Simmondsia chinensis (Link) C.K.Schneid. (Simmondsiaceae)



Engraving of Simmondsia chinensis from Hooker's London Journal of Botany (1844; t.16). Leaves of Simmondsia chinensis growing in Oxford Botanic Garden.

Although not the most splendiferous or floriferous of plants at the Botanic Garden, this small shrub, which we grow in the Garden's Arid House, nevertheless has an intriguing story to tell.

Native to the southwestern deserts of the United States and to the northwestern deserts of Mexico, it is a small, xerophytic shrub (i.e., it is adapted to survive in an environment that lacks water). The thick, leathery leaves are covered with a waxy coating, which in harsh, arid environments, helps the plant to reduce moisture loss. The leaves are jointed at the base, so they can change their orientation, which ensures that the minimum leaf surface area is exposed to the sun.

The jojoba is usually dioecious, meaning that male and female flowers occur on separate plants. The small, yellow flowers are wind-pollinated. The re-curved bracts (modified leaves with a flower or flower cluster in the axil) and sepals (the green, leaf-like parts that enclose the flowers) direct pollen onto other flowers and aid pollen distribution. The shape and position of the leaves form a series of wind-tunnels, further helping the movement of pollen.

Why does a plant from the deserts of southern California have a species name (chinensis) that makes it sounds like it comes from China? It would appear that not only doctors have illegible handwriting; plant collectors suffer from the same problem. Johan Link, the botanist who originally named this plant, misread the handwritten collection label 'Calif.' as 'China'. Now, due to the rules surrounding plant names, chinensis is the appropriate specific epithet and has to be used.

The outside of this plant hides an important economic use that has helped save the whale. Sperm whale oil has long been used in the cosmetic and pharmaceutical industries, but jojoba seed contains a liquid wax, which has very similar properties and which is now widely used instead. However, despite the industrial suitability of the oil and wax products, it is proving challenging to cultivate the jojoba plant as a commercially viable crop. Not only do farmers have to wait until the plants are mature enough to bear flowers (typically 4 to 5 years), but they have to then weed out the male plants, which will not bear seeds, leaving just enough to provide the pollen required for efficient fertilisation. Crop improvement research programmes continue to investigate higher yielding strains, as well as maximising yield of existing stock.

Further reading

Gentry HS (1958). The natural history of jojoba (Simmondsia chinensis) and its cultural aspects. Economic Botany 12: 261-295.

Natural Resources Conservation Service (2014) Simmondsia chinensis (Link) C.K. Schneid. USDA.

Kate Pritchard