Home grown plum trees produce very sweet fruit. They will taste far superior to any store bought plum. This is because plums do not keep well and have to be eaten fast. When store bought plums are harvested they are unripened and cannot continue to develop sugar. So store bought plums will be less sweet than home grown.
Most varieties of plum are ready for harvesting in August. Once they are harvested they should be eaten quickly.
Most plums require cross-pollination (2 different, yet compatible varieties). Click here for Pollination Chart.