Brown spots on zinnia leaf
I have several varieties of zinnias growing. Some started indoors and some direct seeded. After reaching 5 feet tall, they developed small brown spots on the leafs. The spots have grown with the leaves and gotten slightly worse. I have attached pictures to this email.
The zinnias are growing in the south-facing bed and are watered by my sprinkler system.
I'm wondering what to do this year, but, more importantly, what to do next year to prevent this?
Thank you so much for your time!
El Paso County Colorado
Thank you for your question and pictures. How much time of full, direct sunlight do they receive each day? How does the soil drain in that spot? Does it hold water and moisture; does it drain out right away?
Note (for next year): Zinnias prefer good air circulation. They don't like crowding. Good air circulation reduces foliar diseases.