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How to Grow a Castor Bean Plant

The castor bean plant, also known as Ricinus communis, is native to Africa and grown as a shrub or tree in tropical areas. It was introduced to more temperate regions of the world as a fast-growing annual. Castor bean plants can be sown directly into the ground after the danger of frost has passed or indoors a few weeks before the last frost. Castor bean plants will grow up to 10 feet tall in a single summer and will die as soon as the first frost of fall appears. It is fairly easy to grow a castor bean plant.

Soak your castor bean seeds in water for 24 hours before planting.

Plant your castor bean seeds indoors six to eight weeks before the last frost date in your area. Use a well-draining potting mix and quart-sized pots. Sow 1 seed per pot.

Water the soil thoroughly and keep it evenly moist, but not waterlogged. Germination should occur within a one to two weeks.

Amend the soil in your garden with equal parts of compost and rich garden loam before transplanting your castor plant seedlings. Transplant into the garden after danger of last frost has passed. Pick a location that receives nearly full sunlight.

Fertilize your castor bean plants every four to six weeks during the growing season with a slow-release fertilizer. Read the directions on the bag for the amount to apply.

Provide 1 inch of water per week for your plant during periods of drought. Make sure you water the entire root zone, which can extend out to the edge of the foliage canopy.

Discard the castor bean plant after the first frost of the fall after all the foliage has burned back.


You may alternatively plant castor bean plants directly into your garden after the last frost date but your plants will not grow as large.

In garden zones 8 to 11, the castor bean plant may only die back to the ground in the winter. It will then regrow in the spring when the temperatures warm.


The castor bean plant and its seeds are extremely toxic. Keep children and pets away from the plant to prevent possible toxic ingestion of the plant parts or seeds.

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