I live in Chicago, and have 3 trees that are dying this year. I have asked around, and except for last years drought, no-one has any ideas. We have several trees about the same age that are doing great, including a dwarf peach, river birch, blue spruce, dogwood etc. The problem is with the Nishiki willow, the corkscrew willow, and a dwarf Northstar cherry. Both willows have severe die back, and the cherry started to fruit and then shriveled and has almost completely died. All receive identical care, i.e. fertilizer, water, etc. Any ideas?