Blackthorn Plant Care

Blackthorn (Prunus spinosa) belongs to the Rosaceae family within the Prunus genus. Blackthorn is native to Europe and West Asia, and has been naturalized in parts of North America. Blackthorn is also known as Sloe, Sloe bush, Bullace.

Blackthorn displays an upright, spreading tree growth habit, reaching up to 20 ft tall with a spread of approximately 15 ft. Blackthorn produces showy clusters of white or pink blossoms.

Leaf size: approximately 4 inches.

Water a young or newly planted Blackthorn every 7–14 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established trees mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Blackthorn thrives in full sun to partial shade.

Prunus spinosa tolerates temperatures of 10–90°F. Blackthorn prefers humidity levels of 40–70%.

Well-draining loamy soil with good organic content. Good drainage is essential for Blackthorn to prevent waterlogging, which leads to root rot and fungal issues.

Feed Blackthorn every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established trees in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun to partial shade and well-draining loamy soil with good organic content. Avoid low spots where water collects after rain.

Blackthorn is suited to USDA Zone 4a – 8b.

Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.

Blackthorn can spread to about 15 ft (4.6 m) and reach about 20 ft (6 m) tall. Space plants about 15 ft (4.6 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the tree spacing calculator.

Prune Blackthorn while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the tree in one year.

Blackthorn is hardy down to USDA zone 4a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown trees need extra protection: roots in a pot freeze much more easily than roots in the ground.

Blackthorn can be propagated through softwood cuttings, hardwood cuttings, grafting. Similar propagation techniques also apply to apricot tree plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Blackthorn is susceptible to aphids, scale insects, caterpillars. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Blackthorn grows outdoors in USDA Zone 4a – 8b. It survives winters down to planting zone 4a. Blackthorn is native to Europe and West Asia, and has been naturalized in parts of North America.