I have several ninebark in my yard, all of them grow in sunny well watered flowerbeds. The plants seem healthy and grow well each year. I do prune them down to about four feet high each summer at least once or twice. Since they do grow quickly. My question has to do with the ninebark's change in color over the years. One ninebark was a deep plum color with no green showing for the first three years and then over the next few years the leaves gradually changed to have more green in them. Now the leaves are more green than plum. Another ninebark has always had a nice blend of green and deep plum red leaves, but this year the stems and leaves in one area of the plant are all a gray white color. Best I can tell the leaves look healthy. These gray white leaves didn't really show until I pruned the bush down to its usual four foot height. What causes the change in color and is there anything I can do to prevent it?
Lane County Oregon
From reading, many ninebark change color during the year.
The intense weather in 2014, 2015 and 2016 also affects the color of foliage and bark, mainly due to water stress.
Plus pruning brings on new, vigorous growth.
Okay. The color change makes sense. But what about the leaves and stems that are a grayish white color. Some additional research makes me think it might be powdery mildew. Can I just remove the stems and leaves that have the white color or does it need more aggresive treatment? If so what kind of treatment and how do I keep it from happening again?
Powdery mildew is a white fungus that grows on many plants and is very common.
Almost any good garden fungicide would control the powdery mildew, even baking soda in water.
To be sure, take a sample to the OSU Extension Lane Co Master Gardeners, 996 Jefferson, corner of Jefferson and 10th for a closer look.
As for happening again, powdery mildew happens on many plants int he Lane County area each year - due to the summer and fall weather.
Sorry, I notice you were from Minnesota and not Oregon - look for a local Extension office in your area and have them take a close look at the white area on the bark.
I am not sure why you think I am from Minnesota, I live in Oregon, in Eugene.
In the AAE paperwork, there was reference to Minnesota Yard & Garden Group AND Lane County.