Here's a self portrait, head hard as rock but full of holes. One of the hazards of being an amateur are the holes. More systematic and professionally guided courses of learning don't leave as many holes. But isn't it fun filling them in? Yesterday's discovery was growing degree days (GDD). Wiki says this is a heuristic tool in phenology. Fortunately they go on to say it is a calculation used by growers to figure out how long it may take to produce flowers or fruit. That item includes imposing mathematical formulas. Obviously, I have much to learn in general, and about growing degree days in particular. How can it take 1500 growing degree days to produce oats? Much to learn here!