I have used garlic spray to good effect on mildew (though not on verbena bon). I just soak a bulb of garlic in a pan of water for 24 then whizz it up with a hand whizzer, strain through cloth, put the liquid in an old squirty bottle and use on plants. Keep the bottle in the fridge. Garlic spray was great on dahlias, though I had to reapply about once a week. Rains now make that process trickier.
I think it's best to accept that that's just what VB does in dry conditions. The upside is that you get plenty of seedlings - often more than you want! In wetter, cooler conditions, mildew is less likely but so are self seedlings.
@Fire Wow, that's dedication! Here in Devon we seem to get lots of rain - maybe it washes away the mildew?? @B3 I'm still too much of a newbie to know about seedlings, will need to look into it. I'll just be happy if the verbenas are happy when I plant them in the garden next year.
@susiebower I also grow V Bampton which is lovely all summer and still looks good now, it is also indiginous. I will have hundreds of seedlings of both possibly too many for some. If you have just one plant and it is mildewed no need to throw it out the seedings from it will form the new future plants. As you are growing in pots they may appear in the gaps in your path or patio otherwise keep a look out in the borders nearby as they are tiny at first. In the spring they will regrow at the base cut right back to ground level and you are ready to plant in your border.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
And powdery mildews are 'species specific' ... there are different sorts for different types of plants ... so the powdery mildew on my roses will not spread to my pelargoniums ... but they may well get their own sort, if the pelargonium powdery mildew spores are in the breeze.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I do it to rescue hard won dahlias. This is the first year I've had big problems with mildew. Despite all best efforts at watering, the hard summer in south hammered plants that need lots of water, like dahlias. Borage gets it badly too. The garlic spray is supposed to be good against aphids too.
I have to say that I have never had mildew on verbena bon. I have it in a 'no watering' dry, sandy bed and it's doing wonders this year - healthiest ever, driest ever and tonnes of seedlings. I pot them up for neighbours - it's one way to spread colour and food for pollinators without having to do much work. I love seeing it popping up in the pavements and roadways of the neighbourhood.
I've never had mildew on V. bon, and have grown it for many, many years, but we also don't get much self seeding because the conditions don't suit. Even mature plants don't always come through winter, although if we keep getting 'non' winters like last year, that may change. I hope not - I like a proper winter, even if it means more expense on the heating.
As myself and @Dovefromabove have said- mildews are specific to their hosts, so you don't need to worry about it spreading to a different plant species.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
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In wetter, cooler conditions, mildew is less likely but so are self seedlings.
If you have just one plant and it is mildewed no need to throw it out the seedings from it will form the new future plants. As you are growing in pots they may appear in the gaps in your path or patio otherwise keep a look out in the borders nearby as they are tiny at first.
In the spring they will regrow at the base cut right back to ground level and you are ready to plant in your border.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I hope not - I like a proper winter, even if it means more expense on the heating.
As myself and @Dovefromabove have said- mildews are specific to their hosts, so you don't need to worry about it spreading to a different plant species.
I live in west central Scotland - not where that photo is...