Grow Striking Castor Bean with These Essential Planting Tips (2024)

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.

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 or in groups for a tropical effect in the back of beds or near water. 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.

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.

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 bean is drought-tolerant once established.

Temperature and Humidity

Castor bean is a tropical plant that won’t survive in temperatures below 32°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.

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 or soaked.

1. Soak the seeds overnight in cold water before planting.
2. Start seeds indoors in 4-inch pots filled with potting mix or plat them directly in garden soil after the last frost.
3. Plant the seeds 1 to 1 ½ inches deep.
4. Keep the soil evenly moist. The seeds germinate in 1 to 3 weeks.
5. Harden the seedlings off before transplanting them outside after the last frost.

How to Eliminate Castor Bean

Medium plants should be removed with a weed wrench. However, if the plant is small, then it can be removed with a shovel or by hand. Since it is toxic, make sure you are wearing protective clothing when handling it and deposit the seeds, which are the most toxic part of the plant, in a landfill.

Types of Castor Bean

'Carmencita Bright Red' Castor Bean

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

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

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 green. 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

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

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.