Greenup is that brief period of time, sometime in May, that all the trees turn green (commonly called spring in the lower 48). This time varies, usually starting in early May in south Alaska and getting a little later as you move north. Literally overnight, we go from the brown world of mud, limb, and dirty snow bank, post breakup, to the lush yellow-green of a newly reawakened boreal forest. In Fairbanks, this can happen in a matter of days, you can see changes in the hillside colors from morning to night. Recent years have seen a change in schedule, with greenup appearing to come earlier and earlier each year. (You guess the reason, I’m sure it isn’t human caused.)