It looks like powdery mildew and it will spread to the rest if you don't do something. You need a fungicide for powdery mildew. If possible you could pull the most infected and treat the rest. At least pick off those infected flowers. They won't do anything anyway and discard them in the garbage. Clean up any debris in the bed and treat it the same way. When you water don't wet the leaves. Water the soil not the plant and never let your plants go to into the cooler night wet. That's a sure way to get powdery mildew

since its potted.. isolate it ...

i was under the impression that baking soda and water can take care of PM ...

and to be clear ... dont spend 20 bucks on a cure for a 5 dollar plant... just throw the darn thing away ... lol ...

and to be double clear ... even if you stop it.. it doesnt go away .. so it isnt going to get any pretier than it is right now .. unless new unaffected growth can cover it up ... which brings me back to... just throw it away ...

and one key for me was.. NEVER wet the leaves in the evening ... as with any mildew... they thrive in the dark .. with dampness ... i used to SHOWER everything after work ... created a mess ONE YEAR ... lol.. then i learned to water without wetting the plant... or doing so in the morning ...

ken

Thanks for the info. I'm really confused how it got this powdery mildew. I water only at the base and live in a very hot and dry climate. We're experiencing a drought and it's been in at least the 90s throughout the night the past month and well over 100 during the day.

I guess it's going in the garbage, as I don't want my other annuals to get infected. I have petunias, calibrochoa, and portuluca all in the same container.

Hi jordanmichelle,

I agree that the photos look like a bad case of Powdery Mildew.

" I'm really confused how it got this powdery mildew. I water only at the base and live in a very hot and dry climate. We're experiencing a drought and it's been in at least the 90s throughout the night the past month and well over 100 during the day. "

Whenever the subject of Powdery Mildew comes up, someone usually suggests wet foliage as a possibly causative factor. It is a popular misconception that water on foliage promotes Powdery Mildew. The truth is the opposite -- water on foliage can actually fight Powdery Mildew. Powdery Mildew thrives on dry foliage, and when it cools at night it gets the cool dry conditions that favor it. By watering only at the base you were following the advice of those who identify wet foliage as a cause of PM. Unfortunately, they are wrong. Some foliage diseases are favored by wet foliage, but Powdery Mildew is not one of them.

ZM

JORDAN!!!!!

such are the mysteries of gardening ...

you try again next year ... and if it happens again.. you simply quit growing that plant... usually because it hates you ... lol.. we all have a list of plants we gave up on ... it just gets to the point.. where it isnt worthwhile to bang your head on the wall ...

you read up on PM ... all of its cultural aspects .. and figure out.. which one you might be failing in ... such as wet leaves [dry leaves].. hot muggy nights in your micro climate ... lack of air circulation ... etc .. we can talk about it all day long.. but it is your garden ...

but as i said... sometimes you just give up on a plant .. not just this year.. but forever ... e.g. i gave up on tuber dahlia.. because here in MI.. i got sick and tired of digging all the tubers up every fall.. and storing them in the house ... same with canna.. etc ... it just wasnt worth the effort ...

ken