Soap-Bark Tree, Soapbark

Quillaja saponaria

Physical Characteristics

Quillaja saponaria is an evergreen Tree growing to 18 m (59ft) by 6 m (19ft) at a slow rate. See above for USDA hardiness. It is hardy to UK zone 10 and is frost tender. It is in leaf all year, in flower from April to May. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers moist soil.

Distribution

S. America - Chile, Peru.

Habitats

Woodland Garden Secondary; Sunny Edge; South Wall. By. West Wall. By.

Edible Uses

None known

Medicinal Uses

Antiseborrheic Expectorant Skin Stimulant Soap bark tree has a long history of medicinal use with the Andean people who used it especially as a treatment for various chest problems[254]. The saponin content of the bark helps to stimulate the production of a more fluid mucous in the airways, thus facilitating the removal of phlegm through coughing[254]. The tree is useful for treating any condition featuring congested catarrh within the chest, but it should not be used for dry irritable coughs[254]. The inner bark contains about 9% of complex saponins, known collectively as 'quillajasaponin'[238]. It also contains calcium oxalate and tannin[238]. It has been used internally as a stimulating expectorant, though it can cause irritation and inflammation of the digestive tract and so is no longer considered safe[4, 238]. The internal use of this plant needs to be carefully overseen by a professional practitioner[254]. Sap bark tree is used as a source of compounds for the pharmaceutical industry[238]. It is still used externally as a cutaneous stimulant in the treatment of skin ulcers and eruptions, dandruff etc[171, 238].

Known Hazards

The plant is toxic if taken internally, tending to dissolve the blood corpuscles[171]. The bark, and possibly other parts of the plant, contains saponins[4]. Although toxic, saponins are very poorly absorbed by the body and so tend to pass through without causing harm, they are also destroyed by thorough cooking. Saponins are found in many plants, including several that are often used for food, such as certain beans. It is advisable not to eat large quantities of food that contain saponins. Saponins are much more toxic to some creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish[K].