those Wine grapes do not have resistance Like our natives (Norton is a good American Red Wine That is Bold , but I think even that hybrid may need a little spray that the Bordeaux spray is copper, and Sulfer, a nd can be used for Organics_it is grown in Missourri though)
I found an easy solution that works. After cutting off all the peony leaves last fall, I put about a cupful of baking soda over the soil in a pot the size of a half whiskey barrel. Then I mulched and waited til Spring. Completely gone. I was amazed and well pleased. God bless you all.
Thanks Sandra, great information.
Please explain in more detail?
Did just use baking soda? Or mixed with water? Please explain.
Linda Pannell says
Thanks for the input on this fungi, Mike. I have a huge lilac bush in my back yard with this problem, but the one in the front yard does not have this problem. The one in the back has lost a lot of leaves, and is an eye soar at this point, but at least I know what it is now. Both of these bushes are at least 20 years old. Thank you again for your input on this.
You are welcome.
I’ve gotten powdery mildew on my peonies for probably the last 10 years. I used to freak out about it, but it never seems to affect the health of the roots…they’ve been coming up every year like clockwork, for the 64 years that I know of. I don’t think I could kill them if I WANTED to…they take a lot of abuse, and never seem fazed.
And the powdery mildew seems to set on after the flowers are spent, so it’s not that big a deal, to me. It would be nice if that foliage stayed healthy all summer, but I’ve come to just accept what happens.
I tried cutting everything down for a few years, bagging the affected branches up and putting them in the trash, but it didn’t seem to change the amount of PM I would get the next year…so now I just cut them down when they get too ragged, and just leave them to rot where they are.
Also, they were hit with PM pretty hard this year, and it has been a considerably hot and dry summer here in Pittsburgh. So even when the conditions aren’t all that wet, it doesn’t seem to affect the amount of powdery mildew I get.
You’re right and that’s pretty much how I deal with it. It comes, it goes. Just part of how plants and other things work.
Etta Miller says
I Wonder why I have problems with what a I think is aphids on potted hibiscus. What is the safest method of control? Thanks
The safest control would be a spray of insecticidal soap. I’d give that a try.
Hi Etta & Mike. My11th generation Ontario Dairy farmer mother in law had this- AND WOW it super works for aphids. Spent cigarette butts in a spray bottle+ a drop or 2 of simple castile soap per gallon water repels the pest without damaging stalks, stems, buds, leaves or most any blooms.
Weird, because mosquitoes apparently LOVE smokers’ blood-but aphids don’t like nicotine.
Hi. That tells us a bit about the toxicity of the cigarettes! We are an organic farm and I would not like to use this tobacco remedy, perhaps tomato leaves would work?
Is tobacco really not organic? I was thinking it’s another plant. I really am just curious..
Of course tobacco is organic. It’s not exactly the safest or the healthy person can consume in any form but it is natural and organic.
melissa jean says
i’ve found that neem oil spray, with a couple drops of castile soap, sprayed on plant foliage eliminates powdery mould. it also repels aphids, caterpillars, and spider mites! :^D
it’s entirely natural and is completely safe for use in organic gardening/farming.
My peonies developed powdery mildew for the first time this season. Since they have already bloomed, should I cut the plant all the way down and hope for better luck next year? Or just leave it alone? Or spray with the milk solution? Thanks for your advice!
I’d just trim them some but not all the way down.
I am in zone 5 (Chicago) and have a community garden that harbors powdery mildew to say the least. It hits the squash leaves really bad as they are big and shaded at lower levels. My peonies at home have been getting it for a couple years now as well.
1-2 Tbs baking soda and 1-2 Tbs canola oil (as the carrier) per gallon in sprayer. Cut heavily infected squash leaves out to the vine…they aren’t photosynthesizing anyway covered in mildew. Drench the plant top to bottom – dripping wet. (Do not spray in midday sun of course… early or overcast is best) Tops and bottoms of leaves, stems, vines, soil within drip line as the fungus drips down and can harbor in the soil. Do it every couple days especially after rain. I believe the alkaline environment prevents the colonization of the fungus. I like to feed with a 5-1-1 fish fertilizer (and worm castings) the following day to help the plant bounce back.
Peonies should have leaves to make some energy for next spring so you want to save as many leaves as possible. Same mixture. Drench it and stay on top of it and it will go away. Works great for me good luck!
Thanks Mike you have a great thing going here! You da man!
