Castor beans are an unusually versatile plant. They grow well in many different regions, but have different uses in cold climates than they do in warm ones. The castor bean requires little extraordinary care to blossom into a fragrant and fruitful plant, or to be an ornamental accent shrub.
Castor beans grow on their own in zones 8 through 9, and even in parts of zone 7. The plant reseeds itself in the springtime and spreads quickly. To get the maximum benefits of the castor bean plant, and a continuous life cycle, it requires a 140-to-180 day growing season.
In zones 10 through 11, the castor bean never reaches full maturity, but it does create a beautiful focal shrub with a tropical feel. Sow the seeds each spring to propagate castor beans in cold climates.
Even though the castor bean plant loves warm weather and long growing seasons, it has difficulty in extreme southern regions where the temperatures get over 100 degrees F for an extended period of time. However, the plants can survive and even thrive in these places with adequate watering. Once established, even drought does not harm the adult castor bean, although it will slow down in growth.
Stake the plant so that it stays off the ground. Castor bean plants get as big as 10 feet tall and have a bushy appearance. In perfect conditions, they can get to the extreme heights of up to 40 feet tall. Do not crowd them. Thin the seedlings to at least 12 inches between each plant. Plant the seeds in a rich, thick, loamy soil for good drainage.
Do not expect quick action from your castor bean plant in any climate. Germination is 10 to 21 days after planting, and full maturity requires up to five months.
Every part of the castor bean plant is toxic. Avoid planting this lethal beauty anywhere animals may get at it and attempt to eat it. Keep the plant and even the seeds away from small children. They are tempted to play with the beautiful seeds and can accidentally ingest them. Just a few seeds can kill a full-grown adult, but it only takes one or two seeds to kill a small child, or house pet.