One species each day (from my backyard)

It was a nice and sunny enough weekend and one or two confused flowers woke up too early on one of the two plum trees. Here's one of them. Again I thought it would be an easy one to identify, but again I was mistaken, with Wikipedia telling me that there are between 19 and 40 different plum species, depending on which botanist you ask. However, I assume it's nothing fancy, so I'll call it a Prunus domestica.