Question
Why do my Zinnia plants (leaves) get all white at the end of the growing season?  That would be around the end of August and September.  

Thank you, Linda

Answer
Linda, the same thing happens to most of the varieties I plant. Zinnias are very susceptible to a disease called powdery mildew. The symptoms are much like the description; a white powdery substance that covers most of the foliage.

The good news is that it can be prevented. The bad news is that it is costly and not practical. You can spray the plants every 10 days starting in May with a copper-based fungicide. This will prevent the spores from multiplying. However, given the fact that this disease strikes at the end of the growing season, and that fungicides are not cheap, I usually enjoy my zinnias through the middle of August and then let nature take its course.

One other option is to grow a new hybrid that was released four years ago called Profusion Zinnia. This cultivar is resistant to powdery mildew, and like its name, is profuse in the number of blooms it produces. I grow these in my front bed and get compliments every year.

Unfortunately, you will not find these as seedlings in many of the gardening centers. Instead, you have to grow these from seed, which can be purchased through either of the following companies. Just type Profusion Zinnia in their search field and you can choose from several colors.

http://www.parkseed.com

http://www.burpee.com

I hope this information helps for next season. Good luck, and please write again if I can ever be of assistance.

Regards,

Mike