We have a plum tree that is, at the moment, covered in fruit. Last year, when we were still new to the neighborhood and just getting over the pleasant shock of realizing that the ugly bundle of sticks protruding from our concrete postage stamp backyard was actually a gorgeous fruit tree, we spent quite a long time wondering why only a small amount of the fruit was ripening. Then one day my mom polished up one of the "unripe" plums and discovered that apparently what we have is a yellow plum tree with a few regular plum branches grafted in just to psych us out.
The plums of both colors are great, but you really only want to eat so many at a time (unless you are 18 months old, in which case you want to eat as many as you can possibly get your hands on, and no, you don't want any help with that). Last year we were out of town right when they were at their best, so we ended up with loads of wasted fruit. This year we vowed to make better use of the free sweet yummy goodness in some way or another. The 18 month old is doing his part, and I decided to take a swing at doing mine this morning when I realized that we had no jam in the house.
Since I took the super lazy speedy route, the result was quite goopy, but it tasted wonderful.