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Jojoba is native to a triangle of the Sonoran Desert whose corners are roughly Los Angeles (California), Phoenix (Arizona), and the southern tip of Baja California (Mexico). This area encompasses some of the earth's most inhospitable land: in some places rainfall is as sparse as 3 inches (8 cm) a year, and temperatures soar as high as 130°F (54°C). Few crops could survive this blistering environment, but among the rocks, gravel, and sand, jojoba endures.
The severity of its native habitat endows the plant with a
rugged, robust nature. Some of the most northerly jojoba plants get snowed on in
winter. Some westerly ones grow in sand dunes, often exposed to ocean spray,
which few other species can survive. The easterly ones are in dry deserts where
some years rain refuses to come at all.
Distribution of native jojoba in the
southwestern United States and northwestern Mexico. The plant occurs naturally
over a range of latitudes and altitudes. It extends from the coast to inland
deserts. The germplasm through much of this area still remains to be collected
and evaluated. (Office of Arid Lands Studies, University of Arizona, based on an
original map by R. Turner)
Appearance
Although frequently stunted to a height of 2-3 feet (60-90 cm) by the harshness of its environment or by heavy browsing by wildlife, jojoba can grow to more than 15 feet (5 m) in well-watered sites and in plantations. An evergreen, it has thick gray-green leaves and brown seed. Its natural lifespan appears to be at least 40 years. (Jojoba bushes with more than 200 rings are in fact known in the wild, although it is not known whether these represent annual rings or just growth spurts after heavy rains.)
The leaves are endowed with a dense covering of wax plates -
a cuticular barrier that reduces moisture loss and protects against fungi,
insects, and pollutants.
Most native jojoba plants grow among palo verde, mesquite, ocotillo, and saguaro in the desert foothills and washes. Their leaves, like soft leather ovals, stand out stiffly in pairs, creating a shield held up by a network of sturdy grey branches. Often finding little soil, they nestle together as compact spheres. On better sites, however, they resemble olive trees in their shape and color.
Taxonomy
Early in the nineteenth century, at the botanic garden of Berlin, a package of plants collected in Baja California was confused with another collected in China. When the American plants were described they were assumed to be Chinese. One, described by the garden director Johann H. F. Link in 1822, was jojoba. He named it Buxus chinensis.
In 1844, American botanist Thomas Nuttall described jojoba collected from San Diego. He put it in a new genus, Simmondsia, named to honor the English naturalist, F. W. Simmonds, a colleague who had died while studying the plants of Trinidad 18 years earlier. Nuttall's full designation was Simmondsia californica.
Other names and descriptions for jojoba appeared at about
the same time, as well as later that century, and in 1912 the multiplicity of
names was clarified by the Austrian botanist Camillo Karl Schneider. He retained
Nuttall's generic name Simmondsia and Link's specific name chinensis, resulting
in the full botanic epithet: Simmondsia chinensis (Link) C. K. Schneider.
Despite the geographical inconsistency, this is currently jojoba's formal name.
These early botanists placed the plant in the boxwood
family, Buxaceae. However, in 1898 the Belgian botanist van Tieghem suggested
(on the basis of the dioecious breeding system, floral morphology, and wood
anatomy) that jojoba be put into a family of its own, Simmondsiaceae. In recent
times this view has been championed by several taxonomists and is beginning to
gain acceptance among botanists (Information from R.F. Thorne).
Flowers
Jojoba bushes are either male or female. The males produce
pollen and have flowers containing only stamens. The females produce the fruit
and seeds and have flowers containing one ovary with three ovules. Tendencies
toward hermaphroditism are noted in a few male bushes. These produce all grades
of perfect flowers: from those with an undeveloped pistil to those with a
complete ovary that can even yield fertile seed.
The sex of a young jojoba plant cannot be judged until the
first flower buds appear. In precocious individuals this may be in the summer of
the first year, whereas in slow plants it may take until the fourth year.
Typically, flowering occurs at alternate nodes along the branches, although some plants produce flowers at each node and others produce them at every third node.
Male flowers occur in clusters; female flowers are commonly solitary. However, in certain populations many of the female bushes have clustered flowers. As many as 50 female flowers in a single cluster have been recorded.
Female flowers have no petals or odors to attract insects, and the plant depends almost entirely on wind for pollination. Although honey bees and a variety of other insects are often seen foraging for pollen on the male and on the hermaphroditic flowers, they rarely visit female flowers.
Floral buds appear on the current season's growth, mainly in the summer and the fall. They usually open in the following spring. This flowering is triggered by the stress of cold or drought or both. Unseasonal weather - for example, a cool fall followed by a warm, wet winter period - can trigger early flowering, which often leads to loss of the crop if the weather turns harsh.
The fruits, which are about the size of acorns, are greenish at first but turn brown as they mature, sometime during the early summer. They contain one seed, occasionally two or three. Eventually, the flesh and outer husks dry out, shrink, split, and peel back to expose the soft-skinned brown seed or seeds inside.
Roots
To help survive drought, the plants have an exceptionally deep root system that taps into the underground moisture. Bushes a mere 1-2 years old have been found with roots 12-16 feet (4-5 m) deep. Some mature shrubs have been found with roots penetrating as far as 40 feet (13 m) into the soil.