That’s for the great information. Powdery mildew seems to be bad this year because of all the rain earlier in the year and of course lots heat brings a great deal of humidity as well. As usual my dogwoods have it but so far this year the peonies seem to be fine.
Do you mix the oil and baking soda into water or is it just those two ingredients?
This isn’t my recipe so I honestly don’t know. Somebody else provided this post for us.
Val Zudell says
I bought a yellow climbing rose this year and when I got it home discovered the lower leaves were covered with powdery mildew. I tried the baking soda remedy but it just kept spreading until I feared I would lose the plant entirely. I searched the internet to find remedies but nothing seemed to work. I did learn that the fungus is systemic. I finally decided to try using Hydrogen Peroxide 3% @2 teaspoons per gallon of water. I sprayed the plant first and ten dumped the remainder in the soil around the plant. That seems to have worked for me as I have seen no more evidence of any kind on the plant in the last month and now the plant is looking vigorous and blooming! I believe that this is because it was taken up by the roots and removed the fungus from the system.
Thanks Val, great information!
William Connor says
Yes, mix with water.
If you only mixed the two ingredients (baking soda and canola oil) in a gallon sprayer, you would go through over a half gallon of canola oil and maybe a pound of baking soda.
He said per Gallon so I’m sure he means to add to a gallon of water.?
I have heard of the baking soda remedy. In the past that hasn’t really worked for me. My peonies are also here in Chicago burbs and so far this year they look good. I have been watering them from overhead with aspirin water for the past month and more from below with the garden hose. Initially used 1 aspirin to 2 gallons water but now I’m using 2 aspirins per gallon and I think it all looks good. I also started using 1 part milk to 2 parts water all over both sides of the leaves. I look at them every day and if I see anything ugly, like a little black spot, or a black bud that didn’t open, I cut it or pick it off right away and get it outta there. I have heard that Castille soap works well, so I’m also going to start using that. Canola oil is another one to try, and lots easier and cheaper than neem oil, which I used last year but it didn’t work well, but oil makes me nervous because these peony bushes receive a lot of afternoon sun and I’m afraid I’ll cook them. About the alkaline theory…people also use apple cider vinegar and that is acidic, as is the aspirin water. The thing I am most curious about trying is Folex carpet cleaner (diluted). It is a non-ionic surfactant and I’m wondering if it would be a cheaper option than insecticidal soap. I might experiment on a few zinnias just to see what happens.
I have powdery mildew that develops on my zucchini and summer squash leaves. Not very attractive, for sure. I have been picking off the infected leaves but it doesn’t leave much of a plant! Glad to hear I don’t need to do this anymore until disposing of them at the end of the season.
Damon Hague says
I have consistently enjoyed your articles. you. I have plants indoors that have a critter of some sort on them. It looks like little pieces of cotton. I have sprayed with alcohol diluted with water, that removes them for awhile then they return. I have them on my Amaryllis, Kaffir Lily, Xmas cactus and orchids, Do you know what this is and how to get rid of it. Sincerely, Damon Hague
It sounds like you could have mealy bugs. Here is an article that might help you:
Yes that is definitely mealy bugs
I’ve got powdery mildew on my lilac bush I planted this year. But I’m encouraged that its not anything to lose sleep over. Thanks for your continual flow of great info!
I am wondering what the green very low growing plant is on the ground near (behind) the peonies. Very flat and looks like its just sprawling on the ground. I think it’s very neat looking.
What is the name of it please?
Thanks Mike and I hate the powdery mildew on my plants; glad you had this video to watch! Thanks for your time and energy it takes to video these things!
Have a great day!
The green spreading ground cover you see behind the peonies is blue rug juniper. That particular one is in need of some pruning, but I kind of like the starfish look its taking on.
I find black mildew, or mold on the back of my Basil leaves. Anyone know if the same solution will work on this? It is on the underside only.
I read your newsletter whenever I can & enjoy it so much. Recently you told us to save or use coffee grounds. I’ve been saving them & now can’t find where you told us what to do with them. Please help. Thanks
I had powdery mildew on some peonies last summer and this year that same plant did not come up. The mildew was so bad on them they were black and fuzzy. I have to admit that they were planted in a pretty shady location but, to have them not come back this year makes me wonder if this mildew is more harmful that we think.
Any thoughts on this? I love my peonies…some of them are from a plant that my family has divided for over 80 years and were started by my grandfather. This one “was” a Karl Rosenfield peony….the last of my reds.
