lack of leaves on plum tree
My plum tree only has leaves on the lower branches. The upper branches are completely bare.
Plum trees are susceptible to a number of diseases. https://www.gardeningknowhow.com/edible/fruits/plum/plum-tree-diseases.htm
You should probably check with a master gardener to make sure your problem is not coming from disease or bugs. This link will help you: http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/
If there's no disease or bug, it's time for some pruning: https://www.gardeningknowhow.com/edible/fruits/plum/plum-tree-pruning.htm