Images: ©Jouko Lehmuskallio
Blackthorn
Prunus spinosa
- Name also: Sloe
- Family: Rose Family -Rosaceae
- Growing form and height: Shrub. 1–4 m (3–13 ft.).
- Flower: Regular (actinomorphic), strong-smelling, ca. 10 mm (0.4 in.) across. Calyx-lobes 5, elliptic, with membranous margins, hairless. Petals 5, white. Stamens almost 20. One carpel. Flowers solitary or in pairs, on thorn-tipped branches or short shoots.
- Leaves: Alternate on the annual shoot. Fairly small, short-stalked, with fine-toothed margins, greyish-green beneath, veins hairy.
- Fruit: A globose, blackish drupe with a bluish bloom and a large seed.
- Habitat: Rocky places, waysides, rock outcrops, dry meadows, coppices. Often on calcareous soils.
- Flowering time: May–June.
The blackthorn is a densely branched, usually 2–3 m (6–10 ft.) tall shrub with long and sharp thorns. By means of root suckers it often forms impenetrable thickets which are excellent nesting places for birds and small mammals. The blackthorn flowers before coming into leaf in spring. The flowering is quick but showy. The flowers are insect-, especially beetle-pollinated.
The plum-like fruit ripen late. They are sour at first but become sweeter after the first frosts. Then they can be used e.g. for making squash or liqueur. Because the fruit are rich in tannic acids they have a strong contractive effect on mucous membranes and, hence, have been used as medicine.
The blackthorn, also known as sloe, belongs the genus of cherries and plums (Prunus). The genus is large comprising 200–400 species, depending on the definitions. In Finland, the blackthorn occurs only in the Åland Islands and the south-western archipelago. It doesn’t thrive inland, but shoot parts above the snow-line freeze.
