Ricinus communis: planting, sowing, cultivation

Description and Botany

The Common castor bean or Ricinus communis is a perennial herbaceous plant with a woody stump from the family Euphorbiaceae. Native to fallow lands and rocky slopes in North-East Africa and South-West Asia, it is a perennial of tropical and subtropical climates that is primarily grown as an annual in our temperate climates. Frost-sensitive, it dies at -3°C and may only survive in the ground in regions where it does not freeze. The genus Ricinus comprises only one species: Ricinus communis, which is available in about ten varieties, such as ‘Carmencita’ with dark red foliage or ‘Zanzibar’ with green fruits and very large leaves.

In its native habitat, it can form a bush nearly 10 meters tall, but in our climates, it maintains more modest dimensions. Fast-growing, this large perennial reaches between 0.90 and 2 m in the ground within a single season. It has a bushy and upright habit. The ‘Zanzibar’ variety is one of the tallest, capable of climbing to 3 to 4 m in regions where frost does not occur.

The castor bean is characterised by the beauty of its foliage. Its dark branches are spectacular! It develops large, palmately lobed green or purple leaves depending on the variety. Alternate, deeply palmatilobate (5 to 7 pointed lobes), and serrated, they can measure up to 20 cm in diameter, sometimes more. They resemble an open palm, the leaf of a plane tree, or that of a maple, revealing purple or white veins. These lush leaves are connected by long petioles to robust, knotted stems that are also coloured.

The foliage is sumptuous from spring to autumn. This ample foliage continuously changes colour, starting with red when juvenile, then bright green to purplish in the typical species. It takes on more or less purplish hues, wine-red, bright orange-red, or bronze depending on the cultivars, and appears green in ‘Zanzibar’. Glossy, the foliage has a shiny texture.

The flowering is not particularly remarkable. Discreet, it occurs in summer, from July to October. Red and yellow in colour, the rather insignificant flowers are grouped in pyramidal racemes at the ends of the stems. Male flowers form yellowish tufts at the base, while female flowers are clustered at the top. However, the fruiting is quite decorative. The flowers are followed by clusters of oval fruits in capsules composed of three prominent shells, covered in soft thorns. They display a scarlet red or are sometimes pink in ‘Carmencita pink’, contrasting with the foliage.

At maturity, these fruits explode, releasing seeds that are projected several metres away. They will be dispersed by wind or birds, leading to spontaneous sowing. They are highly toxic if ingested.

The ricin contained in most of the plant is very toxic. The seeds, resembling blood-engorged ticks, contain a powerful alkaloid that was once used to create a deadly poison. Castor oil is extracted from it, a non-food oil, now used in the cosmetic, pharmaceutical, and even automotive industries. It is among the most widely used industrial vegetable oils in the world. It is particularly included in cosmetic care products. Once stripped of its toxic enzyme, it can be used for its benefits for skin and hair; it is reputed to promote eyelash growth!

Main varieties

Ricinus communis Honolulu

A sumptuous variety of castor oil plant interesting for its fiery colours! Guaranteed spectacle in a summer bed!

• Flowering time September to November
• Height at maturity 2 m

See the product sheet

Ricin de Zanzibar

It's one of the tallest! It exceeds 2 m in just a few weeks. It stands out with its very decorative green foliage and fruits.

• Flowering time July to September
• Height at maturity 2 m

See the product sheet

Castor bean planting

Where to plant it?

En dépit de son aspect robuste, the castor bean n’est pas rustique. C’est pourquoi, dans la plupart de nos jardins, it is grown as an annual plant, not surviving the slightest frost. Dans le Sud de notre pays, dans les régions les plus abritées, il est possible de le cultiver comme une plante vivace. On peut protéger la souche par un épais paillis de feuilles installé à l’automne. Choisissez a sunny location, car c’est une plante tropicale qui aime le plein soleil et la chaleur. Réservez-lui un endroit sheltered from strong, cold winds that could cause its stems to bend. En plein vent, il aura besoin d’un tuteurage. Offrez-lui a good deep garden soil, rich in humus, well-drained and remaining relatively cool durant toute la période de croissance.

Il se plaira dans de nombreux jardins abrités. Il est intéressant pour créer un décor éphémère dans un massif d’été exotic très coloré. Dans le jardin, le ricin commun permet d’étoffer rapidement une zone laissée libre. Au regard de sa grande stature il trouvera sa place au soleil, at the back of large perennial beds not exposed to draughts. Il apportera une belle touche exotique tout en mettant en valeur les plantes voisines. Il s’impose également in large pots on the terrace pour y aménager un décor dépaysant, ce qui vous permettra de le remiser dans la véranda en hiver pour le conserver.

Castor bean planted in a flower bed and in a pot on a terrace.

When to plant the castor bean?

La plantation du ricin commun se fait au printemps, in May or June. Nos mini-mottes seront installées en extérieur dès que les risques de gelées sont définitivement écartés.

How to plant it?

In the ground

Respectez une distance de plantation de 1 m environ entre chaque pied. We suggest adding well-decomposed compost, as it appreciates soils rich in organic matter.

• Dig a hole 2 to 3 times wider than the plug plant
• In heavy soil, add clay balls or pumice at the bottom of the planting hole to improve drainage
• Add manure or decomposed compost if the soil is poor
• Plant in the planting hole
• Fill in with a mixture of good potting soil, compost, and garden soil
• Place stakes if necessary and replace the soil, pressing down lightly
• Water generously

In a pot

Prévoyez de l’installer dans a large pot with a drainage hole of at least 50 cm in diameter as this large perennial has a significant wind resistance. Good drainage is essential.

