I have waited 7 years to grown damsons in my garden.
Damson is a small member of plum family, in the photo the fruit are about 2cm long. Today it is very unlikely you will see damson for sale in shops, but in rural areas, it is sometimes possible to buy at the farm gate (usually from a tree in the farm house garden; damson orchards have almost totally disappeared from the English countryside - at their height, the UK commercial demand for damsons was only about 5 tonnes, most of this was used to make jam). Many damson trees grow in hedgetows in the English west Midlands. It is a fruit that is always cooked as it has a strong taste, not exactly bitter, not astringent, but very intense and slightly acidic. When cooked, the deep purple colour comes out from the skin making the cooked puree of fruit deep purple colour.
Why 7 years ? I ordered a 2yr old tree described in the catalogue as "prolific bearer of tasty fruit" I planted it, three years later it produced its first fruit . . . but these were small round plums and when cooked turned into a brown stew with bits of bleached skin. They had hardly any flavour. I searched again and found an "old Englsh" variety of damson with good internet reviews, I bought one and removed the previous tree.
My new tree took 3 years to produce fruit, but all fell off before they were ripe. This might have been because the tree was still too young to produce fruit to maturity. However, this year it has plenty of fruit and in a week or two I will harvest them and stew the into a delicious deep purple puree, add some sugar and put most in the freezer.
I enjoy having cooked damsons with my breakfast porridge or for dessert as a "crumble" served hot with thick creamy English custard.