Some plants, while they have roles to play in your landscaping, are hardly conversation pieces. For example, catmint can be an excellent ground cover, but rarely will a visitor walk onto someone's landscape and remark, "Wow, look at that catmint!" It is not designed to evoke such a response—instead, its purpose is to play a supporting role. Castor bean plants, on the other hand, have star power.
What gives castor bean plants their star power? Let's consider the three T's: tall, toxic, and tropical. It is because castor beans possess these three qualities (and more) that they are such interesting plants. Native to Africa and the Middle East, castor bean plants grow quickly, adding between 6 and 10 feet per growing season and featuring star-shaped leaves with vibrant red seeds. It can be planted straight into the garden in late spring or started from seed indoors about six to eight weeks before the last frost of the season.
|Botanical Name||Ricinus communis|
|Common Name||Castor bean|
|Plant Type||Herbaceous perennial|
|Mature Size||6–10 ft. tall, 2–4 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Moist but well-drained, rich|
|Soil pH||Neutral to acidic|
|Bloom Time||Summer, fall|
|Hardiness Zones||9–11 (USDA)|
|Native Area||Africa, Middle East|
|Toxicity||Toxic to humans, animals|
Castor Bean Plant Care
Castor bean plants are typically grown during the summer in most environments and will quickly reach sprawling heights, making them an eye-catcher in your landscape or a great option for a living privacy fence if grown together. However, height is just one attribute that makes castor bean plants stand out in your landscape. Their coarsely textured leaves create dramatic textural contrasts when placed alongside plants that have smaller leaves.
While the flowers on the castor bean plant are insignificant, the red seed capsules covered in spines do possess ornamental value. When these pods dry, they explode, turning the seeds that had been trapped within into projectiles. Even the seeds themselves are attractive, sporting an endless number of colors and patterns. It is perhaps the appearance of these seeds that give the plant its genus name, Ricinus, which translates to "tick" in Latin.
Many people are familiar with the fact that castor oil, an old-time laxative and purgative, is pressed from castor bean seeds. Additionally, some gardeners use castor beans in companion planting to serve as mole repellents. That being said, castor beans are not true beans—that's just a nickname. The plants belong to the Euphorbiaceae family, which makes them relatives of poinsettia plants and wood spurge. Since castor beans are tall, slim plants with large leaves that act like sails in the wind, be sure to stake them unless you've located them in a spot sheltered from high winds. Generally, the plants have no serious issues with pests or diseases.
Castor bean plants like full light and should be planted somewhere in your landscape where they get at least eight hours of sunlight a day. Avoid putting the plant below any towering trees, which can impact the amount of light it can get. Additionally, keep in mind that the more sunlight your plant gets, the fuller and more productive it will be.
Soil that is rich and moist will produce the best results for your castor bean plant. The mixture should be nutrient-dense and hold moisture well, but should not be boggy or easily waterlogged. If your intended planting zone isn't known for its soil, you can amend the mixture with some organic matter to increase the nutrient density.
Castor bean plants like soil that is consistently moist, but you should take care not to overwater them. Generally, the plant likes around 1 inch of water per week, either from rainfall or manual watering. Keep in mind, that amount may need to increase if you experience drought-like conditions or are having an especially hot summer.
Temperature and Humidity
True to their tropical nature, castor bean plants like warm temperatures and above-average humidity levels. If planted in the right USDA hardiness zones, your plant should be more than happy. As a rule of thumb, castor bean plants need soil temperatures of 50 degrees Fahrenheit to 64 degrees Fahrenheit to be planted outside and will grow and thrive best in an environment that ranges from 68 degrees Fahrenheit to 80 degrees Fahrenheit consistently.
For best success, feed your castor bean plant once a month with a general, all-purpose fertilizer.
Is Castor Bean Plant Toxic?
A poisonous plant in all its parts, castor bean's namesake "beans" (i.e., the seeds) are especially toxic. In fact, they are the source of the infamous poison, ricin. Their toxicity can be problematic for young children and curious pets, so keep this in mind when considering where (if whether) to plant this eye-catching specimen. If you still want to grow castor bean plants, you can lessen their danger by cutting off the flowers and disposing of them, thereby preventing seed formation.
Death from ricin poisoning can occur between 36 and 72 hours of exposure, so time is of the essence. If you notice any of the below symptoms of poisoning, contact the proper emergency services right away.
Symptoms of Poisoning in Humans
- Difficulty breathing
- Tightness in chest
- Low blood pressure
- Blood in urine or stool
- Pain of the skin or eyes
- Kidney, liver, or spleen failure
Symptoms of Poisoning in Animals
- Abdominal pain
- Bloody diarrhea
- Excessive drooling
- Loss of appetite
- Mouth pain
- Sudden collapse
- Shaking or trembling