Castor bean is a perennial shrub grown as an annual that grows best in tropical, subtropical, and warm temperate areas. It is native to eastern tropical Africa. The wild form of the plant may reach 9' in a season, whereas some cultivated varieties are smaller. Castor bean, especially cultivated varieties, can be grown as an ornamental, but great care should be taken since the seeds are extremely poisonous. Castor oil, derived from the castor bean, used to be a common household medicine. Currently, the oil has an industrial history as an ingredient in hundreds of products, from varnishes to brake fluids. It holds up well in both hot and cold temperatures, which makes it a standout among plant derived biodiesels. You can see castor bean in the Power Plants exhibit next to the Herb Garden.