How to Grow Castor Beans
Castor beans have gotten a bad rap as a source of the poison ricin. The truth is that the beans have been used for thousands of years and the plants add a tropical touch to your garden.
What are Castor Beans?
Castor beans are not true beans. They are a member of the spurge family which includes poinsettias and euphorbias. They are called beans because the seeds resembles beans. The plants are tropical, native to eastern Africa, the eastern Mediterranean and India. They have spread to other tropical areas in the world. In fact they have become nuisances in some areas. They are hardy in zones 9 through 11.
The plants are large bushes/small trees, sometimes growing to 15 feet tall. In northern areas, they are grown as annuals, reaching 6 to 10 feet tall in a single growing season. They need full sun and well-drained soil. Castor bean plants have large, exotic looking leaves which sometines start out red and turn to green as they mature. Newer cultivars were bred so that the leaves stay red.
The plants have both male and female flowers so they are self-pollinating. The seeds are contained in fruit that is spiny and either green or red, depending on the cultivar. Each fruit has three chambers, each containing a seed. The seeds look like beans and have mottled colors of brown, gray, black, white and maroon. When the seeds are mature and ready to be dispersed, the fruits open and forcefully eject them.
How Poisonous are Castor Beans?
Only the beans are poisonous. They contain ricin which is one of the most poisonous substances known. It only takes consuming four or five beans to kill and adult. Even eating one or two beans can make you very, very ill. Symptoms of ricin poisoning include vomiting, bloody diarrhea, and convulsions. The symptoms can last for up to a week.
If you are growing castor beans and concerned that children or pets may eat the beans, simply remove the flowers so that the plants do not develop seeds. The rest of the plant is not poisonous. Only the seeds.
Is Castor Oil Poisonous?
Castor oil is not poisonous. The ricin toxin is water-based, so when the beans are crushed to release their oil, the water-based ricin stays with the “cake” or leftover material. It does not mix in with the oil.
Castor oil has been known and used for thousands of years. It was originally burned in oil lamps to provide light. Castor beans have been found in Egyptian burials. Castor oil has also been used for centuries as a laxative.
Does Castrol Motor Oil Contain Castor Oil?
Castrol oil originally contained castor oil. It’s how it got its name! Castor oil is an excellent lubricant. It was used in small engines where petroleum oil was too viscus. With the invention of modern synthetic motors oils, Castrol replaced the original castor oil with the new synthetics. However, the company does offer a version of their motor oil with castor oil for vintage engines.
How to Grow Castor Beans
Castor beans are often grown as ornamental plants, sometimes planted as a privacy hedge because of their size. Choose a location that gets full sun and has well-drained soil. Amend the soil with compost. These are large plants that require a lot of nutrients. If you are making a hedge with your castor beans, plant them at least 4 feet apart. Water well after they are planted. Once established, they are drought tolerant so they won’t require supplemental watering unless you experience an extended drought.
You should also stake your plants. Initially, they will grow up on a single stem. Their wide leaves act like sails, catching the wind and bending the plants over. Later in the season, they will develop their wide side branches which will act as stabilizers, preventing the wind from blowing the plants over. Until then, stakes will be needed to keep the plants upright.
How to Grow Castor Beans From Seed
Most gardeners start their beans from seed. Germination is very poor unless you give the seeds a little help. There are two ways to improve germination.
The first method is to soak them overnight before planting. This softens the tough outer shell, allowing water to penetrate and start the germination process. Remember, these seeds are highly poisonous, so you must be careful if you live with children and/or pets. I have cats so I use what I call the “cup & saucer” method. I fill a teacup with water and place whatever seeds I am pre-soaking in it. Then I place the matching saucer on top. This prevents my cats from drinking the water overnight while I am sleeping. Since I grow a lot of plants from seed and often am pre-soaking different seeds, I place the empty seed packet under the teacup, identifying what is soaking that cup.
You can also scarify the seeds. Using a coarse file, rub it once or twice across the seed coat. You don’t want to do it too hard or too deep because that could risk damaging the seedling inside. You want to just weaken the tough outer shell enough so that water can penetrate it and start the germination process. You can plant the scarified seeds immediately after you file them. There is no need to pre-soak them.
In zones 9 through 11, where the plants are perennial, after soaking or scarifying, you can plant the seeds directly in your garden in May. Plant them 1 inch deep and 8 to 11 inches apart. Germination should occur in 1 to 3 weeks. When the seedlings are 3 inches tall, you can thin them to 4 feet apart.
In colder zones, you will need to start your seeds indoors, 6 to 8 weeks before your last frost. Plant the seeds 1 inch deep in containers after you have pre-soaked or scarified them. Germination should occur in 1 to 3 weeks. You can transplant your seedlings into your garden after your last frost when the soil has warmed. In my zone 6 NJ garden, I transplant my seedlings at the end of May at the same time that I am seeding my cucurbits which also need warm soil. Plant your seedlings 4 feet apart.
© 2019 Caren White