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Blackthorn

Prunus spinosa

The Blackthorn is a widespread deciduous shrub of medium size with dense, thorny branches. With its well-developed root system, it propagates quickly by way of stump suckers and tillers, often forming dense, nearly impenetrable thickets which are ideal shelters for birds. In the Donau-Auen National Park, the Blackthorn's impressive masses of white flowers appearing before the leaves make it one of the most conspicuous settlers of its hardwood riparian forests and slope forests.

Description

The Blackthorn is a deciduous, slow-growing, squarose (scaly), densely-branched shrub which reaches a maximum height of 6m. Its small branches end in numerous short thorny shoots which stand at nearly right angles to the stem. A shallow-rooted plant, the Blackthorn develops extensive root growth with numerous suckers ("creeping root pioneers"). Its twigs are angular to round, reddish-brown in colour; older branches and trunks have a rust-coloured to blackish-brown bark which ultimately tears off in strips. The small buds are berry-shaped to egg-shaped; leaf buds are often flanked by two flower buds. Leaves are alternating and often arranged in bunches; leaf shape is broadly oval to elliptical, 5cm long and 2.5cm wide at most; colouring dark green on top and hairless, pale green on the underside. Leaf margin is finely toothed or notched. Prior to foliation, the Blackthorn unfolds its attractive, snow-white blossoms, usually between March and May. The flowers – mostly single, sometimes paired – are arranged on the short shoots in little bushels and emit a powerful scent. The flowering shrub is an important first bee pasture in spring. The round, dark blue sloes are usually 1-1.5cm large, are found on all sides, and ripen in September/October, remaining on the shrub for a long period. The flesh of the fruit, which is rich in vitamin C, tastes tart; it becomes sweeter after exposure to frost. The hard, fine-grained timber displays reddish sapwood and a brown-black core. It is well-suited for polishing and is much sought after by turners.

Distribution

The Blackthorn is native to nearly all of Europe except for the extreme north and in Iceland. In Austria, the shrub is found in all provinces. In the Donau-Auen National Park, it is most often occurring in the hardwood riparian forests and slope forests as well as in sunny areas at the edge of forests. In North America, the species is naturalized and may be found in south-eastern Canada and New England in the US.

Endangerment and Conservation Status
Not vulnerable in Austria or in Europe.

Ecological Characteristics
The Blackthorn favours nutrient-rich, alkaline soils rich in humus, or arid and well aerated soils in sunny locations. It grows in broadleaf forests which are not too dense; on woodland margins; on dry slopes; in hedges and bushes as well as the more arid parts of wetlands habitats. A highly adaptable plant with regard to soil moisture, the Blackthorn may be found from the lowest elevations up to heights of around 1400m.

Special Characteristics
Rich in vitamin C, the fruit of the Blackthorn is used to make sauces, juices, compotes and conserves. It is also used to make schnapps and other liqueurs. As far back as the Neolithic era, the Blackthorn has been cultivated as a food crop. In antiquity its healing properties were much admired, and today various parts of the plant – flower buds, leaves, fruit and bark – are utilized in naturopathy; substances are believed to have diuretic, laxative and blood purifying properties. In the Middle Ages, so-called "rust thorn ink" was made from its bark: light-fast and waterproof, it was commonly used by monks. The Blackthorn's highly-developed root system and its ability to propagate quickly by way of stump suckers and tillers has made the shrub useful for planting on slopes to discourage soil erosion. Thick Blackthorn hedges are also valuable hideaway places for birds.