Quillaja saponaria aka Murillo's Bark

Quillaja saponaria is an evergreen tree in the Quillajaceae family. Its common names include quillay, soap bush, and soap-bark tree. Kew places its native range in central Chile. It grows on the western slopes of the Andes. Oregon State also reports a range north to Peru. This tree comes from warm temperate to subtropical regions.

In gardens, it reaches about 30 feet [10 metres] tall. Its spread is about 16 feet [5 metres]. PFAF gives a larger size of 59 feet [18 metres]. Virginia Tech reports heights up to 75 feet [23 metres]. Growth is slow, and plants may form several trunks. The trunk can twist beneath a dense, uneven crown. Branches droop, though this becomes less marked with age. Smooth young bark becomes thick, rough, and plated. Its colour ranges from grey-brown to red-brown.

The leaves stay on the tree throughout the year. They grow alternately and reach about two inches long. Each oval leaf feels thick and leathery, with glossy green surfaces. Leaf edges may be smooth or bear a few blunt teeth. Young twigs carry fine hairs and vary from green to brown. White flowers form clusters at the ends of branches. Each flower has five parts and yellow anthers. PFAF records flowering from April to May, with insects providing pollination. Brown, leathery fruit opens into a five-pointed star. The capsules hold winged seeds called samaras. Fruit ripens in autumn and can remain through winter.

Grow this tree in fertile soil that drains well. It accepts sandy, loamy, and clay soils across a broad pH range. Full sun suits it, though Oregon State also permits partial shade. PFAF favours moist soil; Oregon State notes drought tolerance. Hardiness reports range from USDA zone 8 to zones 9–11. Young spring shoots can suffer damage from late frost. In Britain, mild sites may support shrubs or trees. Colder sites may need greenhouse shelter. It can serve as a hedge or grow beside sheltered walls. Oregon State reports unwanted self-seeding at the UC Santa Cruz Arboretum.

The inner bark contains saponins that produce a lather. People use these compounds in soap, shampoo, and textile cleaning. They also supply foam for some fire extinguishers. Andean people have used the bark for chest complaints. This history does not make it safe to swallow. PFAF reports internal toxicity and no known edible uses.