Seedlings devote most of their energy to producing a taproot - a natural survival mechanism in deserts where surface soil dries out rapidly. A seedling's taproot may grow as much as an inch (2.5 cm) a day. Often young plants have roots 10 times longer than the height of the plant above ground. Seedlings normally take about 21 days to break through the soil, by which time they can have roots 18 inches (46 cm) deep.
A strong taproot may be essential to jojoba's survival in many desert areas, but the plant uses water from deep soil layers only as a reservoir to resist and recover from drought stress. Some 80 percent of its feeding roots are in the top 2.5 feet (80 cm) of soil.
A symbiotic fungus, tentatively identified as Glomus deserticola, has been found on jojoba roots in its native state. On citrus trees, a closely related mycorrhizal fungi, Glomus fasciculatus, is known to stimulate the uptake of phosphorus, zinc, copper, and many other elements. The jojoba mycorrhiza probably does the same; in laboratory experiments, plants inoculated with it have experienced increased growth rates, reduced transplant shock, and heightened disease resistance.
Latitude
Natural populations occur between 23° and 35°N latitude. However, jojoba flowers and sets seed well near Fortaleza, Brazil (latitude 4°S); Mombasa, Kenya (4°S); San Jose, Costa Rica (10°N); and Erkowit, Sudan (18°N). It would appear, therefore, that differences in latitude and daylength are not important limitations to jojoba cultivation.
Temperature
Jojoba tolerates extremely high temperatures: during the summer, daily shade readings of 95°-120°F (35°-48°C) are common in its natural habitat. Often the ambient air temperature is 120°F (48°C) and soil temperature 150°F (65°C). However, temperatures above 100°F (38°C) appear to be of no advantage to the crop, and may actually decrease its productivity because they cause the stomata to close, thereby stopping vegetative growth.
When selecting a site, it is important to consider low-temperature hazards. Aberrations in weather can cause freezes in most desert areas - on occasion. Ideally, the land should be frost free. Jojoba can grow where occasional light frosts occur, but in such areas the plants should be grown on slopes (preferably facing the sun) or where there is good air drainage. Valley bottoms where cold air collects must be avoided. Sites where temperatures frequently fall bellow 23°F (-5°C) for prolonged periods should never planted to jojoba.
Hardened plants can endure 16°F (-9°C) without sustaining longterm damage, but flower buds and any newly set seed can be damaged at 28°F ( - 2°C) and killed at 22°F (-6°C).
Moisture
A desert native, jojoba thrives under soil and moisture conditions unsuited to many agricultural crops. Most natural stands grow in areas receiving 8-18 inches (200-460 mm) of annual precipitation. However, although it has been called "the plant that doesn't get thirsty," it does require moderate amounts of water for quick plantation establishment and for best yields. In addition, soil moisture is critical from spring to early summer, the period in which flowering and fruit development occur.
For economic reasons, 18-24 inches (460-610 mm) of annual moisture appears to be most suitable for establishing plantations, and, in most areas, is probably needed to ensure commercial success. However, where drainage is good, extra water may not be detrimental: jojoba has been observed growing satisfactorily in sand where rainfall is 50 inches (1,270 mm) annually.
Wherever the plant is grown, good drainage is vital; jojoba cannot survive waterlogging. Flooding twice destroyed test plots near Yuma, Arizona, and most plants were killed when a test plot in Western Australia was flooded for less than two days. Losing an established plantation would be a financial catastrophe, so the possibility of a "freak" or "100-year" flood should be considered when choosing a plantation site.
Jojoba's native habitat covers areas where the main rainy seasons are in winter and/or summer. There seems to be no difficulty growing the crop in other regions that display either pattern. For example, jojoba is developing well in both the eastern (summer rainfall) and western (winter rainfall) parts of Australia. Mombasa, Kenya, gets two monsoons a year, and four-year-old plants there flower twice a year, each time following the rains.
Soil
In the Sonoran Desert, the biggest and most vigorous jojoba plants are on sloping, well-drained soils with silt and clay in the lower horizon. In cultivated stands, some plants are successful on sandy soils, others on silt-loam. Heavy clays may be suitable in some areas, but only if internal drainage is high. The plant cannot withstand soils with poor porosity. For instance, heavy bottomland soils prone to flooding are not suited to it.
Extensive measurements made in wild jojoba populations in Mexico and the United States have shown the plant thriving in soils ranging from pH 5 to 8, indicating that, within reason, soil acidity or alkalinity is probably not a limiting factor.
Salinity
The buildup of salt - because of excessive irrigation and high surface temperatures - is a common problem of arid lands. Jojoba tolerates water of low quality, provided its application is wisely managed and the soil drainage is adequate. In California, plants are growing satisfactorily with water containing 2,000 parts per million of salts. In one large planting by the Salton Sea, young seedlings are growing without obvious sign of stress, in spite of a brackish water table just 6 feet (1.8 m) below the surface. When tested in the laboratory, one variety of jojoba showed no reduced growth of flower production at a soilwater salinity of about 7,000 ppm.(Information from D. M. Yermanos) Jojoba's tolerance of saline water has also been demonstrated in Israel, for example, at the commercial and experimental plantings at Kalia, near the Dead Sea.
However, some jojoba lines apparently do not survive salt stress well because leaf damage and retarded growth have been noted in some areas. The type of salt appears to be more significant than the amount: high sodium adsorption ratios (SAR) should be avoided or need to be carefully managed. Further, long-term tolerance to salinity in plantations has not been demonstrated. Salinity buildup in the root zone could be a future problem for plantations with restricted drainage that use saline water.
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