Sloes are, of course, the fruits of the blackthorn (Prunus spinosa) and people like to collect them to make sloe gin! One has to be careful though as the blackthorn has fearsome spines and for every sloe you pick you are likely to feel the sharp end of a thorn. The spinosa of its scientific name is a reflection of the spines on this plant.
The blackthorn is common across Dorset and is most obvious in spring when the white blossoms are in full flower. In autumn they are far less conspicuous as the dark fruits are much harder to spot in the hedgerow. They are not small fruits and are dark purple, almost black, when fully ripe.
The sloe is also known as the wild damson but sloes are rather sour and cannot really be eaten raw. In addition to sloe gin you can make sloe jelly, a kind of smooth jam. Home winemakers use them to make spurious port wine, some mix the juice with port to give it a more bitter taste (a waste of good port if you ask me!). If you want to make sloe gin there are several recipes on the Internet.