Powdery mildew is usually a response to environmental conditions like leaf trauma, dryness, excessive wetness.

its fall ... its time to watch plants get real ugly ... its not time to keep battling ... its all down hill from here ...

you would cut them down ... perhaps treat the stubs one more time [full fall cleanup, removing as much potential for wintering over spores to start it all next year] .. mulch them for winter in a month or 3 ...

and see if they over winter ...

next spring.. if they are dead.. you move on ...

if they are alive.. you either kill them.. because you werent happy with their performance... or move them somewhere else .. perhaps where there is more air movement.. and hope they do better next year ... and if they perform the same next year.. just kill them ... they had their chance ...

or you just get rid of them now.. because you are fed up with them ...

the hardest lesson for a newb.. is understanding that summer is over ... lol ... its all downhill from here ... and second ... if its a bigger problem than its worth.. get rid of it ...

ken

ps: just yesterday.. we cut down a swath of tall phlox at moms.. due to heavy PM ... we didnt care if timing was right.. bloom was over.. God knows we dont need more seedlings .... and the PM was ugly ... they wont die from being cut back to 3 inches ... we only wish.. lol ... its fall .. time to cut bait and be done with ugly things ...

Dinah, re the home-made solution, I don't see the point of both baking soda (used to create a more basic/alkali environment) and vinegar (typically a weak solution of acetic acid).

I believe that a baking soda solution (as above) prevents/ limits the spore formation (hence spread) of the powdery mildew fungus.

This is a very bad year, here, for powdery mildew on garden phlox. Kevin notes a similar problem too. It's evident that bad years come periodically with garden phlox. The powdery mildews are apparently species specific, so they spread from one kind of plant to another.

My response to powdery mildew has always been manual. In future, I may try spraying with a 10% milk solution (washes off with rain, so need to reapply). This has proven effective in controlling powdery mildew on several agricultural crops.

I'm a very firm believer in garden hygiene/sanitation. To me, treating a garden like it was a natural ecosystem is silly; notably, if you have a small property and a traditional flower garden.

I always cut back and thin out the garden phlox (and all other perennials we have) as soon as possible. I always cut all herbaceous plant material down to ground level and remove all plant debris before winter.

Otherwise, especially with our precise location and style of perennial gardening, we'd be providing winter accommodation for undesirable elements such as powdery mildew.

To restate what some of the folk above say, powdery mildew is one of the stressors many types of plants face. Some types of plants obviously have more of a problem with it than others. Nevertheless, a plant weakened by other environmental stressors is less likely to be able to fight powdery mildew off.

This post was edited by SunnyBorders on Mon, Aug 25, 14 at 12:19

Thank you so much for your responses.

SunnyBorders, to answer re: vinegar & baking soda, the site where I got this formula acknowledges that they cancel each other out but together they produce sodium acetate and this is apparently the active ingredient in mildew inhibitors.

I will try without the vinegar, unless I take Ken's advice and give up on any treatment this year.

I am alarmed at what you wrote about the mildew spreading to other kinds of plants, yet you wrote that it was "species specific". It was my understanding that it would not spread from the coreopsis plants to the other perennials in this border. Could you clarify that for me please?

I think I'll visit the local nursery and get their recommendations about whether to treat at this time of year or not. There are so many conflicting pieces of advice on the internet, that for a 'newbie' it is confusing.

Add to this, that this is a border for a condominium complex that I undertook to establish this year. I don't want to risk losing everything and take the heat. If you know anything about condo living, you will know what I mean. :-)

I appreciate all of your advice and points and I am taking everything under consideration.

There are two problems that are guaranteed to happen with certain plants every year here in my climate when it gets hot and humid -- red spiders or powdery mildew. I eliminated both problems by banning plants that are prone to either, otherwise its a depressing annual loosing battle I have no desire to witness or wage and besides, there are so many other choices of plants not prone to either. Sometimes powdery mildew is a matter of air circulation, for example, I know crepe myrtle will get it if its planted in a closed in spot like a courtyard but will do just fine planted in the open but with other plants, such as coreopsis or phlox, it doesn't matter, they get mildew no matter what. Since neither of these are high on my list of desirable plants, its easy enough to live without them.

Blanket flower does just fine for me. Much better choice and more blooms and the seed heads are also decorative once they are spent. I prefer the annual kind because they are blooming machines compared to the perennial types but those are nice too.

I would add that coreopsis are early season bloomers. Some plants tend to look like crap the rest of the season after blooming while others produce and retain nice foliage. If you grow a variety of plants in an area, this is not such a problem but if you want a bed to keep looking nice all season, choose plants (such as dianthus) that will still have nice foliage once the bloom time is over.

This post was edited by TexasRanger10 on Mon, Aug 25, 14 at 14:38

TexasRanger - thanks for your input.

I find coreopsis to be a long bloomer in our climate. My Moonbeam and Zagreb are blooming profusely right now and have all season. I suppose it depends on the growing conditions and not on the species? On the other hand, the dianthus we have look like crap, as you said, after they finished blooming.

