Ran into this in the front ranges in Alberta. I'd not noticed red willows before this. The shot is at an elevation of 5400 feet. Just high enough that poplar are absent. The ground cover on valley floors is overwhelmingly a mix of autumn willow and dwarf birch. The willow in this area is just starting to fluff. Some plants still have intact seed capsules (correct term?) Others are masses of seed hairs getting ready to set sail. I snapped this shot because it had an unusual concentration of red leaves, but red leaves appeared in various willows in this area. As you can see from the large picture, predominantly end leaves are affected. This fits with many other fall colour shifts, that leaves with a clear view of the sky are chilled more. How unusual is this? It was too common to be a branch sport. So my guess right now is that it has to be just the right combinaton of micro climate, or a virus. Thoughts?