The castor plant, Ricinus communis, is a large, fast-growing species whose seed is the source of a globally important industrial commodity. Cultivated for thousands of years, its history traces back to ancient Egypt, where the oil was used in lamps. Today, the oil’s unique chemical properties, particularly its hydroxylated fatty acids, make it indispensable for manufacturing specialized lubricants, hydraulic fluids, cosmetics, and pharmaceuticals. The castor bean possesses a dual nature: the oil is non-toxic and highly valued, but the seed contains ricin, a potent protein toxin. This combination of industrial value and inherent toxicity makes the geography of its cultivation a matter of global interest.
Primary Global Growing Regions
The majority of the world’s castor bean supply comes from a handful of countries concentrated in tropical and subtropical zones. India is the dominant global producer, consistently supplying a vast portion of the world’s total output. In 2023, India accounted for nearly 90% of the total recorded global production, concentrated primarily in the states of Gujarat, Andhra Pradesh, and Rajasthan.
Following India, the output drops sharply, but key secondary producers maintain important roles in the global supply chain. Mozambique currently ranks as the second-largest producer. Brazil, an historically significant producer, holds the third-place position, often growing castor as a second crop after staples like soybeans. China typically ranks fourth among the world’s largest suppliers, while Thailand and Ethiopia also contribute meaningful amounts to the international market.
Climate and Environmental Needs
Successful cultivation of the castor plant requires a long, warm growing season. When grown as an annual in temperate areas, the plant needs a frost-free period spanning 140 to 180 days to fully mature. Optimal temperatures for vigorous growth and high yields range between 68 and 80°F (20–26°C). High heat is tolerated, but sustained temperatures above 95°F (35°C) can limit the development of female flowers and reduce seed set.
The plant thrives in rich, loamy soils that are well-drained and possess a permeable subsoil. While the crop is known for its drought-hardy nature once established, initial growth requires consistent moisture. Regions receiving approximately 50 to 75 cm of rainfall are well-suited, as excessive moisture can lead to overgrowth of vegetative parts rather than higher seed yield. The plant’s extreme sensitivity to frost is a limiting factor for commercial cultivation, as frost will terminate the growing cycle.
Limited Cultivation in the United States
The United States is a significant global consumer of castor oil, relying heavily on imports, mainly from India, to meet its industrial demand. Domestic commercial cultivation is currently minimal or non-existent, having largely ceased in the early 1970s. Historically, production peaked in the 1950s and 1960s, driven by government contracts for the oil’s use in military lubricants and hydraulic fluids. Texas, particularly the Plainview region, and parts of Oklahoma were the primary growing areas during this period.
The decline of US cultivation was primarily due to high domestic labor costs and the instability of the world market supply. A secondary factor was the safety hazard posed by the ricin toxin and the allergens present in the seed meal, which required specialized handling. Today, any domestic production focuses on experimental or niche programs, such as those in Texas and California, exploring new mechanized harvesting methods or genetically modified, non-toxic varieties.