Can anyone shed any light on a little mystery? At the bottom of my garden are two large plum trees. They never have much fruit, but what they do have tastes great. I already know that they have canker (lots of gooey sap leaking from the branches), but this year I have noticed that although there are some small plums beggining to form, most of the branches seem to be growing pods (very much like a pea pod) which contain what look like peas! Does anyone know what this might be?