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Prunus spinosa
Caution🐾Schlehdorn · (Prunus spinosa)
Rose family (Rosaceae)
Description
With its thorny branches and dense clusters of white blossom, blackthorn (Rosaceae) is a striking feature of the hedgerow landscape as early as late winter. Before the first frost, the deep-blue fruits taste intensely astringent; cold or freezing lowers their tannin content from around 10 g/l to less than half, making them palatable raw. An infusion of the dried fruit is recognised by the German Commission E as a gargle for mild inflammation of the mouth and throat, while flower tea was traditionally drunk as a diaphoretic, mildly diuretic and digestion-supporting remedy. Ripe, frost-touched fruit is also the base of the classic sloe liqueur. Importantly, the stones contain the cyanide-releasing glycoside amygdalin and must never be crushed or chewed; the leaves, too, are unsuitable for tea. The fruit flesh itself and the dried flowers are unaffected by this concern.
Infusion of dried sloe fruits used as a mouthwash or gargle for mild inflammation of the oral and pharyngeal mucosa. The German Commission E issued a positive monograph for Pruni spinosae fructus for this external indication.
Preparation & dosage
Pour 200 ml boiling water over 2–4 g dried, stoned fruits, steep 15 minutes, strain. Cool and gargle several times daily.
- Dry amount
- 2–4 g
Flower infusion for digestive complaints, mild constipation and bladder-kidney support. Recorded in folk medicine for centuries; Commission E negative monograph due to insufficient efficacy evidence, no safety concerns identified.
Preparation & dosage
Pour 200 ml boiling water over 1–2 g of dried flowers (harvested just after opening), steep 10 minutes, strain.
- Dry amount
- 1–2 g
- Doses per day
- 2×
Sloes eaten raw after the first frost or processed as jam and juice. Frost (or freezing) reduces the tannin content from approx. 10 g/l to below 5 g/l and alleviates the extreme astringency. Traditionally used as a tonic after infectious illnesses.
Sloe liqueur or spirit (sloe gin) from ripe, frosted fruits; used in folk medicine as a digestive bitters and restorative after exhaustion. No therapeutic proof, but part of a long European tradition.
Flower infusion traditionally used as a diaphoretic and febrifuge for colds. PFAF documents diaphoretic and febrifuge properties of the flowers.
Sources: [2]
Flower infusion used in folk medicine as a mild diuretic for bladder and kidney complaints. PFAF describes the flowers as aperient, diuretic and depurative.
IMPORTANT: The stones of sloes contain the cyanogenic glycoside amygdalin. Never crush or grind the stones; use the fruit flesh only. Leaves also contain amygdalin – do not use as tea. Fruits are strongly astringent before frost; much milder after frost or freezing. ASPCA classification (accessed 2026-08-10): toxic to dogs and cats. The ASPCA classifies the whole genus this way.
Insufficient safety data for medicinal use during pregnancy. Sloe fruits as food (without stones) in customary amounts are safe.
No systematic data. Fruits as food in small amounts are acceptable.
Children under 18: insufficient safety evidence for medicinal use. Fruits as jam in small amounts are safe; stones must be avoided.
Contraindications
- Hypersensitivity to Rosaceae.
- Crushed or ground stones (amygdalin release causes cyanide poisoning).
Harvested part: flowers (April-May), fruits after frost (late autumn)
- Time of day:
- Morning on dry days; harvest flowers shortly after opening, before the pollen disperses.
- Drying:
- Spread immediately in a thin layer and dry in shade or dehydrator at max. 35 °C. Flowers are very delicate.
- Storage:
- 12 months — Store in paper bags or airtight jars in a cool, dark place.
- Time of day:
- After the first frosts (or after freezing); ideally harvest in the morning.
- Drying:
- Dry stoned fruits at 50–60 °C or freeze. Always remove the stones during processing.
- Storage:
- 24 months — Frozen up to 2 years; dried in dark jars 1 year.
- AmygdalinGlycosideSeed
Cyanogenic glycoside in the stones; enzymatically cleaved to hydrogen cyanide upon crushing. Only trace amounts in the fruit flesh.
- Gerbstoffe (Tannine)TanninContent: 0.5-1.0 %Fruit
Primarily responsible for the extreme astringency before frost; content drops from ~10 g/l to below 5 g/l in the juice after frost.
- Flavonoide (Quercetin, Rutin)FlavonoidFlower
Flavonoids in the flowers; contribute to astringent and antioxidant properties.
- AnthocyaneFlavonoidFruit
Responsible for the deep blue to black colour of ripe sloes; antioxidant.
- Triterpene und SteroleOtherFlower
Secondary metabolites of the flowers; exact pharmacological role not yet fully established.
- Organische Säuren (Äpfelsäure, Citronensäure)Phenolic acidFruit
Major acids of ripe fruits; responsible for the tart flavour profile and contributing to preservation.
- PektinPolysaccharideFruit
Gel-forming polysaccharide; important for the production of jams and jellies from sloes.
- [1]MonographKommission E Monographie – Pruni spinosae fructus – Äußerliche Anwendung bei Mund-/Rachenentzündungen (via PFAF, Arzneipflanzenlexikon)(accessed: 2026-05-21)
- [6]MonographASPCA Animal Poison Control — Cherry (Prunus spp.)(accessed: 2026-08-10)
- [7]MonographCliniTox Giftpflanzen — Prunus spinosa L.: schwach giftig (+) (Institut für Veterinärpharmakologie und -toxikologie, Universität Zürich)(accessed: 2026-08-10)
- [2]BookPlants For A Future – Prunus spinosa(accessed: 2026-05-21)
- [5]BookArzneipflanzen-Lexikon – Schlehdorn (Prunus spinosa)(accessed: 2026-05-21)
- [3]WikipediaSchlehdorn (Wikipedia DE)(accessed: 2026-05-16)
- [4]WikipediaPrunus spinosa (Wikipedia EN)(accessed: 2026-05-21)