In article , kenty ;-)
writes
Can anyone give any advise on when & how to crop damson.This is my first
year in my house so I haven't cropped before.The fruits at the moment are
starting to turn purple.

Later, once they are completely purple.

When I lived in kent we used to pick damsons from the hedgerows to make
jam - we didn't move into that house till September.
--
Kay
"Do not insult the crocodile until you have crossed the river"