My border includes Coreopsis Zagreb, Campanula Carpatica, Bloody Cranesbill Geranium, Silvermound Artemsia and Spilled Wine Weigela, along with the Baby Sun Coreopsis. So, I feel that I do have a good variety of plants in this bed. All other plants are established and healthy and doing very well.

I am strongly considering Blanket Flower to replace the diseased plants next year. Thanks for the testimonial.

Interesting. I always keep in mind that what I read here is regional. Most advice is not applicable to us here since it seems like most posters live up northeast and so many of their plants are not good choices here but I often get some good laughs because they as well be living on a different planet, many plants they deem disappointing or difficult look great and are easy to grow here so it all evens out. Dianthus is a pretty thick mound of glaucous blue year round here, gorgeous in winter, in fact I like it best when its not blooming, its quite drought tolerant so maybe you get too much moisture? Moonbeam did terrible for me, the double types look good while blooming but then they mildew later while the common lanceleaf are just boring green leaves once they bloom in spring which means 95% of the year, not worth the space they take up. I use them in what I call no-man's land just because they are so prolific and will come up ANYWHERE.

I live in the Okanagan Valley, Pacific Northwest (Canada). We have a unique climate for this far north (very hot and desert-like in summer) with very little rainfall.

To each their own when it comes to plants.I happen to love the Moonbeam and the Zagreb Coreopsis, so go figure.

This lanceleaf variety of coreopsis was sold at our nursery as a bloomer from summer until fall. If it's only a spring bloomer, I would never have chosen it. You can't seem to rely on information on nursery websites.

I agree with your comments about regionality re: advice and choices. Thanks for taking the time to answer me.

Interesting about sodium acetate in mildew inhibitors, Dinah.

It would not as you say.

Your 'Baby Sun' is a cultivar of the species Coreopsis grandiflora, so it might spread to say C. grandiflora 'Sunray' or C. grandiflora 'Early Sunrise' (both members of the same species), but certainly not to say any garden phlox cultivar. Phlox paniculata is not only not related at the species level, but it's not even in the same Genus.

I too have found various Coreopsis grandiflora cultivars to be very long blooming (all summer) here, though I've always deadheaded them to keep the bloom display up.

I'd say Ken recommends manual treatment, not no treatment; namely cutting down and removing plant material from the flower bed. Personally, I wouldn't be leaving any part of any herbaceous plant above the level of the soil over winter; especially all plant debris, infected or not.

We all have different philosophies and approaches to gardening. I live in an area of distinct seasons where a large variety of perennials grow very well. I also garden for blocks of flower colour and want the colours to change throughout the growing season. Consequently, I strenuously avoid planting any seeder or runner that could "come up ANYWHERE". But why should we all try to garden in the same way? TR's and my posts make it clear that we don't.

I believe that that spraying a 10% (aqueous) solution of milk is based on quantitative research on commercial crops; but it's treatment, not prevention.

Crossed.

Re Coreopsis lanceolata.

Here it does as equally well as C. grandiflora.

I had C. lanceolata 'Sterntaler' growing with the C. grandiflora cultivars, mentioned above, for years. They were in, what is for us, a hot dry neglected location; but all of the cultivars did equally well.

If not the Okanagan Valley, Dinah, I have been to Kamloops, B.C., so I do really appreciate how not all hot dry summers are the same!

Heat shuts a lot of blooming down in summer here. Some plants, like coreopsis will die down to the ground and go into summer dormancy or just croak without constant watering. Even with watering, its mainly a quest to keeping them alive, forget about the appearance or blooming. Obviously the heat loving plants such as muhly grasses, flame acanthus, lantana & salvia greggi do great and love it. The more heat, the better with certain plants.

We have a very long growing season compared to further north so this factors in to what I consider long blooming period. Our spring is more like summer up north and if that lasted all summer, coreopsis would bloom all summer, as it is they bloom from April to mid to late June, get mildew then start to die down to the base leaving a big ugly hole. In fall, new leaves start up that stay pretty much evergreen. Its not a fair comparison but to my mind, thats a spring bloomer.

Plants that resent a lot of winter moisture with freeze/thaw cycles do quite well here too, we don't get that heaving that I have read about so there in not the need to mulch so much unless its a 'zone stretcher'. Plants for the most part are much much easier to get through winter than summer.

As far as mold or mildew is concerned, it's caused from spores in the air, usually in June when its most humid, not passed from plant to plant as I understand it. Plants do not need to be planted side by side "to get it from each other" because some types of plants are susceptible while many others are not, its not what I think of as contagious. Same with red spiders. They don't care if its marigolds, ageratum or tomatoes, its all the same to them.

This post was edited by TexasRanger10 on Mon, Aug 25, 14 at 17:39

I agree, PM is ever present in the environment, unless you're gardening in a bubble.
I'm not even sure if there are different species of PM or it's all just one :)

However, I know they recommend garden tidyness, and removing clippings, etc....but I, like TR, live in a hot dry place and we mostly let our plants fend for themselves with regards to intense grooming (other than shovel pruning or it's equivalent). I don't usually see my plants sneezing on each other and spreading disease..but then I garden as 1 or 3 or so of this, and 3 of that...so maybe there's little risk, being species diverse patchwork.

barron, all I know is when its reported to be high and the plants that the mildew favors as hosts start getting the white mange, I coincidentally get that annual summer "cold" & cough otherwise known as allergy season symptoms. Its always when the mold count is high that all this business happens, maybe I am catching it from the plants? Nah, its in the air, the weatherman sez so. With some people its grass, for others its tree pollen.

