Powdery mildew, sorry. A difficult or impossible thing to control in overly crowded conditions.

thin it and remove all powdery mildew, and cross your fingers. You can spray Hydrogen peroxide on it to try to fight it. You want the Hydrogen Peroxide for food. 35%, not from the drug store.

I'm afraid that you will have to do more than thin your plantings. The PM affected plants will need to be removed entirely.

Spores can remain present long after the plants have been removed, so do don't replace with the same kind. PM fungi comes in many, many strains and these are specific as to the plants that they can infect. In other words, some of those plants in the crowded grouping are perfectly clean.

Use sharp snips to remove the infected plants at the soil level.....don't try to dig them out.

You cannot use the undiluted peroxide on your plants. Perhaps Laurie could explain how to mix it and apply it, since there will be no directions for this use on the label.

OR, you could try a commercial fungicide labeled for PM control, or Neem oil.

what they said ...

did you make the basket.. if so. the lesson would be ... couple of them ...

its overplanted ... a bit of instant gratification early ...

second ... because there are so may plants.. i suspect the only way to water it is by wetting everything ... and i bet you water in the evening????

in my MI ... mildew is a hot humid still night phenom ... exacerbated by wetting plants after dinner and making them go into dark with wet leaves ...

to devcrease such ... since you have no control over wind ... you thin the planting ... so what little air there is can move thru the plant.. and you water in the morning .. so the plant is fully dry at dusk ...

way back in my learning curve.. i would come home and water all evening long.. very meditative after a hard day at work ...giving everything a good wetting.. soil and leaves.. and learned real fast about PM ...

this is when i learned.. on the ground.. to use a breaker bar .. see link .. available everywhere ... and only watered the soil in the evening ....

the simplest solution is baking soda in a windex type bottle ... or a better hardware store one ...

but to start.. i might cut everything back to about 3 inches.. then spray it down .. top of leaves.. bottoms.. everything.. then move it to bright shade for a week since you slathered on the BS .. lol .. the soda... and see how it responds ...

an experiments always teaches you something for next year.. rather than just throwing it away now ...

BTW .. i see a lot of seed pods on the petunia.. they need to be removed.. or the plant will go in decline anyway.. and the easiest way is to just prune back hard ...

ken

The peroxide is a good idea. I've used a 10/1 water/peroxide spray when starting seeds indoors, it prevents damping off, which my zinnias tended to do. You could also try a mix of baking soda and water as a spray, I've used that too, on my peonies and it was helpful. Its especially good for the veggie garden, safe and no toxic chemicals.