Think its safe to begin fertilizing trees and shrubs in Tucson yet? Doesn't appear there will be anymore frosts in the next 10 days. (Mid-30's next weekend, but not freezing.)?
I tend to not fertilize until after the danger of frost is past. My thinking is that the fertilizer will get the plant growing more actively and push out new, tender growth. If we have another freeze then all the new growth will get nipped off. Might make a difference in what you're fertilizing and whether or not it's frost tender.