Jatropha

Siting: Jatropha curcas grows in tropical and subtropical regions between 30°N and 35°S at low elevations up to 500 metres, flowering independent of day length so that blooms can appear at any time of year once rainfall triggers them. It requires full sun, is intolerant of shade and frost, and performs best where temperatures stay between 20°C and 28°C, since very high heat can depress yields.

Watering and soil: The shrub survives on as little as 250 to 300 mm of annual rainfall but needs at least 600 mm to flower and set fruit, with 1 000 to 1 500 mm considered optimal for seed production. It grows best in aerated sandy or loamy soils at least 45 cm deep with a pH of 6.0 to 8.5, avoiding heavy clay or waterlogged sites, and tolerates saline irrigation water.

Propagation: Jatropha is direct-sown or transplanted from nursery-raised seedlings or cuttings, with seedlings and cuttings achieving survival rates above 80 percent compared with less than 50 percent for seed sown directly in the field. Cuttings establish and yield earlier but lack the taproot that seed-grown plants develop, leaving them less able to draw on deep soil moisture and less stable on windy sites; mulching and legume cover crops under this perennial crop help maintain soil health.

Excess rainfall beyond the optimum range increases the risk of fungal attack, particularly where soils do not drain freely, and the plant will not tolerate waterlogged ground. Its ability to survive in very poor, dry soils does not mean that high yields can be expected under such marginal conditions.

Industrial: Jatropha curcas is grown chiefly as an oilseed crop; its seeds contain 27 to 40 percent oil, averaging around 34 percent, which is pressed and converted into biodiesel for diesel engines. The protein-rich press cake left after oil extraction can be used as fish or animal feed once detoxified, burned as biomass to generate electricity, converted to biogas, or applied as an organic fertilizer.

Other uses: The oil has also historically served as a fuel for lamps, and plantings of the crop have been studied for their potential to sequester carbon in arid regions.

Jatropha curcas originates from Central America and Mexico, though it is notably absent from the more humid parts of that native range. Despite its long history of cultivation for oil, the species has never been properly domesticated, which leaves its productivity highly variable from one growing environment to another.