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Products > Quillaja saponaria
Quillaja saponaria - Soapbark Tree
Image of Quillaja saponaria
[2nd Image]
Habit and Cultural Information
Category: Tree
Family: Quillajaceae (previously in Rosaceae)
Origin: Chile (South America)
Evergreen: Yes
Flower Color: Greenish White
Bloomtime: Spring/Summer
Height: 25-40 feet
Width: 10-15 feet
Exposure: Full Sun
Summer Dry: Yes
Irrigation (H2O Info): Low Water Needs
Winter Hardiness: 20-25 F
May be Poisonous  (More Info): Yes
Quillaja saponaria (Soapbark Tree) - A slender, upright evergreen tree that grows to 30-45 ft. tall with pendulous branchlets. The bright green oval leathery leaves are 1-1 1/2 inches long and 1/2 to 3/4 inches wide with slightly toothed margins but nearly entire towards the leaf base. Greenish white star-shaped flowers, about 1/2 inch across, are freely produced at the branch tips in late spring to mid-summer and are followed by the 3/4 inch wide 5 lobed pinwheel shaped fruit which is of leathery texture and matures in the fall. Plant in full sun, water deeply and infrequently - can withstand drought conditions but looks more lush when given occasional deep irrigation or when planted in an irrigated lawn. It is also tolerant of poor soils. Quillaja is reliably cold hardy into at least the low 20s F and some suggest as low as 10 F. It went through our December 1990 freeze without damage with short duration temperatures down to 18 F (Sunset suggests zones 8,9,13-24). Young plants tend to be bushy and need occasional pruning when young but eventually form narrow, almost columnar, trees that is ideal for narrow confines. Another usage is as a tall hedge. The Soapbark Tree is also noted as good for attracting beneficial insects, attracting to the garden such insects such as lacewings, hoverflies, lady beetles and wasps. This forest tree from Chile, where it is found in dry, poor soils up 6,500 feet elevations, is often called Soapbark as the bark is harvested to extract saponins and other foaming agents and most recently there has been interest in the use of these saponins for use as an adjuvant with vaccines and it is being studied for such use for a COVID-19 vaccine. These saponins also are the reason this plant can be found on poisonous plant lists and Quillaja saponaria is listed in Poisonous Plants of California (Thomas Fuller and Elizabeth McClintock, UC Press 1986) because of toxic saponin glycosides. As noted in this book, these toxins characteristically affect cold blooded animals but if the gastrointestinal tract of warm blooded animals has been injured, they can be absorbed. It is further noted however that plants containing saponins are typically bitter to the taste and so are rarely browsed. The specific epithet is in reference to these compounds while the name Quillaja (pronounced "key - ya - ha") is from the indigenous Chilean name Quillai (pronounced "key ya hey"), a modification of the word 'quillean', meaning "to wash". Up until recently this plant was considered to be in the rose family, the Rosaceae, but more recently it has been put by taxonomists in its own family, the Quillajaceae, that only has the one genus with two extant species. Quillaja saponaria was listed in Harry M. Butterfield's 1964 manuscript Dates of Introduction of Trees and Shrubs To California as being first introduced into California in San Francisco around 1878 as reported in the San Francisco Bulletin that year. The California Horticulturist and Flora Magazine of this same year reported that this bulletin announced that a unnamed "gentleman from Valparaiso", who previously had farmed in Alameda county, arrived by steamer from Chile with seeds that were to be distributed to subscribers of the bulletin. Other seed that arrived in this shipment included Cryptocarya rubra (now C. alba), Tara (Caesalpinia) spinosa and Maytenus boaria. In Peter Riedel's (1873-1954) Plants for Extra-Tropical Regions, published in 1957 after Riedel's death, Riedel also notes a later introduction by the Bureau of Plant Industry, a division of the U.S. Department of Agriculture, with the number BPI 26325-1909, indicating it was introduced by them in 1909. Riedel notes that at the time he wrote the entry for this plant, likely in the early 1950s, there was a large tree at the east entry to the University of California Berkeley campus that uncharacteristically had a broad canopy. In Woodbridge Metcalf's 1969 Trees of the Berkeley Campus it is noted that this large spreading specimen was planted in 1885 near the Crescent Drive west campus entrance off of Oxford Street. Trees noted elsewhere in San Francisco and Santa Barbara are more characteristically upright and suitable for narrow spaces and for use as street trees. There are several fine specimens of this tree in Santa Barbara and it is from these trees that we have collected our seed and grown this plant since 1985. 

This information about Quillaja saponaria displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.