Do you have gardening questions for Dear Ann [Bartlett] (the MASTER! GARDENER!)? Email them to email@example.com with GARDENING QUESTIONS in the subject line!
Dear Ann [Bartlett] (the MASTER! GARDENER!),
I had a funny year for zinnias last year. They got what looked like a fungal rot, like black spots and holes, then died. Then the next year they didn't volunteer in any number, the way they usually do. Have you ever heard of such a thing? (I reckon you have, you being a MASTER! GARDENER! and all.) I've been growing zinnias since I was a kid because they're so easy and trouble-free. I feel betrayed!
And while I’m bitching about the fecklessness of flowers, you got anything to say about cosmos? I had always thought they were easy summer flowers like zinnias but after two or three disappointing summers, I figured out that maybe they were supposed to be fall-blooming like asters. Why doesn’t anybody tell you that? I expect it’s some kind of government plot.
--Crouched in Flowerbed, Mumbling Bitterly
Carefree as zinnias are, they are quite susceptible to a couple of fungal diseases. You've described Alternia zinnia. Unfortunately, this fungus can remain in the soil for up to two years and infect the seeds of affected plants. Next year start with fresh seed and a new sunny site. Avoid overhead watering, and your zinnias should be as wonderful as ever.
Cosmos are another trouble-free classic annual flower. Easily started from seed, they love heat, sun, and lean soil. They are day-length sensitive and so flower more as the dog days of August shorten. It can be wonderful to have something in full flower as many summer bloomers are past their prime.
Best of luck next year,
--Ann [Bartlett] (MASTER! GARDENER!)
Native Californian Ann Bartlett never lets a lack of experience with a plant stop her from trying it in the ornamental beds around her home.