How to Grow Castor Oil Plant

Curated by Claudia Shannon / Research Scientist / Honayst

Ricinus, the castor oil plant, brings exotic structure to gardens in summer with its dramatic foliage. The bold, glossy palmate leaves, reddish-purple in colour, are the main attraction. It looks great teamed with hot coloured plants and contrasting foliage in an exotic or jungle-style border.

A native of tropical climates, ricinus is usually grown as an annual in the UK and suits both containers and borders.

The bold, glossy palmate leaves, reddish-purple in colour, are the main attraction.
Where to plant castor oil plant

Grow in containers in free draining, soil-based compost in full sun, or in a well-drained sunny border. Plants grown on poorer soils tend to produce more flowers and the foliage is less abundant.

How to plant cast oil plant

Please note, the seeds are poisonous, so wear gloves when handling. Seeds must be sown early in the year, and ideally soaked for a few hours beforehand. Fill individual pots with seed compost, sow the ricinus seeds and place in a heated propagator to germinate. Seeds need 15 to 20°C and should germinate in two to six weeks. Pot on when seedlings are large enough to handle and move outdoors or plant up into containers or borders when all danger of frost has passed.

Looking after castor oil plant

All parts of Ricinus communis are highly toxic so it’s very important to wear gloves when handling – it can irritate skin and eyes. Water plants regularly and feed with a liquid fertiliser every month. Plants are generally fast growing – Ricinus communis reaches 8-12m in height in tropical climes, but in a British garden, it is much smaller. Plants may need staking. Deadhead flowers if you don’t want to collect the seed. At the end of the season, discard plants on the compost heap, or move plants to a covered area under glass to grow on as a conservatory shrub.

Propagating castor oil plant

Ricinus communis produces greenish-yellow flowers and spiny round seedpods. You can save the seed but they are notoriously toxic. Bearing this in mind, you might choose to deadhead the fluffy blooms before seeds set.

Ricinus: problem solving

Ricinus is generally disease-free outdoors. If grown under glass, it may fall prey to the usual greenhouse pests such as red spider mite.

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