Its sounds as if you might have had a case of Botrytis or Phytophthora Blight. They tend to get a dark gray or black fuzz and cause cause root or crown rot.
Thank for your reply. It has spread to nearly all my peonies now….the whites and pinks are also all fuzzy. Very concerned I will lose them all. Even a few new varieties that I bought this year have it. Anything I can do that is safe for them?
This phytopthra moves through the soil. If you have some of your valued plants that can be lifted, you can clean their roots and disinfect them and then plant somewhere else that is far from the infected area. We have a problem in our orchard and of course we cannot move the trees around, but the information may work for you.
Ellell Ess says
Thanks for this blog. Every year my Lilacs develope this powdery fungus and I dutifully fill my sprayer with vinegar, oil and dishwasher liquid. Each year I tell myself that I am going to have to destroy this thing. Each year leaves start off without the fungus and the lilac produces fragrant blossoms. I am going to stop thinking about destroying the plant and start fully enjoying the best of the plant.
this is the first year i’ve noticed it on one of my Lilac bushes. I’m going to give the vinegar solution a go, see what happens. Thank so much 🙂
RONDA STEELE says
I have found a simple solution to powdery mildew–and it works on laundry too! Have you ever left a load of washed clothes in the tub too long, only to discover a “mildew” smell in your whole load of laundry? The solution for that problem is related to outdoor powdery mildew too–vinegar. I add about 1/4 cup of white vinegar to the rinse cycle of my wash, and even days after being left in the tub–no mildew smell. So I applied the same solution to the outdoor nuisance: diluted white vinegar with water in a spray bottle with a small squirt of liquid dishwashing soap (to help it stick to the leaves), sprayed directly on the affected plant/tree. (it’s quite harmful and common to new growth on apple tree leaves). It does need to be applied weekly to kill the mildew, but make sure to dilute the vinegar about 1 part to 10 parts water so it doesn’t burn the leaves.
Toshimi Minoura says
Mix one part of milk adn four parts of water, and spay the mix on leaves.
I was told that it works better than any commercial fungicide, and it ddi.
I have what I think are spinder mites on my Jade plant. It is sticky puff ball that causes the leaves to be deformed and die. Please help me.
Best thing is to search online to make sure it’s spider mites. It doesn’t sound that way to me, but I could be wrong. Try searching pest identification or jade plant fact sheet.
I understand that no real harm is happening to the plants with mildew, but, some of us are perhaps more concerned about mildew, just because we want our gardens to look nice for various reasons. So we make various efforts to deal with the mildew. One of the problems I have is that lets say I know it is time to put on a biweekly treatment of some kind, but it rains off and on and I can’t find a time when it looks like things will be dry or when it will not rain in the next few hours.Should we go ahead anyway and put down whatever we normally spray with?
I think if you have a few hours of dry weather an application is sure to help with the problem. I don’t bother because I have so much else to do and plants that are prone to powdery mildew are prone to powdery mildew.
My peonies are free of mildew and finished blooming long time ago.
But one of my cucumber plant has already couple of leaves infected and it still has several
baby cucumbers (planted in a container)
Anything needs to be done?
I would search cucumber fact sheet and you’ll probably get good information. Keep in mind, you have to be really careful spraying food crops.
Helen Penn says
Very glad to read that powdery mildew isn’t an issue. My peonies have been getting it for the past two years and I just keep cutting the stems back. These are special to me because they were in my parents’ garden for many years. Thanks for the information.
I understand. It’s my experience that some years it’s an issue, some years it is not. That’s why I don’t worry about it.
can this affect dogwoods? ive been having issues with mine-esp the verigated ones
Absolutely and the variegated ones are even more prone to it. You can try treating them, but I don’t. I just hope for better conditions next year. Just rake up the leaves under the tree in the fall and dispose of them.
I have powdery mildew on my peonies for the first time this year, and I’ve had them 20 years or so. Would it hurt to cut them back to get rid of the unsightly foliage in the middle of my perennial garden? I don’t want to lose them. They came from my mother-in-law’s garden and she has now passed away.
I’m sure it will do no harm, I just trimmed mine last week.
linda sinna says
I like to email articles to my daughter. Why don’t you have email for a choice?
If you just got to the address bar at the top of the page and copy and paste the web address for the article, the URL, you can simply paste that into an email to send it to a friend or your daughter. Thank you for sharing my articles!