Blackthorn (sloe)
Prunus spinosa
Botanical family: Rosaceae
Prunus spinosa, a wild shrub common in Europe's hedges and edges, covers itself with white flowers from the end of winter, well before the leaves appear. Its fruits, the sloes, harsh and astringent when raw, are traditionally harvested after the first frosts for infusion, sloe liqueur, or jam.
Sun to partial shade
Any soil, even poor or chalky
Low once established, very drought-resistant
Very hardy (withstands -25 °C)
Overwinters in your zone
Role in permaculture
A thorny shrub with vigorous suckering, blackthorn forms dense, impenetrable hedges that protect the garden and shelter abundant wildlife (nesting, insect overwintering). Its early white flowering, from March before the leaves, offers one of the first sources of nectar and pollen of the year for bees coming out of overwintering.
Insects attracted or useful
Documented synergies
Relationships backed by a named source, with their real scope. A synergy without a named reference has no place here, no “it is said that…”.
A very early flowering, often before the leaves (February–April), offering pollen and nectar when few plants are in bloom. The blackthorn depends heavily on insects to fruit: under bagging, its fruit production drops markedly. The relationship is therefore mutual, but the benefit to the pollinators themselves stays moderate and variable with the floral competition of the moment.
scientific study
- · Jacobs J.H. et al. (2009), Annals of Botany 104(7):1397-1404, DOI 10.1093/aob/mcp236
An important point near an orchard: the wild blackthorn is a natural, symptomless reservoir of a phytoplasma that causes European stone fruit yellows (chlorotic leaf roll of stone fruit, plum, apricot, peach), and it hosts its insect vector, the psyllid. A large German study found the infection in 14% of 437 blackthorns across 104 sites, even far from any orchard. It therefore keeps the pathogen in the landscape, a reason for caution about planting it near sensitive fruit trees.
scientific study
- · Jarausch B. et al. (2019), European Journal of Plant Pathology 154:463-476, DOI 10.1007/s10658-019-01669-3
The blackthorn is the main host plant of the brown hairstreak, a butterfly whose caterpillar feeds on its young leaves in spring; its thorny hedge also shelters other lepidoptera. To be clearly distinguished: it's a BIODIVERSITY service (it supports a heritage butterfly), not a beneficial predator of pests, don't confuse the two.
scientific study
- · de Vries H.H. et al. (2011), Journal of Insect Conservation 15:311-319, DOI 10.1007/s10841-010-9355-6
Seasons & availability
Very early white blossom in March and April, before the leaves; sloes, harsh and astringent raw, are picked after the first frosts, from October to December, for liqueur, jam or jelly. Increased mainly by suckers, plants or cuttings rather than from seed.
Available: October, November, December.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Plants For A Future, « Prunus spinosa » (pfaf.org/user/Plant.aspx?LatinName=Prunus+spinosa)
- Woodland Trust, « Blackthorn (Prunus spinosa) » (woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/a-z-of-british-trees/blackthorn)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Never eat the kernels contained in the stones: as in the other Prunus (apricot, cherry), they contain amygdalin, a cyanogenic compound. The pulp, however, does not pose this problem. Raw and unripe, the sloe is extremely astringent and can cause digestive discomfort: it's harvested after the frosts and processed (cooking, maceration). In case of a persistent disorder or an ongoing treatment, seek the advice of a doctor or pharmacist.
Family behaviour: Rosaceae
In general, Rosaceae are traditionally paired with garlic (reputed antifungal, an in-vitro effect against Venturia inaequalis but little demonstrated in the field), tansy and comfrey. This is the fruit family (strawberry, raspberry, apple, pear, cherry, plum, peach). Tansy is the emblematic companion of the apple tree guild.
Understanding families means learning one rule per family rather than every pairing one by one. Learn more →
Species & varieties
The best-known species and varieties in France.
Common varieties
Before you forage
This plant is often gathered from the wild. Only pick what is abundant, never a protected species, and never uproot a whole plant (roots) without the landowner's permission. Rules vary by country and region, check locally.
Key takeaways
- • Prefers sun to partial shade exposure.
- • Ideal soil: any soil, even poor or chalky.