We have two dogwood trees in our yard that look like they are dying. The house was built in the 1960s, and we just bought it about 5 years ago, so I don't know when the trees were planted. But I seem to remember reading that dogwoods only last around 15 years? I know that trees must have different life spans--like the sequorias (sp?)in the Western U.S. that are really old. What can anybody tell me about this topic? Thanks!