Jojoba (Simmondsia chinensis)
Main sources: Dimmit, Mark, "Simmondsiaceae (jojoba family)," in Steven Phillips and Patricia Comus, eds., 2000, A Natural History of the Sonoran Desert, pp. 256-7, Arizona-Sonora Desert Museum Press, Tucson; Epple, Ann, 1995, A Field Guide to the Plants of Arizona, Helena, Montana: Fountain Press, p. 137; Shreve, Forrest & Ira Wiggins, 1964, Vegetation and Flora of the Sonoran Desert, Vol. 1, Palo Alto: Stanford University Press.
Jojoba is a woody evergreen shrub whose leaves are leathery, thick, grayish green in color, and elliptical in shape, reaching up to 1 1/2" in length. Distinctively, these leaves are vertically oriented (note the banner photo closeup of a single large bush, above), an adaptation which lessens sun impact at summer high noon, while exposing each leaf to the less extreme temperatures of morning and evening (Dimmit, cited above). Evergreen shrubs are few in the Sonoran Desert (Creosotebush is another example), their occurrence reflecting the ability of the plant to conduct its leaf functions both in cold months and in dry ones. Nearly all desert evergreens are confined to deserts having mild, rainy winters like our own Arizona Uplands.
Jojoba plants are dioecious -- female and male flowers occur on separate plants -- and the male pollen buds may be seen in the two images stacked to the right. These are pale-greenish in color, occurring in a dense cluster. Blossoming times for Jojoba are extremely variable (from December to July), depending on weather variations. the budding images at right were taken in late February 2004, following a couple of good winter rains. Click on the top image to enlarge it.
(Click on the image at left to enlarge it)
The seeds eventually ripen to a strong brown color, as you can see in the image to the right. Click on the image to enlarge it: you will then see, on one of these female plants, three of last year's nuts, now dessicated -- one at the lower left, one in the center, and one at upper right-center of the photograph.
Jojoba nuts contain a liquid wax which is highly resistant to spoilage and stable under high temperatures. As such, it is a very high quality oil, used for industry and also in cosmetics. Difficulties in harvesting have limited its commercial development.
This shrub may reach quite large sizes, occasionally more than 7 feet tall. The photographs below give an indication of various sizes: below left, a very large plant towers overhead at the base of the Yellow Cliffs of Hot Springs Canyon; below middle, two much more typical size bushes on a ridge above the Canyon; below right, a young plant sprouts in the shadow of a larger Jojoba. (Click on each image to enlarge it.)
Jojoba foliage is browsed by deer and javelina (and also cows). Various rodents, rabbits, and large birds eat the nuts, but the wax inside is largely indigestible, and acts as a laxative in humans.
According to Shreve & Wiggins (cited above), Jojoba seems especially suited to the North slopes of granitic hills and upper Bajadas of the Sonoran Desert, but in our particular area, we find it mainly in the Galiuro Volcanics hills and rocky slopes near the Yellow Cliffs of Hot Springs Canyon, where (especially on North-facing slopes) it is in some places the dominant plant. We also see lots of very small plants here, a sign that this habitat is well suited for Jojoba. For example, looking down toward the stream from slopes above, most of the plants below, in the foreground as well as the immediate adjacent slopes further below, are Jojoba: