Blackthorn

Prunus spinosa

Sloes are the blackish-blue fruits, measuring 1 to 1.5 centimetres across, that grow on Blackthorn. They are drupes, not berries. A drupe has a thin outer skin, a fleshy or fibrous middle, and a hard, stone enclosing a single seed. Plums, cherries, peaches, nectarines, and apricots are all types of drupe. Sloes are extremely bitter so are not usually eaten raw. However, they are used to flavour gin and to make jams, jellies, syrups, and preserves.