Expert: C.L. Fornari - 7/3/2007

Question
Hello....
I live in Michigan, and this Spring I decided to plant Marigolds in a flower bed around my driveway. I planted them around Memorial Day weekend. They are the the tall yellow ones with the big heads. They took off and did very well. Now I've noticed that some of them are getting a film on them. Then the leaves with the film get brittle and the plant eventually dies. I've lost several and more are getting the white film. I'm afraid I'm going to loose them all. I have several sprinkler heads located in the flower bed and I keep them watered daily. What I'm I doing wrong?

Thanks for any help you can provide.

Answer
Vince,
Marigolds are flowers from Mexico, so they prefer long dry stretches...in fact, most plants want a deep soaking less often, not a sprinkling every day!  Frequent water on the foliage is a perfect recipe for leaf spot fungi and mildew, and it sounds like you have powdery mildew.

Water marigolds for a long period once a week when the nights are below 70 degrees, and every five days when the temps are very hot.  

At this point, alter the watering right away.  Also, you could spray the foliage with baking soda mixed in water (two Tbls per gallon) or a product called GreenCure (a super baking soda - available in garden centers)   Spray in the morning so that the foliage drys.  Baking soda slows the growth of mildew.
You should only have to spray once.  Cut off spent flowers and give them a mild application of a liquid fertilizer.

I hope this helps!
C.L.
C.L.