Sloe, or blackthorn (Prunus spinosa), is a small, dark purple fruit tree native to Europe and western Asia. Culinary use of sloe fruit is limited by its natural astringency and sourness, but it is traditionally used as a flavoring agent for alcoholic beverages. It is thought to be a genetic parent of the modern plum.
The best-known product is sloe gin, a British liqueur made by macerating the fruits in gin with added sugar, a practice documented since at least the 18th century.
In northern Spain, sloe berries are used to produce patxaran, an anise-flavored liqueur with origins in the Basque region, dating back to the Middle Ages.
Sloes are also occasionally employed in preserves, jellies, and as a flavoring in other regional spirits and desserts, although their culinary uses outside of beverage preparation are relatively limited due to their tartness.
