I have 2 plum trees in my yard. A SD hybrid tree and a native MN tree. The SD one is a self fertilizing and I have read and heard that the native MN is also self fertilizing. The SD has not born fruit for the 8 years I've had it. The MN has produced fruit the last 2 years.. Last year it produced a solid small fruit that then became a larger hollow fruit. There were small brown spots on them before they started shriveling up. I thought it had been because i didn't water them well enough last year, but it happened again this year. The SD is producing some plums and are at a small stage at this point.and I am waiting to see if they shrivel up. There was a small hole and brown spot on one of the SD plums