Expert: Long Island Gardener - 7/16/2011

Question
my hydrangeas in Lido Beach had wonderful, colored blossoms until recently. Now some of them have blossoms drying and like rust. I believe they have plenty of water and sun. Other hydrangea that get less sun and less water are fine. What can I do for the problem?

Thanks for the time,

Steve Jacobson

Answer
Hydrangeas are susceptible to several common ailments.  Do these photos resemble any of the symptoms you see in your own shrub?

www.aces.edu/pubs/docs/A/ANR-1212/ANR-1212.pdf

Insects can also be a problem. In my experience, with the dry weather we have been having and the heat, it sounds to me like you have a spider mite problem.  Inspect the undersides of the leaves closely and see if you notice any tiny moving dots the size of the period at the end of this sentence. They are easier to see with a magnifying glass.

Here's something I've posted about battling spider mites and what you can do about it:

www.helium.com/items/1313330-spider-mite-control

In a nutshell, I have found Ladybugs to be the perfect predator. Easier than spraying up and down the plant over and over, repeating after rain.  You can pick them up at your local garden center; Hicks sometimes sells them; and they can be ordered by mail.  Gardener's Supply Company practically certifies their Ladybug stock to be free of disease and guaranteed to eat all the mites.

What keeps them on the plant?  Look at it this way: If someone puts a silver platter in front of you with a Porterhouse Steak, and you haven't eaten in a week, are you going to get up from the table and walk down to the Post Office for dinner?

That's how the Ladybugs see it.  Spider mites = Porterhouse Steak.

Let me know if this seems to be your problem and we'll discuss further.

THE LONG ISLAND GARDENER