The stiff purple discoloration that hit our courtyard dogwood has now spread to my J. hydrangea and v. creeper. They are very stiff and then fall off. Last year the tree defoliated and then didn't bloom in the spring. Someone suggested heat stress. I'm from the north so I'm unfamiliar with the symptoms. It's no hotter than usual -- 85-95. If it is heat stress, any suggestions other than shading them?

FYI: The underside of the leaf is a lighter green without the purple-brown.

Thanks! http://forums.gardenweb.com/forums/pests/msg0720315222899.jpg

When similiar symptoms occur across types of unrelated plants, the problem is usually environmental and not an infectious disease. There are two possibilities for the purpling. One is heat stress and there is not much one can do but try to give the plants some light shade. The other is a phosphorus deficiency and occurs more on sandy to silty soils. You can have the soil tested for phosphorus and if too low - treataccording to the soil labs recommendations. Sometimes phosphorus is not available even though there is adequate amounts in the soil. Sometimes other nutrients are in excess will react with the phosphorus and thus it is no longer available to the plants.