Old Green Gage is the definitive "gage", and often considered the best flavoured of any plum variety. Compared to the attractive colouring of most plums, the appearance of Old Green Gage fruit is fairly plain - the plums are quite small and a dull green colour, turning slightly yellow when ripe. However this is one that you grow for flavour - for eating fresh it is exceptional.
Old Green Gage has a fascinating history. The gages are usually included within the European plum species Prunus domestica, but are nevertheless a distinct sub-group, being smaller and more spherical, and green or yellow in colour. They have been cultivated in France since the Middle Ages having been introduced from Italy. In France the many different varieties of green-skinned gages are known collectively as "Reine Claude" in honour of Queen Claude, the wife of Francis I who ruled France from 1515 to 1547. Old Green Gage is believed to be the same variety as the French Grosse Reine Claude.
It is generally thought that Old Green Gage was introduced to England from France in the 18th century by Sir William Gage, who lived at Bury St. Edmunds and obtained a tree from his brother who was a priest living in Paris. As a result of his promotion of this new variety all green plums tend to be known as "Gages" in the UK. However, whilst Sir William is undoubtedly responsible for the English name, and the Old Green Gage in particular, there is some evidence that his was in fact a re-introduction of a variety already widely grown in England known as Verdoch, which may have come to England from Italy in the Middle Ages.
Green-skinned gages were subsequently introduced to the USA in the late 18th century where they are also known as Green Gages.