While the castor bean (Ricinus communis) is known for its extremely poisonous beans and invasive nature, it also grows into an ornamental 8- to 15-foot tall, tropical shrub in only three to four months. Thriving in U.S. Department of Agriculture plant hardiness zones 8 through 11, the castor bean plant dies at the first frost, but the seeds will survive freezing weather as far north as Minnesota, in USDA zone 4a.
Germinating Castor Beans
Castor beans require special treatment for quick germination. Soak the beans overnight in warm water. Plant in sterile seed-starting mix, and place in a location where the temperature remains above 75 degrees Fahrenheit until the seeds germinate in 10 to 21 days. Transplant the seedlings into a well-drained, sunny part of the garden. Keep the soil moist, but not waterlogged, as the plants grow to maturity.
While some sources recommend scarifying the beans by lightly sanding the outer shell, all parts of the castor bean are extremely poisonous. Don't risk exposure to the dust generated by even the lightest sanding. Keep castor beans and plants out of reach of children and pets. If you can't resist growing castor beans, deadhead the flowers to prevent accidental poisoning and avoid spreading the plant beyond your garden.
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