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Alder Buckthorn

Frangula alnus

Also known as Black Dogwood, Frangula, Arrow Wood, Glossy Buckthorn (regional), Rhamnus frangula

At a glance
Family
Rhamnaceae (buckthorn family)
Type
Deciduous shrub or small tree
Parts used
Bark, dried and aged at least one year
Size
6 to 16 feet tall (2 to 5 meters)
Bloom
Small, star-shaped greenish-white flowers in late spring to early summer
Habitat
Damp woodlands, hedgerows, fens, and riverbanks across Europe, western Asia, and North Africa; naturalized in parts of North America
Acquisition
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Key benefits

Eases occasional constipation
Traditional purgative bark
Supports wildlife garden habitat
Long-standing apothecary staple

Traditional uses

For centuries, apothecaries across Europe kept a jar of alder buckthorn bark on the shelf as one of the most dependable purgatives in the herbal cabinet, a gentler cousin to the American cascara sagrada. Country healers knew a secret the shrub itself does not give up easily: the freshly stripped bark is too harsh and nauseating to use, so it was set aside and aged for a full year, or gently dried and warmed, before it was ever considered fit for the teapot. Once tamed by time, the bark was traditionally steeped into a mild decoction and reached for only occasionally, to nudge a sluggish digestion back into rhythm. It found its way into old pharmacopoeias under the Latin name Frangula, meaning to break, a nod to how easily its slender branches snap.

Growing guide

Sun
Full sun to partial shade; tolerates the dappled light of a woodland edge
Soil
Prefers moist, humus-rich, slightly acidic to neutral soil, but adapts well to boggy or occasionally waterlogged ground
Water
Steady moisture; thrives near ponds, ditches, and streambanks and does not like to dry out completely
Planting
Set out container-grown saplings in autumn or early spring, spacing them several feet apart if planting as a hedge or wildlife thicket; established shrubs need little attention beyond an occasional light prune

Fresh to dried

Harvest
Bark is traditionally peeled from branches or the trunk in spring, when the sap is rising and it lifts away most easily
Drying
Spread the strips in a single layer away from direct sun until fully dry and brittle; fresh, unaged bark is considered too harsh for traditional use
Storage
Once dry, the bark must be set aside and aged for at least a full year in a cool, dark, airtight container before it is considered ready; older herbalists dated their jars for exactly this reason
Best forms
Properly aged, dried bark for a simple decoction, or a commercially prepared standardized extract
Pairs well with
  • Ginger
  • Fennel
  • Licorice root
Substitutes
  • Cascara sagrada
  • Senna leaf
Choose it when

For the rare evening when the body asks, gently, for a nudge back toward balance.

Did you know?

Alder buckthorn is the sole food plant for the caterpillars of the brimstone butterfly, so gardeners who plant it are, in effect, planting a nursery for one of spring's first butterflies on the wing.

Safety

Fresh, unaged alder buckthorn bark is toxic and can cause severe cramping, nausea, and vomiting; it must be dried and aged for at least one year (or artificially aged with heat) before it was traditionally considered safe to prepare. The bark contains anthraquinone glycosides and was never used as a long-term remedy, since prolonged use of any anthraquinone laxative can lead to dependency, electrolyte and potassium loss, and worsening of bowel function over time. It was traditionally avoided during pregnancy and breastfeeding, in children, and by anyone with inflammatory bowel disease, Crohn's disease, ulcerative colitis, or intestinal obstruction. Because potassium loss from overuse can affect heart rhythm, it was also traditionally avoided alongside heart medications such as digoxin, diuretics, or corticosteroids. As with any herb that acts this strongly on the body, please speak with a qualified healthcare provider before considering its use, especially if you take other medications or have an existing health condition.