However there is that new rose disease going around Oklahoma laying a lot of the roses, especially the 'Knock-outs' low, and they do catch it from each other. You have to take out the affected plants to deal with it before it affects the others.

Yes, TR, I've been teasing a friend in OKC about having to remove her dear infected roses. I keep telling her there are so many more interesting things to plant that aren't so finicky and disease prone :)

They over planted those knock-outs here to the point of gag. Its just nature fighting back, thats all.

Here it is spring again and my Coreopsis (Zagreb and Baby Sun) are both beginning to come up. I cut them to the ground in fall and cleared the area around them of all debris, sprayed them and the area with a good dose of my homemade recipe. The PM last year on both plants was established when I began spraying with this recipe. As I knew, it did not kill the PM, but it did control it and keep it from getting worse.

My question now is - should I begin spraying them now as they begin to grow or wait until ? Our garden centre carries Safer's Sulphur Dust and Safer's Defender Garden Fungicide for PM. Has anyone had experience with these products and are they harmful to coreopsis? I am considering them as a better alternative to the Internet recipe of baking soda, soap, veg. oil etc.

Thank you for any and all advice.

p.s. I live in Western Canada and Neem oil is not available.

I have used baking soda/water and sulphur dust. The suphur can be mixed with water or sprinkled on. Since you know it is a preventative measure as opposed to curative I would start early.

Here we would start late May early June. You need to start earlier but I would be concerned about the tender new growth being more susceptible to burning. Either way you cannot apply when the temperature is high 24-26 C that is approx. 80 F as it will disfigure the foliage. Read the label for exact temperatures and plants that the product should not be used on.

Knock on wood. I have had PM on Phlox but never Coreopsis.

Latter, me too; never seen the Coreopsis one.

Knock on a non-woody plant.

Thank you so much peren.all for your valuable info. If I may ask, have you experienced burning at any stage of growth from either of these solutions? I too am concerned about harming the tender new growth.

Our summer temps. are very hot during the daytime so I will have to be careful if I use a commercial product. I didn't find this to be a problem last year using the baking soda/soap/oil/water solution, even when it was over 30 C here. Maybe I could alternate between using sulphur below 24 C and the homemade solution for higher temps.

Any further comments from yourself or anyone else are so appreciated!

p.s. I had PM on my Phlox too :(

Interesting thread. Question to Perenall...is it a given that the mould will reappear? My first thought was...do nothing now, wait and see....primarily to protect new growth. What happens one year may not reoccur the next..? You grow a large variety of perennials and I am curious if you've ever experienced recurrence.

I haven't heard of mildew on coreopsis before, but phlox, yes. Air circulation is key when growing phlox. If clumps are very mature thinning some stalks selectively enhances air circulation. I have them growing in various locations, dry/hot/sunny, eastern exposure and northwest...had mildew only once in northwest locale, but it did not show itself since. I have no answer as to why...weather related perhaps. Hacking/snapping off unsightly stalks is quick and easy as it produces more shoots quickly (also thins out a vigorous-growing perennial) but that doesn't solve the problem if mould is a recurring issue.

I had Moonbeam coreopsis which grew well for two seasons, then died. That was a winter where voles took up residence in a front bed. Zagreb is 6+ years old, is fantastic, growing in a hot, dry but windy corner. It even flowers sporadically until frost.

Interested in your viewpoint and experience, Laurie. :-)

Jo

Thanks again peren.all. I'm enjoying all of the comments and learning so much from everyone! You mention Blanket Flower as an alternative and I've read quite often that it is such a great plant. Yet, when I research it more I keep reading how "messy" it is. Is that true of all varieties? I have been looking at "Candy Corn" and "Dazzler". Do you have one that you recommend over others - especially looking for one that isn't a messy grower. That wouldn't fit into my border. tyvm

Oh, p.s. Does Blanket Flower from a nursery bloom the first year? This is very important as the C. Baby Sun didn't bloom in its first year last year and I have many eyes upon me as I try to establish this perennial flower bed for our condominium. (what was I thinking? lol)

dinah C. 'Baby Sun' should have bloomed first year so hopefully this year it will perform beautifully. They usually bloom first year from seed.

Gaillardia (Blanket Flower) should also. 'Goblin' is one I have grown for many years and it is a prolific bloomer. It is very compact, under 12". There is 'Golden Goblin' but I have not grown it. So many new intros have come onto the market and time will tell if they perform as well.

There is a miniature Daylily that I would recommend. 'Penny's Worth' blooms all summer long. It will take a break for a few days here and there but it continues to bloom even after snow has fallen. It is also under 12".

I think you should give your Coreopsis a chance to prove itself but it is nice to have alternatives.

Daylily 'Penny's Worth' is in the centre of the pic.