Gardening Flowers Annuals How to Plant and Grow Castor Bean Use caution around this pretty but highly toxic plant. By Nadia Hassani Nadia Hassani Nadia Hassani is a gardening and food writer with more than two decades of hands-on gardening experience in vegetable and fruit gardening, landscaping with native plants, and garden design. Learn about BHG's Editorial Process Updated on April 28, 2023 In This Article View All In This Article Where to Plant Planting Tips Care Pests and Problems Propagation Types Companion Plants FAQ Trending Videos Close this video player Native to Africa, the castor bean is a dramatic tropical plant. Its large glossy green leaves with five to 11 pointed lobes look like fingers on an open hand. Some varieties sport bronze or burgundy foliage. Spikes of small, cup-shaped, greenish-yellow flowers appear from June to October. The seedpods emerge as bright red or pink, then dry to a dull brown before splitting open. As attractive as castor bean is, before planting it, take into consideration that all parts of this plant are highly toxic to humans and pets. Castor Bean Overview Genus Name Ricinus communis Common Name Castor Bean Plant Type Annual, Perennial Light Sun Height 3 to 10 feet Width 2 to 4 feet Flower Color Pink, Red, Yellow Foliage Color Blue/Green, Purple/Burgundy Season Features Summer Bloom Special Features Low Maintenance Zones 10, 11, 9 Propagation Seed Problem Solvers Deer Resistant, Good For Privacy Where to Plant Castor Bean Castor bean requires a location with full sun and rich, well-drained, neutral to slightly acidic soil (pH 6.0-7.3). Choose a spot that is protected from strong wind which can make the plant snap and damage the leaves. Its towering height makes castor bean an eye-catching backdrop in the garden and adds intrigue to bland borders. In frost-free climates like Zones 9-11, it can become a small tree. Castor bean can be planted as a specimen for or in groups for a tropical effect in the back of beds or near water a pond or fountain. It can also be planted in a row to create a seasonal screen. Wherever you plant it, make sure it is out of reach of children and pets. In tropical climates, castor bean has escaped cultivation and spread aggressively in disturbed areas such as in fields, pastures and along roadsides and railroads. It is invasive in the southeastern and southwestern United States. How and When to Plant Castor Bean Plant castor bean seeds in the late spring after all danger of frost has passed. In cooler climates, start the seeds indoors 6 to 8 weeks before the last frost date and transplant the seedlings. Space the plants 4 feet apart. Castor bean can reach 6 to 10 feet in a single growing season, which means it may need support. 8 Pretty but Dangerous Garden Plants to Grow with Caution Castor Bean Care Tips Light Castor bean can handle part shade, but it needs full sun to achieve the best height and flowering. Soil and Water Castor bean thrives in rich, evenly moist, well-drained soil. Castor is drought-tolerant once established. Temperature and Humidity Castor bean is a tropical plant that won’t survive in temperatures below 32 degrees F. In cooler climates, it is therefore grown as an annual that concludes its life cycle with the first frost. It tolerates high humidity well. Fertilizer Because castor bean grows so rapidly, it needs monthly fertilization, starting with the seedlings in the spring. Use a granular slow-release balanced fertilizer and scatter it at least 5 inches away from the base of the plant. Pruning You can prune the plant to contain its vigorous growth. Also, consider cutting off the flower stalks before they mature to prevent them from setting seeds. Potting and Repotting Castor Bean Castor bean can be grown in containers, but they must be large, at least 12 to 14 inches tall and wide, and made of a heavy material (glazed ceramic or terra-cotta) so they don’t topple over under the considerable weight of the plant. Make sure the container has large drainage holes. To give the container more weight and stability, add a layer of pebbles or small rocks at the bottom before filling it with a combination of potting soil and compost. Keep in mind that container plants need more frequent watering and fertilizer than inground plants. If you planted caster bean in a container of adequate size, it won’t require repotting during its single growing season. Pests and Problems With the exception of spider mites, which can appear in hot, dry weather, castor bean has no major pest or disease problems. How to Propagate Castor Bean Castor bean is propagated from seed. The seeds have a hard shell that needs to be nicked. You can also soak the seeds overnight in cold water before planting. You can start your seeds indoors in 4-inch pots filled with potting mix or plat them directly in garden soil after the last frost. Either way, plant the seeds 1 to 1 ½ inches deep and keep the soil evenly moist. The seeds germinate in 1 to 3 weeks. Harden the seedlings off before transplanting them outside after the last frost. Types of Castor Bean 'Carmencita Bright Red' Castor Bean Getty Images This well-branched cultivar of Ricinus communis has marron foliage and bright red seed pods. It grows 5 to 6 feet tall. 'Carmencita Pink' Castor Bean Getty Images The bright pink seed pods and pinkish-red stems are an attractive change from the typical bright red of other castor bean types. It reaches 5 to 6 feet in height. Castor Bean Companion Plants Canna Kritsada Panichgul Canna is a bold plant featuring clustered, flaglike blooms in a brilliant color array on tall stems. Recent flower breeding has created canna foliage even showier than the petals, with variegated leaf combinations of orange, yellow, and greens. Dwarf cannas are also available for container gardening and other small spaces. Cannas provide architectural interest in summer borders and flourish along a pond's damp margins. Zones 7-10 Hibiscus Bill Stites Huge, showy blooms are the hallmark of the hibiscus family, whether the flying saucers on hardy perennial hibiscus (zone 4-9), the Hawaiian charmers of the tropical hibiscus (zone 9-11), or the frilly-flowered Rose of Sharon (zone 5-9) that grows into a large shrub or small tree. Hibiscus blooms boast a fantastic array of colors, vastly widened through hybridizing, and they draw hummingbirds. The newer, dark-leaf introductions are wonderful architectural fillers in container gardens. Mexican Sunflower Peter Krumhardt Attract butterflies with giant, bold, beautiful Mexican sunflower. Plant this warm-season annual from seed directly in the ground and watch it soar. It can hit up to 5 feet in weeks with big, lush foliage and smaller but still showy flowers in sunset colors. Put a cluster in the back of the border to give it height and drama. Many of the taller types need staking to keep them upright. Guide to Growing Tropical Plants Frequently Asked Questions Do castor bean plants come back every year? Botanically castor bean is a perennial that comes back every year but only in climates with mild winters. Below zone 9, it is grown as an annual. Where is castor bean native to? The plant is native to tropical east Africa, including Ethiopia. It has naturalized in tropical and subtropical areas around the world and is considered an invasive plant in many places, including Australia and parts of the United States. Can I compost the castor bean plant after it has died in the fall? Because of its toxicity, the plant should only be composted in municipal composting plants, where the compost reaches high temperatures and is monitored. Otherwise, the safe way to dispose of the plant (and its beans) is in the household trash. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Better Homes & Gardens is committed to using high-quality, reputable sources—including peer-reviewed studies—to support the facts in our articles. Read about our editorial policies and standards to learn more about how we fact check our content for accuracy. "Castor Bean Plant." ASPCA. "Ricinus communis." North Carolina State University Cooperative Extension. "Invasive Plant Atlas of the United States." "Castor bean fall disposal or compost." Ask Extension.