Prunus spinosa, commonly called Blackthorn, or Sloe, is native to native to Western Asia: Iran [n.w.]; Turkey; Caucasus: Armenia; Azerbaijan; Georgia; Russian Federation - Ciscaucasia, Dagestan.

Europe:
Northern Europe: Denmark; Finland; Ireland; Norway; Sweden; United Kingdom; middle Europe: Austria; Belgium; Czechoslovakia; Germany; Hungary; Netherlands; Poland; Switzerland; eastern Europe: Belarus; Estonia; Latvia; Lithuania; Moldova; Russian Federation: Ukraine; southeastern Europe: Albania; Bulgaria; Former Yugoslavia; Greece; Italy [incl. Sardinia, Sicily]; Romania
Southwestern Europe: France [incl. Corsica]; Portugal; Spain [incl. Baleares]. [1]

Sloe is also widely naturalized in the Pacific Northwest and British Columbia, the northeastern U.S., the states of Missouri, Tennessee, and Illinois. [1]

A deciduous large shrub or small tree growing to 5 m tall, with blackish bark and dense, stiff, spiny branches. The leaves are oval, 2 - 4.5 cm long and 1.2 - 2 cm broad, with a serrated margin. The flowers are 1.5 cm diameter, with five slightly creamy-white petals; they are produced shortly before the leaves in early spring, and are hermaphroditic and insect-pollinated. The fruit, called a "sloe" is a drupe 10 - 12 mm diameter, black with a pale purple-blue waxy bloom, ripening in autumn, and harvested in October or November - usually after the first frosts. They are thin-fleshed, with a very strongly astringent flavor when fresh. [3]

Sloe foliage, flowers and pollen are eaten by the larvae of Lepidoptera including Emperor Moth, Common Emerald, November Moth, Pale November Moth, Mottled Pug, Green Pug, Brimstone Moth, Feathered Thorn, Brown-tail, Yellow-tail, Short-cloaked Moth, Lesser Yellow Underwing, Lesser Broad-bordered Yellow Underwing, Double Square-spot and the Black and Brown Hairstreaks, as well as blister and other beetles.

The fruit is similar to a small damson or plum, suitable for preserves, but rather tart and astringent for eating, unless deeply frozen, as is practiced in eastern Europe. In rural Britain so-called sloe gin is made from them, though this is not a true gin but an infusion of vodka, gin, or neutral spirits with the fruit to produce a liqueur. In Navarre, Spain, a popular liqueur called patxaran is made with sloes. Sloes can also be made into jam and, if preserved in vinegar, are similar in taste to Japanese umeboshi.

Extensively planted for hedging and for cover for game birds. The small thorns of the plant are relatively common causes of minor wounds in livestock, and these wounds often fester until the thorn is expelled or removed.

Straight blackthorn stems have traditionally been made into a walking stick or club (known in Ireland as a shillelagh).  The wood would be smeared with butter and placed up a chimney to cure, giving the Shillelagh its typical black shiny appearance. Shillelaghs may be hollowed at the heavy "hitting" end and filled with molten lead to increase the weight beyond the typical two pounds; this sort of Shillelagh is known as a 'loaded stick'.

Shlomo Yitzhaki, a Talmudist and Tanakh commentator of the High Middle Ages, writes that the sap (or gum) of the Prunus spinosa (or what he refers to as the Prunellier) was used as an ingredient in the making of some inks used for manuscripts.

A "sloe-thorn worm" used as fishing bait is mentioned in the 15th century work, The Treatyse of Fishing with an Angle, by Juliana Berners. The expression "sloe-eyed" for a person with dark eyes comes from the fruit, and is first attested in A.J.Wilson's 1867 novel Vashti. [3]