A Few Observations on Powdery Mildew
Tofino, British Columbia
I was originally referred to as the "Magic Johnson of the rhodo world," mainly because I was one of the first to admit "I've got it."
Ever since the day Warren Berg and a couple of others pointed out I had a powdery mildew problem I've tried to find a solution to the cause. I have looked at gardens along the western side of North America, in Tasmania, Australia, New Zealand, England and Scotland. I have found that all gardens with a western exposure are affected. The closer the gardens to open water the worse they are. Fellow gardeners used to say "it's that wet climate of yours." So, tell me why Victoria city has one of the worst cases with only 27 inches of rain per year compared to our 12½ feet?
The answer, I have discovered, is "wind," and a westerly wind at that. Victoria is known as a windy city and principally westerly winds.
I can show you, here on the west coast, where Rhododendron 'Virginia Richards' looks great in an easterly wind exposure. In recent years, it's difficult to find this plant alive in Victoria.
I have stood in a mature Victoria plantation of this variety and they are all dead or beyond hope. I have tried anti fungus sprays of many types, but find the best answer is to move the infected plant to the east, sheltered from the west in your garden, or chop it down. You would be "at it" forever trying to spray them and no gardener is here forever.
I have placed my affected varieties in neighbours' yards, district parks and on the east side of my hill - all with this "theory" in mind. It takes time to prove a point and I hope I'll soon be back to show you the proof.