Fundamental Facts
HARDINESS: Tender
PREFERRED SOIL pH: Adaptable
PREFERRED SOIL TYPE: Average, well-drained
PREFERRED LIGHT: Sun
ATTRIBUTES: Large, fast-growing plants; use as screen, at back of border, with tall companion plants
SEASON OF INTEREST: Midsummer to frost
FAVORITES: 'Carmencita' for burgundy leaves; 'Carmencita Pink' for pink flowers; 'Impala' for maroon seed pods
QUIRKS: All parts of the plant are toxic if ingested
GOOD NEIGHBORS: Amaranth, morning glory, sunflower, zinnia
WHERE IT GROWS BEST: Full sun, in warm, well-drained soil
POTENTIAL PROBLEMS: Wind can topple large plants
CRITTER RESISTANCE: Excellent
SOURCE: Bedding plants, seeds
DIMENSIONS: 8 ft (2.4 m) tall, 4 ft (1.2 m) wide
Castor Bean in the Landscape
Fast-growing castor bean plants are worth growing for their immense star-shaped burgundy or green leaves, which cast a spell of jungle magic over any garden. Castor bean's strange clusters of bright red or pink flowers open in late summer and are followed by round pods covered with colorful spines, which contain bean-sized mottled seeds.
In a warm summer with plenty of rain, these dramatic plants can reach 10-12 ft (3-3.7 m) in height, with leaves up to 2 ft (0.6 m) in diameter that may be bright green or bronze red, depending on the variety. If you need a fast-growing screen to block bad views or a giant self-supporting hedge, or you want to form a leafy background for a flower bed, no other annual or perennial will do the job like castor bean plants. And because the stems are spaced rather far apart, sufficient light reaches the insides of the plants to accommodate vines such as morning glories, which twine around the central stem for surprising special effects. Castor bean plants also work well as a leafy backdrop for larger-than-life flowering annuals such as love-lies-bleeding (amaranth), tall zinnias, or sunflowers.
Comely Castor Bean
You'll find that seed companies offer a few cultivars, but any gardener who grows castor beans will surely have a few seeds or volunteer seedlings to share. In the spring you can purchase bedding plants from garden centers. The Carmencita' variety has very large deep mahogany leaves and unusually large bright red flowers. 'Carmencita Pink' has pink flowers, while the flowers of Impala mix are carmine with maroon, followed by maroon seed pods.
Growing Castor Bean
Start castor beans indoors 8 weeks before your last frost, taking care to wear gloves when handling the poisonous seeds. In areas with warm and long summers, you can plant the seeds directly outdoors. Soak the seeds for 24 hours in warm water before planting them 1 in (2.5 cm) deep in moist soil. Keep the soil moist and between 60° and 70°F (16°-21°C). Sprouting, or germination, should begin within 15 days, and the seedlings can be planted out after the soil warms in late spring.
Castor beans do not require fertile soil, but the garden spot where you plant them should be loose and friable for at least 12 in (30.5 cm) deep so that the roots of seedlings can grow deeply. If their roots cannot penetrate the soil, a summer storm can blow these tall-growing beauties down. Space or thin seedlings to 3 ft (1 m) apart in the garden.
Because castor bean plants are poisonous, a strong case can be made for not growing them in gardens visited by children. As an extra safety precaution, you can snip off the flowers before they set seed pods and dispose of them, since the seeds are the most toxic part of the plants.
To their credit, pests of all kinds avoid castor beans, and also may ignore nearby plants. The seeds are widely believed to repel moles when dropped into mole tunnels.
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