• Spread a good layer of gravel or clay balls at the bottom of the container
• Plant in a mixture of good potting soil, compost, and garden soil

Castor bean planted in a predominantly red flower bed (© Gwenaelle David)

Sowing castor seeds

Sowing castor bean seeds is done in March or April in a warm sheltered environment. Soak the seeds in warm water for 24 hours before sowing.

• Sow one seed per bucket (or in a heated mini greenhouse) filled with good sowing compost and sand
• Cover the seeds with 1 cm of compost
• Lightly firm down
• Water generously with a fine spray and keep moist throughout the germination period
• Maintain a minimum temperature of 20°C
• Transplant into larger pots when the young plants have grown sufficiently
• Replant in the garden when all risk of frost has passed

Caring for Castor Bean Plant

In Open Ground

This annual requires no special maintenance. Water twice a week to keep the soil moist throughout the summer, especially during periods of intense heat. However, avoid excess moisture. The soil can be kept cool with a mulch in summer. Stake if exposed to windy conditions.

Uproot the plants in autumn. If you live in a region with a warm climate, you can leave the plant in place, but protect it from cold snaps with a thick mulch. Ensure to make annual additions of organic matter to maintain good humus content in the soil. Clean the clump at the end of winter by trimming the dry parts.

In Pots

Water generously in summer, never allowing the substrate to dry out between waterings. This plant is very hungry: add fertiliser to the watering can every 15 days during the growth period.

As soon as the first frosts arrive, bring the plant indoors to protect it from frost in a conservatory or greenhouse where the temperature does not drop below 0°C. In winter, reduce watering by allowing the soil to dry out almost completely and stop fertiliser applications.

Top up with potting soil and compost once a year in spring. As soon as the risk of frost has passed, you can take it back out into the garden to enjoy the beautiful season.

Diseases and potential pests

Castor oil plant does not really experience problems with diseases and pests. When grown indoors, it can occasionally be attacked by red spider mites that thrive in dry conditions. As a preventive measure, regularly mist the foliage.

When conditions are very humid and warm, it can be susceptible to Botrytis and powdery mildew, fungi that are favoured in confined environments with warm and rather humid air.

Multiplication

As we have seen, it is possible to sow castor seeds to multiply them (check our section dedicated a little higher up “Sowing castor seeds”). You can harvest the seeds when they are ripe (the capsules turn brown and open), then store them in a paper bag for sowing in spring. But remember that toxic ricin is mainly found in the seeds, keep them well away from children.

Les bienfaits des graines de ricin sont nombreux. Elles sont principalement connues pour leurs propriétés médicinales et cosmétiques. Voici quelques-uns de leurs avantages : 1. **Propriétés laxatives** : L'huile extraite des graines de ricin est un puissant laxatif naturel, souvent utilisée pour soulager la constipation. 2. **Hydratation de la peau** : L'huile de ricin est un excellent hydratant, aidant à adoucir et à nourrir la peau, tout en favorisant la cicatrisation des blessures. 3. **Renforcement des cheveux** : Elle est souvent utilisée dans les soins capillaires pour renforcer les cheveux, favoriser leur croissance et réduire la casse. 4. **Antimicrobien** : Les graines de ricin possèdent des propriétés antimicrobiennes, ce qui les rend utiles pour traiter certaines infections cutanées. 5. **Anti-inflammatoire** : L'huile de ricin peut aider à réduire l'inflammation et soulager les douleurs articulaires lorsqu'elle est appliquée localement. 6. **Soutien au système immunitaire** : Certaines études suggèrent que les graines de ricin peuvent renforcer le système immunitaire grâce à leurs propriétés antioxydantes. Il est important de noter que les graines de ricin doivent être utilisées avec précaution, car elles contiennent de la ricine, une substance toxique. L'huile de ricin, cependant, est généralement considérée comme sûre lorsqu'elle est utilisée correctement.

Castor seeds are contained within bristly shells, and they are toxic and deadly if ingested. Cold or hot pressing yields a non-food oil that is safe and has medicinal properties with numerous benefits. Castor oil is ancient, with its use dating back thousands of years, to 4000 BC! Highly nourishing and used externally, it is ideal for strengthening and nourishing hair, eyelashes, eyebrows, and nails. It also possesses emollient, hydrating, antimicrobial, and antifungal properties, very useful for the skin. In traditional Chinese medicine, castor oil is renowned for alleviating rheumatic and muscular pain. Rest assured, commercial oils are free from ricin!

Seeds and castor oil

Associate

With its beautiful spiky scarlet fruits and its ample, lush palmate leaves, Castor Oil Plant is perfect for filling out a tropical border in summer. Its large lobed leaves will blend perfectly into a tropical-themed setting. It allows for the creation of stunning ephemeral displays at the back of borders or in large pots on the terrace.

As a backdrop, create an exotic scene by pairing it with other plants that have ample foliage, such as banana plants (Musa basjoo), a Chinese palm (Trachycarpus fortunei), and a Colocasia, another stunning tropical plant. To create harmony, add some bushes and perennials with dark foliage, such as Colocasia ‘Black Magic’, Albizia ‘Summer Chocolate’ in mild climates, Black Elder ‘Black Lace’, and Astilbe ‘Chocolate Shogun’. You will add floral touches in warm shades with crocosmias, some Cannas, kniphofias, gladioli, and daylilies; these plants will hide its base, which tends to become bare easily.

You will also achieve very beautiful contrasting combinations by pairing the purplish foliage of the castor oil plant with some tall blue agapanthus. In pots, you can surround it with shorter perennials like begonias, and small annuals such as petunias, pansies, and some Coleus.

Ricinus communis, Colocasia ‘Black Magic’, Canna ‘Red King Humbert’, and Albizia julibrissin ‘Summer Chocolate’