I read about a home-made solution with baking soda, water, vegetable oil, soap and vinegar and have started spraying them with this once a week. I know it won't cure them, but hope to keep it from getting worse.

Would you over winter them after cutting off all of the foliage this fall, in hopes that they'll grow back healthy next year? Or, would you dig them out and replace them with another perennial ... I'm thinking of Blanket Flower.

Thank you for any help/advice you can give me!

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 ...

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.

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.

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.

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.

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.

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.

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!

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.

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.

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.