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How to Plant Castor Bean Seeds

By Sarah Morse ; Updated September 21, 2017

Castor bean plants have been around for over 4000 years. They can grow 4 to 6 feet tall with lobed leaves that can reach 3 feet in width. Castor bean plants are perennial in USDA zones 9 to 11, which means they overwinter where the temperature does not drop below freezing. In cooler climates, however, they grow well as an annual. Planting the seeds for this plant is not difficult as long as you know how to create the right environment for them.

Start the germination process in March by soaking the seeds in warm water overnight. This will help clean the seed of any debris before planting and soften the seed coat.

Fill a 3-inch diameter pot with half peat and half perlite for each seed you wish to plant. Plant a single seed 2 inches deep in each pot.

Water the seeds, keeping them moist but not soaked, as they begin to grow. Wait until they grow 6 inches tall and transplant them to 5-inch diameter pots filled with the same potting medium.

Choose an area with full sun and fertile, moist, well-drained soil to plant the seedlings. Prepare this area by digging into the soil with a spade or trowel, breaking up clumps and removing rocks.

Plant the castor bean seedlings outside once the danger of frost passes. Space them 3 to 6 feet apart, and water them regularly.


Things You Will Need

  • Container
  • Warm water
  • 3-inch diameter pots
  • Pet
  • Perlite
  • Water
  • 5-inch diameter pots
  • Spade or trowel


  • Castor bean seeds are poisonous for both humans and animals. Keep them out of reach of children and pets.
  • As the plant grows, pinch off the seed pods, and throw them in the trash to avoid accidental poisoning.

About the Author


Sarah Morse has been a writer since 2009, covering environmental topics, gardening and technology. She holds a bachelor's degree in English language and literature, a master's degree in English and a master's degree in information science.