Article by Dean Ravenscroft, Ph.D. - Updated 1st Feb 2024
At a Glance: Ricinus communis - (Castor Oil Plant)
- Plant Characteristics: Known for its large, star-shaped leaves that can vary in color from green to deep burgundy. Produces spiny seed pods and small flowers. A fast-growing plant that adds a tropical feel.
- Growing & Care: Prefers full sun and well-drained soil. It is drought-tolerant once established but performs best with regular watering and feeding.
- Tips for New Gardeners: Handle with care as all parts of the plant, especially the seeds, are highly toxic if ingested. Suitable for adding drama to garden spaces or as a focal point in a container.
The Ricinus communis plant is usually referred to as the Caster Bean or the Caster Oil Plant.
It is thought to be native to the tropical regions of Africa. It has naturalized many parts of the USA and may be deemed as an invasive plant in some areas, so please take care not to grow it in these areas if you are considering adding it to your garden.
Also be aware that it is an extremely poisonous plant, especially the ricin rich seeds.
In the garden it is usually grown as a specimen species, container plant, or as a shrubby annual.
It is often grown for its attractive large palm like leaves that change color as the plant gets older.
The fruits are also showy. As mentioned above this is a very poisonous plants, it is not recommended to grow this plant if you have small children or pets.
Castorbean photograph by Andrey Zharkikh, CC.
This seeds of this plant are pressed to produce castor oil. This oil is often used in the production of soaps, perfumes, paints, dyes, nylon, and numerous other goods. It is a rich source of ricinoleic acid and thus is used for feed stocks.
Gardeners tend to use cultivars of this plant for focal interest. Commonly grown cultivars of Ricinus communis include 'Carmencita', large palm leaves, red flower spikes; 'Carmencita Pink', pink seed pods; 'Gibsonii', red tinge to the leaves, scarlet seed pods; 'Carmencita Bright Red', purple leaves, red seed pods; and 'Red Spire' tall cultivar to 10 feet (3 m), bronze leaves.
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Quick Growing and Care Guide
- Scientific Name: Ricinus communis
- Common Name (s): Castor Oil Plant, Castor Bean
- Growing Zone (USA / UK Hardiness): 9 to 11 (Castor bean can be grown as an annual from zone 3)/ H2
Plant Details
- Life Cycle / Plant Type: Suckering Shrub, Perennial but usually grown as an annual as it is not frost tolerant.
- Plant Height: Garden varieties 6 to 10 feet (2 to 3 m); wild type can reach 40 feet (13 m) in its natural tropical habitat, but full growth is usually stopped by frost.
- Plant Spread: 1.5 to 4 feet (75 to 120 cm)
- Blooms: Summer and Autumn
- Flower Details: Green/yellow. Terminal panicle.
- Leaf Foliages: Palmate, Glossy. Alternate. Long stalks. Many varieties have leaves that change colour as the plant mature. Green, dark green, reddish brown, purple. Purple turning dark green, Bronze turning dark green.
- Fruit: Showy. Spiny. Capsule. Green, Red-purple. Seeds are warped and poisonous.
Growing Conditions
- Best Light Conditions: Full sunlight.
- Suitable Soil Types: Rich loams for best results. Poor soils result in poorer leaves but a greater number of flowers.
- Soil Soil Moisture: medium to dry.
- Sowing, planting, and Propagation: Soak seeds for about 24 hours prior to sowing. Sow seeds at a depth of 1/4 inch (6 mm) towards the end of spring (well after the last frost). Seeds germinate at about 70°F (21°C).
- Care: Highly poisonous plant (always use gloves), remove seed capsules by pinching before they have chance to set seed. Leaves may cause skin irritations. Other than that it is a pretty low maintenance plant. Provide a stake in windy areas.
Further Information
- Best used for: Ornamental plants for gardens that do not see children. Sometimes seen as a decorative plant in parks
- Miscellaneous: Although often called the Castor bean, it is not a member of the legume family and therefore not a true bean. Castor oil is sourced from the seeds, which contain ~40 to 60% oil. Seeds are dispersed by ants. Attracts butterflies and moths. People may be allergic to its pollen. Sap causes skin rashes. Considered to be the most commonly grown poisonous plant. If you ingest the plant seek medical attention immediately. Approximately two million tonnes of castor beans are produced for commercial use each annum, with India being far the biggest producer.
- Family: Euphorbiaceae (Spurge)
- Closely related species and genera: Euphorbia Spurge; Ghost Plant; Ricinus Genus
- Further Reading and References used for this Ricinus communis growing guide: Castor Oil; NC State Nursery
I hope that you enjoyed this guide on how to grow Ricinus communis plants. You may also enjoy the following Gardener's HQ growing guides: How to grow Aleurites moluccana and Bean plants.
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