June 14, 2012
My Damson tree is now 3 years old. It flowers well and the tree looks fine each year; however, no fruit ever appears. Following the flowering, the tree looks a bit sad and the leaves curl in places but no sign of pests. My other plum trees in the garden (different types) do well for fruit each year.
June 20, 2012
You did not put where you live, so I can't be sure of this, but it is possible that the tree may not be getting enough chilling over the winter. How much chilling varies from variety to variety, so the other plums in the yard may be getting enough chilling for their variety but the damson does not. Without enough chilling the flowers cannot produce fruit.