AppearanceBlackthorn is 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 to 4.5 cm long and 1.2 to 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 to 12 mm in diameter, black with a pale purple-blue waxy bloom, ripening in autumn, and harvested — traditionally, at least in the UK, in October or November after the first frosts. Sloes are thin-fleshed, with a very strongly astringent flavour when fresh.
It is frequently confused with the related cherry plum, particularly in early spring when the latter starts flowering somewhat earlier than. They can be distinguished by flower colour, creamy white in pure white in. They can also be distinguished in winter by the more shrubby habit with stiffer, wider-angled branches of in summer by the relatively narrower leaves of, more than twice as long as broad. In autumn it can be identified by the colour of the fruit skin — purplish-black and yellow or red.
Blackthorn is a winter tree and is very hardy, it has black bark and is armed with vicious thorns and can be found growing in dense thickets. Its wood and its thorns are used for offensive magic like thundersticks or piercing effigies. The plant itself has come to represent fate or outside influences that must be followed.