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Prunus spinosa

Common names: Blackthorn, sloe, wild plum, wishing thorn or mother of the wood. 

Irish name: Draighean 

Latin name: Prunus spinosa 

Family: Rosaceae 

Origin: Native 

Tree type: Deciduous broadleaf tree

How it Looks

Shape, Bark, Twigs

The blackthorn is densely branched with twigs forming straight side shoots that develop into thorns. Mature trees can grow to a height of 7m. The blackthorn's common name comes from its dark bark, which ranges from brown to nearly black. The outer bark is extremely thin, and just under its surface, it is a bright orange colour. When young, its bark is generally quite smooth but becomes rough and spotted with brown-orange ‘breathing pores’ (lenticels) with age.  

Buds

Blackthorns have tiny alternate buds between 1 and 2 mm. They are red/brown and hairy, usually having auxiliary buds on either side.  

Thorns

The thorns are about double the length of those of the Hawthorn. Most thorns of the blackthorn have buds on them, whereas the hawthorn may have a side shoot with buds that ends with a thorn, but the thorn itself does not have buds. 

Leaves

The leaves of the blackthorn open in April/ May after the flowers. The leaves alternate up the stem, are slender and oval, and grow between 2 and 4 cm. They have toothed edges and hair on the veins beneath.  

Flowers

The blackthorn tree is an early bloomer, typically flowering in February or March, depending on the winter conditions. Its creamy white flowers are a distinctive feature, appearing on hedgerows long before most other plants and before the tree's own leaves emerge. Blackthorn is a hermaphrodite, meaning it has both male and female reproductive parts in a single flower. These white flowers have five sepals and five petals, and the anthers are yellow. 

Fruits

Following pollination by insects, the flowers transform into blue-black fruits, each approximately 1cm in diameter. These fruits, known as sloes, are exceedingly bitter and resemble small plums. They are ripe and ready for picking in October and are often covered with a white powdery yeast fungus. While initially green when unripe, they turn black as they mature.

Similar Species

Hawthorn (Crataegus monogyna). The flowers of blackthorn appear before the leaves, and the spines have buds along their length, while the hawthorn flowers emerge from the same point as the buds. 

Where to Find It

Blackthorn is a common sight in rural Ireland, where it frequently adorns hedges, scrubland, woodland edges, and rocky or scree slopes. Additionally, blackthorn can take root in shingle areas, where it grows flat to the ground, known as prostrate form. The plant prefers moist, well-drained soil and flourishes in full sunlight.  

It is also native to Europe and western Asia but has been introduced to New Zealand and eastern North America, where it is now well established.  

Cultural Importance

History | Myth | Literature

History 

The blackthorn is probably best known for its fruit, the sloe berry. Evidence from various archaeological excavations throughout Europe demonstrates that people were consuming sloes as early as the Mesolithic period (between 10,000 and 7000 years ago). References to sloe fruit in early Medieval Irish texts suggest that this practice continued in Ireland into the 9th century AD. Likewise, sloe berry seeds recovered from excavations at Fishamble Street and Little Mary Street in Dublin indicate that the sloe was consumed in large quantities during the later Medieval period. 

With regard to blackthorn wood, charcoal remains discovered during archaeological excavations at Glebe, County Kilkenny in 2006 suggest that blackthorn was widely used for fuel during the Bronze Age (c. 2500-800 BC). Mention of the wood also features in early Irish texts revealing that on account of its thorniness, blackthorn was valued as a stock-proof species during the 5-9th centuries AD – the early Medieval equivalent of today’s barbed wire! Deemed important for this purpose and for its fruit, blackthorn was included in the early Medieval tree lists as one of the ‘Lower Divisions’ of the wood. This meant that if a person unlawfully damaged or destroyed a blackthorn they would have to pay a substantial fine as compensation.  

Blackthorn was of such significance during the Medieval period that it was included in the early Irish Ogham alphabet, where it gives its name to the Ogham character that represents the letter ‘SS’ or ‘Z’: 

In later periods, blackthorn wood was used to make walking canes and shillelaghs - a type of walking stick or cudgel traditional to Ireland, while its bark, flowers, and fruit were used in tonics and syrups for blood cleansing, digestion and rheumatism relief. The fruit was also used in preserves, wines and to flavour gin and poteen. 

According to an early Irish glossary, the Irish name for blackthorn, draighean, comes from the words Trog-aon, which translate as ‘wretched one’ - a negative reference to its thorniness. This is perhaps where some of its darker associations stem from. This name is frequently found in Irish placenames. Indeed, there are no less than six places called Drinagh (in Counties Clare, Cork, Galway, Laois, Offaly and Wexford) or the Irish Draighneach, which translates as ‘place of blackthorns’. There is also Dreenagh, in Co. Kerry. 

 

Myth, Legend and Folklore 

Traditionally, the blackthorn is variously associated with the qualities of protection, misfortune and beauty.  

In Ireland, a blackthorn stick was believed to provide protection against fairies, evil spirits and the devil. However, it was also believed that the tree was sacred to supernatural beings called ‘lunantishees’ and that to cut a blackthorn on the 11th of May or 11th of November would bring bad luck. In a similar connection, it is often associated with witches and ‘hostile’ or warlike women. In the Irish myths, blackthorn is connected with war, and in one story, the seven sons of Queen Meadhbh ward of their enemy with a blackthorn fence. In contrast, in other contexts the blackthorn was a symbol of female beauty. 

 

Literature 

Blackthorn often features in early Irish poetry in a negative light due to its thorns and associates with misfortune, as in the poem Sweeney’s Lay. Similarly, Iubhdán’s poem, the king of the fairies warns Fergus mac Léide, King of Ulster, that the blackthorn should not be burnt. However, in the poem, Green Rain, the Romantic poet Mary Webb describes the beauty of the blackthorn flowers. 

Value to Wildlife

Blackthorn plays a vital role in supporting various species. In spring, its early flowering provides a crucial source of nectar and pollen for pollinating insects, aiding in their survival and the pollination of other plants. Furthermore, blackthorn's foliage serves as a food source for the caterpillars of numerous moth species, including the lackey, clouded silver, brimstone, magpie, swallow-tailed, and yellow-tailed moths, as well as being a favourite of the brown hairstreak butterfly. 

Birds find blackthorn especially hospitable, using its dense, thorny thickets as nesting sites. Species like the blackbird, song thrush, dunnock, finches and common whitethroat are among the many that take advantage of this natural shelter. Birds further benefit from the blackthorn's ecological significance by consuming caterpillars and insects that inhabit the leaves, as well as feasting on the sloes that develop in autumn. 

Sloes, the blackthorn's small, sour fruit, serves as a valuable food source for birds. The unique dusting of yeast bloom on the fruit's surface is an evolved strategy to enhance UV light reflection, making the fruits highly visible to birds with UV vision. This prompts birds, particularly migrants like redwings and fieldfares, to feed on the sloes and disperse the seeds across various locations, facilitating seed distribution and growth. 

Threats

The species is not known to suffer any significant threat from pests or disease. To learn more about threats to Irish trees, visit ‘Threats to Trees’  

Uses

Blackthorn's tough and hardwearing wood is ideal for making walking sticks and the iconic Irish shillelaghs. Blackthorn wood is also used for decorative crafts and souvenirs. The wood's light-yellow hue with brown heartwood adds to its versatility and enduring appeal. The thorny and fast-growing blackthorn is still a popular choice for cattle farmers, making their hedgerows stockproof. Likewise, sloes are still used to make wines, preserves, and sloe gin.  

 

References

Irish Tree Explorers Network

Líonra Taiscéalaí Crainn na hÉireann

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