These are from a tree in our back yard. This is the 15th year we've lived here, and I can't remember it bearing fruit before. We had no idea what these were. We sent a picture of the tree to my wife's sister, who claims to know about such things, and she said not to touch them, because they looked poisonous! Then a friend who has lived in Boulder all her life came over, took one look at them, and said they're wild plums, and, over my wife's protestations, ate one. They are quite sour (sort of the plum equivalent of crab apples), but cook really well with sugar (you have to take the stones out, which takes a long time). They are especially good in plum brandy, plum gin, plum vodka, plum... you get the idea. This is a 23 shot focus stack.